6.1 Project Parameter D R A F T Water Quality Requirements 6 Treatment... · D R A F T D R A F T D R A F T DRAFT REPORT REVISED SEPTEMBER 2005 6-1 6.0 Treatment Alternatives 6.1 Project

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DRAFT REPORT REVISED SEPTEMBER 2005 6-1

6.0 Treatment Alternatives

6.1 Project Parameter

6.1.1 Water Quality Requirements As presented in Section 5, the main regulatory controls over the recycled water quality are imposed and enforced through permitting by CDHS and the Santa Ana Regional Board based on public health and environmental quality-driven objectives. Tables F-1 through F-3 of Appendix F summarize the definitions of different treatment levels required for different recycled water uses. Accordingly, undisinfected secondary, disinfected secondary and disinfected tertiary treated recycled waters are allowed for irrigation use and various other applications. As shown in Table F-3, the regulated quality parameters are total coliform and turbidity for recycled water uses other than groundwater recharge. This information is summarized in Table 6-1.

CDHS regulates the drinking water quality, and for artificial groundwater replenishment of groundwater basins with domestic water aquifers, the CDHS sets limits to control the quality of the recycled water. The Santa Ana Regional Board sets quality objectives for groundwater, inland surface waters, enclosed bays and estuaries, the Santa Ana River, and ocean waters in the Santa Ana River Basin region. CDHS Title 22 recycled water quality requirements and the Santa Ana Regional Board recycled water quality objectives that apply to the BBARWA are summarized in Table 6-2.

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TREATMENT ALTERNATIVES


TABLE 6-1 CURRENT RECYCLED WATER QUALITY REQUIREMENTS FOR RECYCLED WATER USES OTHER THAN ARTIFICIAL GROUNDWATER REPLENISHMENT

Parameters Units

Undisinfected Secondary

Effluent

Disinfected Secondary-23

Recycled Water

Disinfected Secondary-2.2

Recycled Water

Disinfected Tertiary Recycled Water

Turbidity NTU Not required Not required Not required

For conventional filtration process

<2 NTU within a 24-hour period

<5 NTU, 95% of the time within a 24-hour period <10 NTU at any time

For membrane Processes (MF, NF, UF, or RO)

<0.2 NTU, 95% of the time within a 24-hour period <0.5 NTU at any time

Total Coliform

CFU / 100 mL Not required

< 23 MPN/100 mL for 7-day

average < 240 MPN/mL in

more than one sample in a 30-

day period

< 2.2 MPN/100 mL for 7-day

average < 23 MPN/mL in more than

one sample in a 30-day period

< 2.2 5-log removal of MS-2 bacteriophage or for the

polio virus < 2.2 MPN/100 mL for 7-day

average < 23 MPN/mL in more than

one sample in a 30-day period

< 240 MPN/mL

CFU colony-forming unit MPN most probable number NF nanofiltration NTU nephelometric turbidity unit

TABLE 6-2 CURRENT CDHS TITLE 22 AND SANTA ANA REGIONAL BOARD RECYCLED WATER QUALITY REQUIREMENTS FOR ARTIFICIAL GROUNDWATER REPLENISHMENT

Classification Constituent Units Secondary

Effluent CDHS Limits

Regional Board Limits

Color Color Units 20 ---- <15

Odor T.O.N. 64 ---- <3.0

Turbidity NTU 1.7 <2.0, <0.2(a) <5

Corrosivity --- ---- non-corrosive

Specific Conductance µmhos/cm 740 (<900)

General Physical Properties

pH pH units 8.0 ----- 6 to 9 (a) 0.2 NTU, 95% of the time within a 24-hour period with a membrane technology (for complete information see Table 6-1.)

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Total Coliform MPN/100 mL <2.2a <2.2 Microbiological

Virus Inactivation Log or % 5.0 or 99,999a ----

Bicarbonate mg/L 320

Carbonate mg/L 260

Total Alkalinity mg/L 260

Calcium mg/L 56

Chloride mg/L 51 (<250) <10

Fluoride mg/L 0.5 <2.0 <2.0

Hydroxide mg/L ND

Magnesium mg/L 23

Nitrate (as N) mg/L 0.5 ---- <5

Nitrite (as N) mg/L 1.0

Total Nitrogen mg/L 2.6 <10.0a, <5.0b ----

Total Anions me/L 7.51

Total Cations me/L 7.80

Potassium mg/L 11

Sodium mg/L 65 ---- <20

Sulfate mg/L 40 (<250) <20

Total Dissolved Solids mg/L 430 (<500) <300

General Minerals and Ions

Total Hardness mg/L CaCO3 240 ---- <225 aAs an average bAt a maximum frequency

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Perchlorate µg/L ND

Cyanide mg/L ND <0.15 <0.15

Other Ions

Bromide mg/L 0.064

Aluminum µg/L 63.0 <1,000 (<200) <200

Antimony µg/L ND <6 <6

Arsenic µg/L ND <50 <50

Barium µg/L ND <1000 <1000

Beryllium µg/L ND <4 <4

Cadmium µg/L ND <5 <5

Total Chromium µg/L ND <50 <50

Cobalt µg/L ---- <200

Copper µg/L ND <1,300 (<1,000) <1000

Iron µg/L 43 (<300) <300

Lead µg/L ND <15 <50

Manganese µg/L 13 (<50) <50

Mercury µg/L ND <2 <2

Nickel µg/L ND <100 <45,000

Selenium µg/L ND <50 <5

Silver µg/L ND (<100) <50

Thallium µg/L ND <2 <2

Total Silica mg/L 24

Metals and Metalloids

Zinc µg/L 55 (<5,000) <5,000

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Radium-226 + Radium-228

pCi/L <5 <5.0

Radioactivity, gross alpha

pCi/L <15 <15.0

Tritium pCi/L <20,000 <20,000

Strontium-90 pCi/l <8 <8.0

Radioactivity, gross beta pCi/L <50 <50.0

Radioactivity

Uranium pCi/L <20 <20.0

Miscellaneous Asbestos MFL <7 <7.0

Bromate mg/L 10

Chloramines mg/L 4

Chloride mg/L (<250)

Chlorine mg/L 4

Chlorine dioxide mg/L 0.8

Chlorite mg/L 1

Bromodichloro- methanea

µg/L 80

Bromoform4 µg/L ND 80

Chloroform4 µg/L ND 80

Dibromochloro-methanea

µg/L 80

Monochloroacetic acid5 µg/L 60

Dichloroacetic acid5 µg/L 60

Trichloroacetic acid5 µg/L 60

Monobromoacetic acid5 µg/L 60

Disinfection By-products

Dibromoacetic acid5 µg/L 60 a80 µg/L MCL is for summation of 4 trihalomethanes (Total THMs) b60 µg/L MCL is for summation of 5 haloacetic acids (HAAs)

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Foaming Agents (MBAS)

mg/L ND (<0.5) <0.05 Organics

Total Organic Carbon mg/L 6.5 <16 -----

Alachlor µg/L ND <2 <2

Aldrin µg/L ND

Chlorothalonil µg/L ND

Dieldrin µg/L ND

Endrin µg/L ND <2 <2

Lindane µg/L ND <0.2 <0.2

Methoxychlor µg/L ND <30 <30

Toxaphene µg/L ND <3 <3

Chlordane µg/L ND <0.1 <0.1

Heptachlor µg/L ND <0.01 <0.01

Heptachlor Epoxide µg/L ND <0.01 <0.01

Hexachlorobenzene µg/L ND <1 <1

Hexachloro-cyclopentadiene

µg/L ND <50 <50

Propachlor µg/L ND

Organochlorine Pesticides

Polychlorinated Biphenyls (PCBs)

µg/L ND <0.5 <0.5

2,4-D µg/L ND <70 <70

2,4,5-TP Silvex µg/L ND <50 <50

Bentazon µg/L ND <18 <18

Dalapon µg/L ND <200 <200

Dicamba µg/L ND

Dinoseb µg/L ND <7 <7

Pichloram µg/L ND <500 <500

Organochlorine Herbicides

Pentachlorophenol µg/L ND <1 <1

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Atrazine µg/L ND <1 <1

Molinate µg/L ND ---- <20

Simazine µg/L ND <4 <4

Thiobencarb µg/L ND <70 <70

Butachlor µg/L ND

Diazinon µg/L ND

Dimethoate µg/L ND

Diuron µg/L ND

Prometryn µg/L ND

Bromacil µg/L ND

Metolachlor µg/L ND

N-P Pesticides

Metribuzin µg/L ND

Ethylene Dibromide (EDB)

µg/L ND ---- <0.05 Fumigants

Dibromochloro-propane (DBCP)

µg/L ND <0.2 <0.2

Aldicarb µg/L

Aldicarb Sulfone µg/L ND

Aldicarb Sulfoxide µg/L

Oxamyl µg/L <50 <50

Carbofuran µg/L <18 <18

Carbaryl µg/L

3-Hydroxycarbofuran µg/L ND

Carbamates

Methomyl µg/L

Miscellaneous Glyphosate µg/L ND <700 <700

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Endothall µg/L ND <100 <100

Diquat µg/L ND <20 <20

Pesticides

2,3,7,8-TCDD Dioxin pg/L ND <0.00003 <0.00003

Benzo(a)pyrene mg/L ND <0.2 <0.2

Di(2-ethylhexyl) adipate mg/L ND <400 <400

Semivolatile Organic Compounds

Di(2-ethylhexyl) phthalate

mg/L ND <4 <4

Volatile Organic Compounds

Benzene µg/L ND <1 <1

Carbon tetrachloride µg/L ND <0.5 <5

1,2-Dichlorobenzene µg/L ND <60 <60

1,4-Dichlorobenzene µg/L ND <5 <5

1,1-Dichloroethane µg/L ND <5 <5

1,2-Dichloroethane µg/L ND <0.5 <0.5

cis-1,2-Dichloroethene µg/L ND <6 <6

trans-1,2-Dichloroethene

µg/L ND <10 <10

1,1-Dichloroethene µg/L ND <5 <6

1,2-Dichloropropane µg/L ND <5 <5

cis-1,3-Dichloropropene µg/L ND <0.5

Ethylbenzene µg/L ND <300 <300

Methylene Chloride µg/L ND ---- <5

Methyl tert-butyl-ether (MTBE)

µg/L ND <13 (<5) <5

Chlorobenzene µg/L ND <70 <70

Styrene µg/L ND <100 <100

1,1,2,2-Tetrachloroethane

µg/L ND <1 <1

Tetrachloroethene µg/L ND <5 <5

1,2,4-Trichlorobenzene µg/L ND <5 <5

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1,1,1-Trichloroethane µg/L ND <200 <200

1,1,2-Trichloroethane µg/L ND <5 <5

Trichloroethene µg/L ND <5 <5

Trichlorofluoro-methane µg/L ND <150 <150

1,1,2-Trichloro-1,2,2-trifluoroethane

µg/L ND <1200 <1200

Toluene µg/L 0.85 <150 (<1,000) <150

Vinyl chloride µg/L ND <0.5 <0.5

Xylenes (Total) µg/L ND <1750 <1750

Dibromomethane µg/L ND

1,1-Dichloropropene µg/L ND

1,3-Dichloropropane µg/L ND

Chloromethane µg/L ND

Bromomethane µg/L ND

1,1,1,2-Tetrachloroethane

µg/L ND

Chloroethane µg/L ND

2,2-Dichloropropane µg/L ND

o-Chlorotoluene µg/L ND

Volatile Organic Compounds (continued)

p-Chlorotoluene µg/L ND

Bromobenzene µg/L ND

Dichlorodifluoro-methane

µg/L ND

1,2,4-Trimethylbenzene µg/L ND

1,2,3-Trichlorobenzene µg/L ND

n-Propylbenzene µg/L ND

n-Butylbenzene µg/L ND

Naphthalene µg/L ND

Hexachlorobutadiene µg/L ND

1,3,5-Trimethylbenzene µg/L ND

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p-Isopropyltoluene µg/L ND

tert-Butylbenzene µg/L ND

sec-Butylbenzene µg/L ND

Bromochloromethane µg/L ND

Bromodichloro-methane µg/L ND

Chlorodibromo-methane µg/L ND

1,3-Dichlorobenzene µg/L ND

1,4-Dioxane µg/L ND

2-Butanone(MEK) µg/L ND

4-Methyl-2-Pentanone(MIBK)

µg/L ND

Bis(2-Chloroethyl)Ether µg/L ND

Di-Isopropyl Ether µg/L ND

Ethyl tert-Butyl Ether µg/L ND

Isopropylbenzene µg/L ND

tert-Amyl Methyl Ether µg/L ND

Volatile Organic Compounds (continued)

tert-Butyl Alcohol µg/L ND

Notes: a0.2 NTU, 95% of the time within 24 hours period with a membrane technology (For complete information see Table 3.5-2.) bAs an average cAt a maximum frequency d80 µg/L MCL is for summation of 4 THMS (Total trihalomethanes) e60 µg/L MCL is for summation of 5 HAAS (Haloacetic acids) fValues in parenthesis refer to Secondary MCL otherwise primary MCLs µmhos micromhos MBAS methylene blue-activated substances MPN Most Probable Number ND Non-Detect NTU Nephelometric Turbidity Unit T.O.N. threshold odor number

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6.1.2 Current Secondary Treatment and Effluent Quality The BBARWA system is composed of a 4.89-mgd-capacity secondary wastewater treatment plant, 14.6 miles of sewer pipeline, and 1.5 miles of existing recycled water pipeline. The average daily flow treated by the BBARWA WWTP is approximately 2.2 mgd. The BBARWA uses approximately 13 afy of the treatment plant effluent for irrigation, construction compaction and dust control, and wildlands firefighting.

In the Big Bear Valley, the BBARWA interceptor system collects wastewater from DWP, the BBCCSD, and the County of San Bernardino. The BBARWA operates three main lines: LPS force main, which services the City of Big Bear Lake wastewater system; North Shore Interceptor, which services the county wastewater system; and the BBARWA Trunk Line, which services the BBCCSD wastewater system and conveys flow from the North Shore Interceptor to the treatment plant. All of the wastewater flows to the BBARWA WWTP located at Baldwin Lake. Figure 6-1 shows the existing treatment units of the BBARWA WWTP. The BBARWA Regional Wastewater Treatment Plant provides secondary treatment of influent, which consists of the following:

• Preliminary Treatment – Consisting of screening of solids with bar screens, grit removal, and landfill disposal of solids.

• Secondary Biological Treatment – Consisting of oxidation ditches using mechanical aeration, achieving organic material stabilization, nutrient removal via “Symbio” process and pathogen reduction.

• Secondary Sedimentation Treatment – Consisting of solids settlement in clarifiers, pumping of waste activated sludge (WAS) to a dissolved air floatation (DAF) system, and returning activated sludge to the oxidation ditches.

• WAS Thickening – Consisting of a DAF System that skims sludge for sludge dewatering using a belt filter press and a system that pumps the filtrate to the oxidation ditches

• Sludge Dewatering – Consisting of either a belt filter press or sand/asphalt drying beds that produces belt filter cake for disposal and return filtrate to the oxidation ditches.

• Sludge Disposal – The dewatered solids are hauled to either Nursery Products composting facility in Adelanto, the Synagro composting facility in Corona, or incinerated at the Mitsubishi cement plant in the Lucerne Valley. The Nursery Products and Synagro plants compost the solids to produce commercially available compost. The Mitsubishi cement plant burns the solids in their kilns to reduce harmful NOX emissions from their smokestacks.

• Water Reclamation – Effluent from the plant is used for irrigation, construction, and wildlands fire-fighting purposes. Recycled water is stored onsite in either a storage tank or an existing unused chlorine contact chamber.

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Part of the secondary effluent from the BBARWA WWTP is discharged to the Lucerne Valley to be used for agricultural irrigation. The 480-acre Lucerne Valley discharge site is bounded by Old Woman’s Springs Road (SR-247) to the north, Dallas Avenue to the east, Foothill Road to the south, and Camp Rock Road to the west. The secondary effluent is used on this site to irrigate alfalfa fields. The alfalfa is used to feed horses, sheep, and other livestock. Three monitoring wells are located on the property and are tested regularly to ensure that the groundwater is not being adversely affected by the secondary effluent.

The BBARWA WWTP secondary effluent water quality and discharge requirements for Discharge Points No. 001 and 002 are summarized in Table 6-3, and Discharge Point No. 003 is summarized in Table 6-4. Discharge Points No. 001, No. 002 and No. 003 refer to secondary effluent without disinfection, secondary effluent with disinfection and tertiary effluent with disinfection. In addition to discharge permit water quality parameters, the BBARWA monitors the following parameters in following frequency:

• Hardness (Quarterly, at Discharge Point No. 001) • Sodium (Quarterly, at Discharge Point No. 001) • Chloride (Quarterly, at Discharge Point No. 001) • Sulfate (Quarterly, at Discharge Point No. 001) • Total Phosphorus (Monthly, at Discharge Point No. 001) • Specific Conductivity (Daily, at Discharge Point No. 001 and No. 003) • EPA Priority Pollutants- Metals (Annually, at Discharge Point No. 001) • EPA Priority Pollutants- Volatile Organic Compounds (Annually, at Discharge Point

No. 001)

According to Tables 6-2 through 6-4, BBARWA WWTP fully satisfies effluent discharge requirements for each discharge point. Even though the TIN concentrations are less than 10 mg/L on a monthly average basis (Tables 6-3 and 6-4) and are meeting NPDES discharge requirements, the TIN values well exceeded 10 mg/L in some occasions. Table 6-5 shows the nitrogen removal performance of the WWTP for January 2001 to December 2002 and January 2004 to June 2004. In each period, a TIN concentration of up to 19 mg/L was reported. To be able to develop treatment solutions that will meet the CDHS total nitrogen (TN) limit of 10.0 mg/L or less for groundwater replenishment, a better understanding of the current operation and effluent quality is needed.

BBARWA Recycled Water Master Plan±

K:\BBARWA\plots\MasterPlanRevisionTwo\Fig_X_Existing_Treatment_Plant.mxd 08/23/05

1 - Bar Screens

3 - Oxidation Ditch

4 - Secondary Clarifier

5 - Concrete Equalization Basin (previously chlorine contact basins)

6 - Holding Pond ("Horseshoe Ponds")

7 - Emergency Storage Pond

8 - Main Effluent Pump Station

9 - Sand Drying Bed

10 - Dissolved Air Flotation Thickener (DAFT)

12 - Asphalt Drying Bed

14 - Carbon Odor Scrubber

15 - 600 KW Natural Gas Generator

2 - Aerated Grit Chamber

11 - Belt Filter Press (BFP)

13 - Truck Loading

Figure 6-1 - Existing BBARWA WWTP Layout

17 - Auxiliary Effluent Pump Station

16 - 550 KW Generator

18 - Pilot MF/RO System

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14

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TABLE 6-3 BBARWA Effluent Water Quality – and Discharge Limitations for Discharge Points No. 001 And 002

Parameters Units

Effluent Concentration

(April 19, 2002)

Average Effluent Concentration

September 2003a

Average Effluent Concentration (January 2004 to June 2004)a

Secondary Effluent

Discharge Limitationsa,b

pH SU 8.0 7.4-8.3 7.8 6.0-9.0

Biochemical Oxygen Demand (BOD5)

mg/L NM 8.0 5.0 30 (45)


lbs/day NM 330c 204c 1223 (1,835)

Total Suspended Solids (TSS)

mg/L NM 7.1 9.1 30 (45)


lbs/day NM 290c 371c 1,223 (1,835)

Total Inorganic Nitrogen (TIN)

mg/L 2.1 3.8 5.7 10

Total Dissolved Solids (TDS)d

mg/L 430 419 409 550

Total Dissolved Solids (TDS)d

lbs/day 17,000c 16,700c 22,430

Coliformd MPN/ 100 mL

23e

240f Notes: aAll values are monthly average unless otherwise mentioned bValues in parentheses refer to weekly average values and calculated based on a design capacity of 4.89 mgd clbs/day values are calculated based on a design flow of 4.89 mgd dOnly for Discharge Point No. 002 eMedian concentration of the coliform in disinfected effluent using the bacteriological results of the last seven days for which analysis have been completed fNo more than one sample in any 30-day period

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TABLE 6-4 BBARWA Effluent Water Quality – and Discharge Limitations for Discharge Point No. 003

Parameters Units

Effluent Concentration

(April 19, 2002)a

Average Effluent Concentration

September 2003a

Average Effluent Concentration (January 2004 to June 2004)a

Secondary Effluent

Discharge Limitationsa,b

pH SU 8.1 7.4-8.3 7.8 6.0-9.0


mg/L NM 8.0 5.0 20, (30)


lb/day NM 67c 42c 167, (250)


mg/L NM 7.1 9.1 20, (30)


lb/day NM 593 763 167, (250)

Total Inorganic Nitrogen (TIN)

mg/L 2.1 3.8 5.7 10

Total Dissolved Solids (TDS)

mg/L 430 419 409 550

Total Dissolved Solids (TDS)

lb/day 3,600c 3,500c 3,400c 4,600c

Turbidity NTU 0.21 NM NM <0.5 at any time

Coliform MPN/ 100 mL

NM NM NM 2.2d

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240f Notes: aAll values are monthly average unless otherwise mentioned bValues in parentheses refer to weekly average values and calculated based on a flow of 1.0 mgd clbs/day values are calculated based on a design flow of 1.0 mgd dMedian concentration of the coliform in disinfected effluent using the bacteriological results of the last seven days for which analysis have been completed eNo more than one sample in any 30-day period fNo sample shall exceed a coliform value of 240 MPN/100 mL

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TABLE 6-5 BBARWA EFFLUENT LINE MONITORING

Parameters Units

Reporting Year 2001 – 2002

January to December

Reporting Year 2004

January to June

Ammonia-N mg/L <0.5 – 11 <0.5 – 4.5

Nitrate-N mg/L <0.01 – 19 0.152 – 16.2

Total Inorganic Nitrogen (TIN) mg/L 0.5 – 19 1.1 – 18.9

Total Kjeldahl Nitrogen (TKN) mg/L <1.0 – 8.2 1.0 – 5.0

Note:

TIN = Nitrite-N+ Nitrate-N + Ammonia-N

6.1.3 Product Water Requirements The projected WWTP average flow of 2,100 afy (1.88 mgd) limits the ultimate recycle water capacity.1 The ultimate recycled water quantity available for supply to recycled water users is approximately 1,600 afy; corresponding to 1.45 mgd of product water flow. To be able to match funding and meet the immediate and interim recycled water needs, the decision was made to plan the recycled water production capacity in two different phases. In Stage I, up to 1,000 afy (0.9 mgd) recycled water would be produced. In Stage II (Ultimate Phase), a total of 1,600 afy recycled water would be produced.

6.2 Potential Treatment Methods Advanced wastewater treatment is defined as the additional treatment needed to remove suspended, colloidal, and dissolved constituents remaining after conventional secondary treatment. Individual pollutants can be grouped into four broad categories requiring removal. These are:

1. Residual organic-inorganic colloidal and suspended solids

2. Dissolved organic constituents (TOCs, VOCs, surfactants)

3. Dissolved inorganic constituents (ammonia, phosphorus, TDS, calcium, and magnesium, chloride)

4. Biological constituents (bacteria, viruses, and protozoan cysts/oocysts)

1 1,600 afy is calculated based on MF and RO treatment options and using water recoveries of 90 and 85%, respectively (2,100 afy*0.9*0.85=1,600 afy)

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Typical advanced treatment technologies that can produce recycled water meeting tertiary quality requirements imposed by the CDHS are summarized in Table 6-6. The latest Treatment Technology Report for Recycled Water published in September 2004 by the Division of Drinking Water and Environmental Management that operates under CDHS lists the treatment technologies that are approved or are under evaluation for use in the generation of recycled water. The California Water Recycling Criteria (December 2000) defines “Disinfected Tertiary Recycled Water” as wastewater that meets the quality criteria presented earlier by achieving the following treatment requirements:

• Has been coagulated and filtered through natural undisturbed soils or a bed of filter media at a rate less than 5 gallons per minute per square foot (gpm/sf) in mono, dual, or mixed media filters, or 2 gpm/sf in traveling bridge automatic backwash filters.

OR

• Has been passed through MF, UF, nanofiltration (NF), or RO membrane treatment, meeting the turbidity requirements.

AND

• Disinfected using chemicals or UV light

The treatment technologies that are listed in the aforementioned technology report cover a variety of filtration technologies offered by a number of vendors. The acceptance of each treatment unit is conditional with acceptance based on the specifications and operational conditions of the unit, in most cases. Also, some treatment methods may require an additional demonstration period prior to approval and final installation.

6.2.1 Nitrogen Removal Based on the limited amount of secondary effluent quality data, to meet DHS nitrogen requirements, the BBARWA advanced treatment facility will need additional nitrogen removal beyond that achieved in the secondary treatment step. To accomplish the additional nitrogen removal, optimization of the existing secondary treatment along with a follow-on treatment step can be very effective. TN is composed of ammonia nitrogen, nitrate and nitrite nitrogen, and organic nitrogen. The best way to reduce TN values is to optimize secondary treatment to yield either minimized ammonia or nitrate/nitrite concentrations, so that the remaining nitrogen can be taken out in the tertiary treatment nitrogen removal units. Two of these systems that can be used at the BBARWA WWTP are fluidized bed reactors (FBR) and biological aerated filters (BAF).

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TABLE 6-6 ADVANCED TREATMENT PROCESSES TO REMOVE RESIDUAL CONSTITUENTS FOUND IN TREATED WASTEWATER

Residual

Constituent UV Chemical

Disinfection FBR BAF Depth

Filtration SurfaceFiltration

Micro and Ultrafiltration

ReverseOsmosis

Electro-dialysis

Carbon Adsorption

Chemical Precipitation or

Oxidation Colloidal and Suspended Solids

Suspended Solids X X X X X X X X X

Colloidal Solids X X X X X X X X X

Particulate Organic Matter X X X

Organic Matter

Total and Dissolved Organic Carbon

X X a X X X X

Refractory Organic Compounds X X X

Volatile Organic Compounds X X X

Dissolved Inorganic Matter

Ammonia X X X X X

Nitrate X X X

Phosphorus Xb Xb X X X

Total Dissolved Solids X X

Biological

Bacteria X X X X X

Protozoan Cysts and Oocysts X X X X X X X X

Viruses X X X c X X

Note: a Only remove particulate/colloidal fraction of TOC b Requires chemical addition prior process c Virus removal is a function of membrane type and can range from 0.5 to 2 log. Up to 2 Log removal can be achieved via Ultrafiltration

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6.2.1.1 Fluidized Bed Reactor

A fluidized bed reactor (FBR) is a fixed-film reactor column that fosters the growth of microorganisms on a hydraulically fluidized bed of media, usually sand or activated carbon. The fluidized media provides an extremely large surface area on which a film of microorganisms can grow, providing a high concentration of biomass, usually 2 to 5 times greater than in conventional activated sludge systems. In this process, the thickness of biofilm is controlled to optimize the density of the particles and minimize their overflow with the effluent. Figure 6-2 provides a schematic of a typical FBR system developed for the purpose of removal of ammonia and nitrate nitrogen from the feed stream. In the case of the BBARWA, the first FBR (i.e., nitrification reactor) may not be needed, if the secondary treatment process produces a sufficient amount of nitrified effluent.

Legend:

1. Feed tank2. Nitrogen gas diffuser3. Feed to nitrification reactor4. Nitrification reactor with GAC5. Recirculation line6. Influent line to denitrification

tank7. Sampling port8. Nitrified feed tank9. Air diffuser10. Nutrient feed

11. pH meter12. DO meter13. Flowmeter14. Denitrification reactor with

GAC15. Sampling port16. Water bath17. Recirculation line18. Denitrified effluent19. Nitrogen gas collection

channel20. Mass flowmeter for nitrogen

gas

FIGURE 6-2. NITRIFICATION/DENITRIFICATION FBR SYSTEM SCHEMATIC

The advantages of the FBR process include:

• Small footprint • Capability to handle hydraulic and organic shock loads • Capability to provide good ammonia removal (depending on the ammonia load)

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The disadvantages of using the FBR process include:

• Potential for requirement for several FBRs in series depending on the influent wastewater flows and loads

• Potential for media carry over in effluent

• Reduced treatment efficiency with high total suspended solids (TSS) in feed

• Dependence of the system performance on oxygen transfer efficiency

• Backwash requirement

6.2.1.2 Biological Aerated Filter

BAF units are commonly used as a polishing step at WWTPs where effluent nutrient limitations require strict discharge quality control. There are two major types of BAF units available: Biofor™ and Biostyr®.

Biofor™ is a biological, submerged filter containing a fixed, dense granular bed with influent wastewater flowing in an upward direction. The system employs proprietary media that serve as biological contactors as well as a filter, eliminating the need for separate clarification, which results in space savings. The media supporting a strong, thin biomass (1 to 2 millimeters [mm]) not only provides a surface for the biomass but also captures the solids. Co-current flows (air and water traveling the same direction) aid in the distribution of air throughout the media and eliminate gases from binding the filter bed. The process has four major components:

• Single-layer carrier material Biolite • Specific aeration system (i.e., Oxazur) • Upflow distribution of air and water • Unique washing sequences

Biolite, an expanded clay material, has a high specific surface area (400 to 500 square feet per cubic foot [ft2/ft3]), low density, and good resistance to attrition. Typical media depths are 10 to 13 feet. Oxazur diffusers are made of flexible membranes.

The co-current upflow distribution of air and water enables homogeneous suspended retention and biomass growth throughout the media without short-circuiting or entrapping gas bubbles. Typical hydraulic loading range is 1.5 to 8.5 gpm/sf. Figure 6-3 is a schematic of a Biofor™ BAF identifying its various components.

Advantages of the Biofor™ BAF process include:

• Compact layout • Simple operation • Elimination of final clarifiers (low effluent TSS) • Potentially good ammonia removal (95 percent or higher based on low ammonia loads)

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Disadvantages of using the Biofor™ BAF process include:

• High capital cost • Potential for requirement for several BAFs in series depending on influent wastewater

flows and loads Media may carry over in effluent

1. Distribution Nozzles2. Pipe Gallery3. Monoflor Underdrain4. Oxazur Air Diffusers5. Tranquilizer Baffle

FIGURE 6-3. BIOLOGICAL AERATED FILTER UNIT SCHEMATIC (BIOFORTM UNIT SHOWN)

Biostyr® process consists of upflow filtration through submerged and floating fine-granular media called Biostyrene. Biostyrene media with high specific surface area provides attachment for bacteria. Perforated cell roof slab retains the media during filtration. Filtration compacts the media rather than expanding it, thereby enhancing the capture of suspended materials. Counter-backwashing eliminates excess biomass and suspended solids that have been filtered. During backwash, the downward flow expands the media, and gravity aids in flushing solids from the bottom layer of media. The backwash water from the reservoir above the filters eliminates the need for backwash pumping.

Advantages of Biostyr® over Biofor™ include:

• Media are retained by a cell roof, which reduces media carryover • Separate washwater and washing pumps are not required

Disadvantages of Biostyr® over Biofor™ include:

• Gravity backwash may not be effective as conventional backwash • Compressible media may increase head loss and reduce filtration time

6.2.2 Depth Filtration Depth filtration involves the removal of particulate material suspended in liquid by passing the liquid through a filter bed made of a granular or compressible filter medium (Metcalf and Eddy, 2003). Depth filtration is used to achieve supplemental removals of suspended

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solids from wastewater. It is a conditioning step prior to disinfection of the filter effluent that also is used as a pretreatment step for membrane filtration.

The performance of filters depends on influent quality. Several large-scale and pilot-scale applications have shown that filtration can produce an average effluent turbidity of 2 nephelometric turbidity units (NTU) or less if filter influent turbidity is less than 5 to 7 NTU (10 to 17 mg/L TSS). The studies also shown that chemical addition usually is required if influent turbidity is greater than 5 to 7 NTU (Metcalf and Eddy, 2003). The decision on the type of filtration system to be used often based on plant-related variables, such as land available for filtration process, duration of filtration (e.g., seasonal or year-round), and time and money available for construction.

The selection of filtration technology usually entails the following considerations:

• Filter to be used, proprietary or individually designed (manufacturer design and the complete filter unit in proprietary filters)

• Filtration rate (typical range is 2 to 8 gpm/sf; Schreiber Fuzzy Filter can handle filtration rates up to 30 gpm/sf)

• Filtration driving force (gravity versus pressure)

• Number and size of filter units (the surface area requirement is based on the peak filtration and peak plant flow rates)

• Backwash water requirement (in semicontinuous operation, the filter is operated until the effluent quality starts to deteriorate or head loss becomes excessive; neither turbidity breakthrough nor terminal head loss occurs with filters operated continuously)

Advantages of depth filtration include:

• Proven and common technology • Relative ease of operation • Inexpensive capital and operation costs compared to microfiltration and reverse osmosis

Disadvantages of depth filtration include:

• Large footprint (includes, filter and backwash water storage)

• Loss of filter medium

• Turbidity breakthrough may occur even though terminal head loss has not been reached

• Performance may vary depending upon filter influent quality

• Usually requires chemical back-up facility

• Produces low quality effluent compared to membrane filtration processes

Depth filters may produce water quality suitable for use as recycled water for irrigation purposes following a disinfection step. However, a coagulation step may be required ahead of the filters depending upon filter performance and filter influent quality.

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6.2.3 Membrane Filtration Membranes form a highly selective barrier to small constituents with a typical size of 0.001 to 1.0 micrometer (µm) depending on the membrane pore size. An illustration of commonly encountered wastewater constituents and corresponding size distributions are given in Figure 6-4. Typical membrane processes used in recycled water treatment are:

• Microfiltration (MF) • Ultrafiltration (UF) • Nanofiltration (NF) • Reverse osmosis (RO) • Electrodialysis (ED)

FIGURE 6-4. SIZE DISTRIBUTION OF COMMONLY ENCOUNTERED MATERIAL AND FILTRATION APPLICABILITY

The characteristics of membrane technologies used in wastewater treatment applications are summarized in Table 6-7.

A common feature of MF, UF, NF and RO membrane technologies is that hydraulic pressure is applied to achieve the separation. Electrodialysis involves the use of electromotive force to separate ions by ion-selective membranes.

Reverse Osmosis

Ultrafiltration Particle Filtration

Nanofiltration Microfiltration

Separation Process

Metal Ion

RReellaattiivvee SSiizzee OOff

CCoommmmoonn MMaatteerriiaallss

Microns 0.001 0.01 0.1 1.0 10 100 1000

Approx Molecular Weight

100 200 1,000 20,000 100,000 500,000 1 MM 5 MM

Note: 1 micron (micrometer) = 4 x 10-5 inches = 1 x 104 Angstrom units ©2004-Koch Membrane Systems

Synthetic Dyes

Aqueous Salt Milk Proteins

Gelatin

Endotoxin Pyrogen

Virus

Lactose (Sugars)

Colloidal Silica

E-Coat Pigment

Red Blood Cells

Bacteria

Oil Emulsion

Blue Indigo Dye

Cryptosporidium

Giardia Cyst Human Hair

Whole Broth Cells

Fat Micelles

Activated Carbon

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TABLE 6-7 TYPICAL CHARACTERISTICS OF MEMBRANE PROCESSES USED IN WATER RECYCLING

Membrane Process

Typical Separation Mechanism

Operating Pore Size

nm

Typical Operating

Range, µm

Operating Pressure

kPa

Rate of Flux

gal/ft2d Permeate

Description Constituents

Removed

Microfiltration Sieve >50 0.08-2.0 7-100 10-50 Water plus dissolved solutes

TSS, turbidity, protozoan,

oocysts, some bacteria, viruses

Ultrafiltration Sieve 2-50 0.01-0.05 70-700 10-35 Water plus

small molecules

Macromolecules, colloids, most bacteria, some

viruses, proteins

Nanofiltration Sieve+

diffusion+ exclusion

<2 0.001-0.01 500-1,000 10-16

Water plus very small molecules,

ionic solutes

Small molecules,

some hardness, viruses

Reverse Osmosis

Diffusion+ exclusion

<2 0.0001-0.001 850-7,000 8-16

Water plus very small molecules,

ionic solutes

Very small molecules,

color, hardness, ions

Electrodialysis

Ion separation

with selective membrane

<2 NA Water plus ionic solutes Ionize salt ions

Source: Metcalf and Eddy, 2003

6.2.3.1 Microfiltration and Ultrafiltration

MF and UF can be used instead of depth filtration to reduce turbidity, remove residual suspended solids, and partially reduce pathogen concentrations as a primary (physical) disinfection step prior to chemical disinfection or as a pretreatment step for NF or RO. Figure 6-5 shows the typical arrangement of MF units at a membrane facility.

The advantages of using MF or UF units include:

• Reduction of treatment chemical usage

• Small footprint (50 to 80 percent less space than depth filtration)

• Low cost of operation labor

• Low-pressure design is cost competitive with conventional wastewater coagulation/filtration processes

• Good choice for the treatment of raw water with variable turbidity problems

• Removes protozoan cysts, oocysts, bacteria, and variable amounts of viruses

• Provides low-fouling feedwater to NF and RO

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FIGURE 6-5. A TYPICAL ARRANGEMENT OF UF/MF MEMBRANE FILTRATION UNITS (TALL MEMBRANES SHOWN)

The disadvantages of using MF or UF units include:

• Moderate energy cost • Requires chemicals to clean membranes and maintain productivity • May require pretreatment (coagulation) to prevent fouling • Higher residuals waste volumes compared to granular and cloth media filters • Requires membrane replacement about every 5 to 10 years

Typical applications of MF and UF include:

• Treatment of surface water and groundwater under the influence (of surface water) for drinking water and industrial process water

• Treatment of waste water into "gray" or process water

• Pretreatment to NF and RO on hard, brackish surface waters, seawater, and wastewater effluents

6.2.3.2 Nanofiltration and Reverse Osmosis

In addition to use in softening and demineralization/desalination of ground and surface waters to produce drinking water, NF and RO are used to treat MF and UF pretreated secondary effluent for reuse applications such as direct injection and surface recharge of potable aquifers. Disinfection credits are typically awarded to NF and RO commensurate with their salt and/or TOC rejection. Compared to RO, NF has seen significantly less application in water recycling because of lower removals of inorganic and organic dissolved compounds. Figure 6-6 shows a typical RO membrane system.

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(a)

(b)

FIGURE 6-6. TYPICAL REVERSE OSMOSIS MEMBRANE UNITS: (a) ZENORO LF FROM ZENON; (b) KOCH RO

The advantages of using RO units include:

• Superior effluent quality (removes nearly all dissolved constituents, both inorganic and organic, including endocrine disruptors and related compounds)

• Excellent removal of nutrients

• Effectively removes all pathogens

• Disinfection credit

The disadvantages of using RO units include:

• Works best on groundwater, low solids surface water, or pretreated wastewater

• Higher capital costs than conventional and low-pressure membrane processes (MF and UF)

• Expensive to operate compared to conventional treatment and MF and UF

• Produces high waste volumes and requires appropriate disposal of high-salinity waste stream (concentrate)

• Subject to fouling by bacteria and organics

• Requires chemicals for membrane cleaning

6.2.3.3 Electrodialysis/Electrodialysis Reversal

ED is a process in which solutions are desalted or concentrated electrically. Salts in water dissociate into positively and negatively charged ions. The key to the ED process is a semipermeable barrier, which allows passage of either positively charged ions (cations) or

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negatively charged ions (anions) while excluding passage of ions of the opposite charge. These semipermeable barriers are commonly known as ion exchange, ion-selective, or electrodialysis membranes. The product water does not pass through a membrane barrier in these processes, so they are used primarily for desalting and demineralization applications. Electrodialysis reversal (EDR) electrodes and membranes would require replacement once a year and every 5 years, respectively. Figure 6-7 is a simplified representation of the ED/EDR fundamental process.

FIGURE 6-7. NEGATIVELY AND POSITIVELY CHARGED MEMBRANES OF ED/EDR SYSTEMS

The advantages of using EDR units include:

• Potentially higher recovery than other membrane processes depending on feedwater quality

• Lower fouling potential because product water moves along the membrane surface as opposed to through the membrane surface

• Ability to clean and reuse EDR membranes

The disadvantages of using EDR units include:

• Not all constituents, such as boron or silica, are removed

• Effective at TDS concentrations less than 9,000 parts per million only

• Not recognized by CDHS as a Title 22 treatment technology because EDR does not provide a treatment barrier

• May require serial trains depending on the feed quality

• Quality of product water can be lower than other membrane processes

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6.2.4 Cloth Media Filtration Cloth media filters are designed for a variety of tertiary treatment applications. This proven technology produces reuse-quality effluent and is an accepted filtration technology under California Title 22. Each cloth media filtration system uses a special fiber medium, such as a nylon fiber material, that provides consistent removal of very fine particulate matter. Cloth media filters are low-head systems that can be gravity fed. Each system is designed to backwash automatically upon water differential while maintaining continuous filtration during backwash. Typical backwash is less than 2 to 3 percent with a quick recovery time of less than 3 minutes, compared to other typical filters that can take up to 20 minutes. A variation of the cloth media filtration is a patented medium that consists of nylon fibers arranged in a pile construction on a polyester backing material (Aqua Aerobic Systems). Pile cloth media is designed for the AquaDisk® filter (Figure 6-8) and is used exclusively for filtering municipal and industrial wastewaters.

High pressure

spray washmanifold

Backwashmanifold

Controlpanel

Backwash/sludgepump

Sludgevalve

Backwashvalves

FilterDisks

Drive

Effluentchannel

Overflowchannel

Filtrateheader

InfluentWeir

(a)(b)

FIGURE 6-8. SCHEMATIC OF CLOTH MEDIA FILTRATION UNITS: (a) AQUADISK® FILTER; (b) KRUGER DISCFILTER

The advantages of using cloth media filtration units include:

• Small footprint and modular design • Low capital cost • Continuous operation • Low backwash recovery • No sand, underdrains, or tubes • Easily expandable • High solids-loading capacity • No backwash holding tank required • Low power requirements • Simple design and simple to operate • Coagulant not required in California since filters are Title 22 approved without chemical

addition

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The disadvantages of using cloth media filtration units include:

• Short track • Limited experience upstream of UV • Replacement of cloth media recommended every 6 years • Some moving parts • Only two manufacturers

6.2.5 Other Physical-Chemical Techniques Other common advanced treatment techniques are adsorption (activated carbon), distillation, and chemical precipitation. The main applications of adsorption (granular or powdered activated carbon) process is in the removal of organic compounds in water and as a main treatment unit or polishing step for further removal of organics. Carbon regeneration or replacement is needed to replenish treatment capacity of the “spent” carbon beds.

Distillation, similar to the RO process, can produce high-quality effluent. The primary application of distillation technologies is for the production of potable water from seawater, predominantly in the Middle East. However, distillation is highly energy intensive and typically requires a source of thermal energy to be cost effective. It is not cost effective for low-salinity waters such as wastewater effluents. Lastly, chemical precipitation can effectively remove colloidal particles, as well as soluble constituents like phosphorus, but the performance is impacted heavily by the water quality (ionic strength, pH, and organic content). It requires chemical storage and feed facilities, and spent chemical and sludge disposal issues must be resolved.

6.3 Treatment Waste Handling A number of the advanced treatment technologies summarized above generate waste streams that need to be further treated or disposed. Table 6-8 summarizes typical concentrate generation rates for the selected treatment processes. There are a number of advanced technologies for the treatment and handling of waste streams from advanced treatment processes. These methods are effective and reliable; however, the treatment method selection is to be based upon the disposal requirements and the specific needs of the community. BBARWA investigated these technologies were investigated, and the results of the ensuing evaluation were summarized in Analysis and Identification of Alternatives to Address Disposal of RO Membrane Process Concentrated Waste Stream (BBARWA, 2003).

6.4 Selection of Advanced Treatment Technologies CDHS strongly recommends that when a particular filtration technology is considered for recycled water treatment, its appropriateness for the particular water being treated be extensively evaluated and demonstrated. The technologies discussed herein are widely used in recycled water applications; however, numerous vendors supply products under each given technology. Each product performs differently based on the characteristics of the wastewater effluent and may require pilot testing.

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Market assessment results presented in Section 3 revealed that four major markets for recycled water in the BBARWA service area would be:

• Artificial Surface Groundwater Replenishment • Industrial/Commercial/Construction Activities • Environmental Impoundment Urban Irrigation

TABLE 6-8 BRINE GENERATION RATE FOR SELECTED ADVANCED TREATMENT PROCESSES

Is Brine Generated? Typical Quantity of Brine Generated

Treatment Method Yes No (for Each 1 mgd Treated)

Standard Treatment a Depth Filtration Microfiltration c 0.02 to 0.06 Ultrafiltration c 0.10 to 0.15 Nanofiltration 0.15 to 0.20 Reverse Osmosis 0.15 to 0.30 d

Electrodialysis 0.10 to 0.20 Ion Exchange 0.08 Ultraviolet Light Advanced Oxidation Processes b

Chemical Oxidation a. Represents basic secondary treatment required to meet regulations. b. Advanced Oxidation Processes: Strong oxidant is added to UV reactors to form OH* radical. c. Microfiltration and Ultrafiltration waste stream (i.e., filtrate stream) can be returned to main plant and should

not be considered brine. Neutralization of the backwash water may be required prior to recycling or disposal.

d. Use of reverse osmosis for seawater desalination can have rejection rates of up to 50 percent. Source: BBARWA, 2003

The permitting requirements for the listed types of use for recycled water were summarized in Section 5 and are in Appendix F, along with other regulatory requirements that will be imposed on this recycled water program by federal and state agencies. The water quality requirements for various recycled water uses and artificial surface groundwater replenishment were listed earlier in this section (see Tables 6-1 and 6-2). Because the treatment requirements are not the same for all uses, the treatment units must be selected and designed with consideration given to the need for product water streams treated to different levels of quality. Product water can be drawn at different points of the treatment train, depending on the need and the types of users at different times of the year.

Groundwater replenishment has the strictest water quality criteria. Therefore, the treatment method selected should be able to remove any existing or emerging pollutants of concern, such as pharmaceuticals and personal care products (PPCPs) and endocrine-disrupting compounds (EDCs). Because the existing laboratory techniques have not yet been

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standardized, especially at low detection levels, these compounds potentially will be controlled by maintaining a low TOC level (e.g., less than 0.5-mg/L).

The potential treatment alternatives that will be commensurate with the recycled water market assessment results are listed below. Disinfection can be achieved by chemical addition or UV light. Each technology is accepted by the CDHS, given that appropriate demonstration studies and contact requirements will be included in the design of the units in accordance with National Water Research Institute (NWRI)/American Water Works Association Research Foundation (AWWARF) guidelines. Accordingly, the treatment alternatives listed below, and shown in corresponding Figures 6-9 through 6-18, include either chemical disinfection or UV light as the last treatment step.

Alternative 1-A: Nitrogen Removal with BAF + Rapid Mix + Direct Filtration with Granular-Activated Carbon (GAC) + Cartridge Filters + EDR Membranes + Chemical Disinfection

RRaappiiddMMiixx DDeepptthh

FFiillttrraattiioonnCChheemmiiccaallDDiissiinnffeeccttiioonn

SSeeccoonnddaarryyEEfffflluueenntt

BBAAFF

PPrroodduuccttWWaatteerr

EEDD RRMMeemmbbrraanneess

CCaarrttrriiddggeeFFiillttrraattiioonn

FIGURE 6-9. SCHEMATIC ILLUSTRATION OF ALTERNATIVE 1-A

Alternative 1-B: Nitrogen Removal with BAF + Rapid Mix + Direct Filtration w/ GAC + Cartridge Filters + EDR Membranes + UV Disinfection


FFiillttrraattiioonn


BBAAFF




UUVVDDiissiinnffeeccttiioonn

FIGURE 6-10. SCHEMATIC ILLUSTRATION OF ALTERNATIVE 1-B

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Alternative 2-A: Nitrogen Removal with FBR and GAC + Rapid Mix + Direct Filtration + Cartridge Filters + EDR Membranes + Chemical Disinfection


FFBBRR



FFiillttrraattiioonnCChheemmiiccaallDDiissiinnffeeccttiioonn




Alternative 2-B: Nitrogen Removal with FBR and GAC + Rapid Mix + Direct Filtration + Cartridge Filters + EDR Membranes + UV Disinfection



FFBBRR

UUVVDDiissiinnffeeccttiioonnRRaappiidd

MMiixx DDeepptthhFFiillttrraattiioonn




Alternative 3-A: Rapid Mix + Direct Filtration + Cartridge Filters + NF + Chemical Disinfection



FFiillttrraattiioonn CChheemmiiccaallDDiissiinnffeeccttiioonn


NNFFMMeemmbbrraanneessCCaarrttrriiddggee



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Alternative 3-B: Rapid Mix + Direct Filtration + Cartridge Filters + NF + UV Disinfection






NNFFMMeemmbbrraanneessCCaarrttrriiddggee



Alternative 4-A: Screen Filters + MF + RO + Chemical Disinfection


SSccrreeeennFFiilltteerrss

CChheemmiiccaallDDiissiinnffeeccttiioonn


MMFFMMeemmbbrraanneess

RROOMMeemmbbrraanneess


Alternative 4-B: Screen Filters + MF + RO + UV Disinfection




MMFFMMeemmbbrraanneess




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Alternative 5-A: Screen Filters + UF + RO + Chemical Disinfection



CChheemmiiccaallDDiissiinnffeeccttiioonn


UUFFMMeemmbbrraanneess



Alternative 5-B: Screen Filters + UF + RO + UV Disinfection




UUFFMMeemmbbrraanneess




6.5 Multi-Criteria Evaluation

6.5.1 Criteria Development Various depth (conventional, deep-bed, pulsed-bed, fuzzy filter, cloth filter) and membrane (MF, UF, NF, RO, ED) filtration techniques may be suitable to produce recycled water. For this analysis, four important criteria strongly influenced the selection of the tertiary treatment technologies that were considered. These are:

1. The ultimate water quality desired for the recycled water dictates the level of treatment needed to reach the ultimate quality goal. For example, if recycled water with high purity is of interest, a high level of treatment that requires a combination of treatment steps is needed (such as conventional filtration with chemical addition followed by RO, or MF followed by RO). On the other hand, if recycled water is to be used without contact to edible products, this secondary recycled water may require a low level of treatment (e.g., conventional filtration without disinfection).

2. The quality of source water for tertiary treatment can affect process selection. For example, while secondary effluent of a membrane bioreactor (MBR) system is directly applicable to an RO unit for further treatment, a conventional activated sludge effluent requires pretreatment prior to RO.

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3. The quantity of water that will be treated and phasing requirements have direct impacts on plant sizing, as do capital and operational-maintenance costs.

4. Waste quality and the need for treatment and/or disposal of the waste streams from the advanced treatment process affects treatment selection.

As indicative from the treatment alternatives listed earlier, more than one technology can be selected to meet the desired degree of treatment. However, the selection of the best technology requires a multi-criteria analysis. The assumptions and criteria for this evaluation are presented in the next section.

6.5.2 Selected Criteria Descriptions and Summary Table A multi-criteria decision process in a general sense involves choosing one of a number of alternatives based on how well those alternatives rate against a chosen set of criteria. One such analysis was conducted using the Criterium Decision Plus® software. This software allows use of “Simple Multi-Attribute Rating Technique” (SMART), where each alternative is rated directly, within the predefined scales of the criteria, and the decision model is independent of the alternatives. The advantage of constructing the decision model this way is that the ratings of alternatives are not relative, and changing the number of alternatives considered will not change the decision scores of the original alternatives.

The decision matrix developed for this analysis is presented in detail in Appendix G. The matrix consists of primary criteria that are recommended to be considered in the evaluation of the advanced treatment alternatives for the BBARWA WWTP. Sub-criteria that define each primary criterion in depth also are listed in Appendix G. The set of primary and sub-criteria listed there include:

• Water quality and treatment − Ability to meet changing recycled water quality requirements − Acceptance by CDHS and the Santa Ana Regional Board − Ability to achieve quality goals for groundwater replenishment − Ability to meet quality goals for different uses simultaneously

• Environmental considerations − Noise − Visual Impacts/aesthetics − Traffic impacts − Footprint and land requirements

• Operational considerations − Operational difficulty − Need for chemical use − Process automation − Energy usage − Public safety − Disposal of residuals

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• Flexibility − Ability to construct facilities to match funding − Modularity − Implementation time

• Financial considerations − Capital costs − Annual operations and maintenance (O&M) costs − Cost to users

• Community benefits − Recreational value − Public perception of health and safety of recycled water

• Institutional constraints − Inter-agency agreements − Agency willingness to upgrade WWTP − Permitting

After each criterion was set, it was assigned a weight from a scale that ranged between 0 (trivial) to 100 (critical), depending on the significance in this specific decision-making process. Then a score was assigned for each treatment alternative sub-criterion. These scores ranged from 1 to 5. Treatment alternative scoring was based on the following values:

1 – Not Efficient

2 – Not Significantly Efficient

3 – Moderately Efficient

4 – Efficient

5 – Very Efficient

6.5.3 Assessment and Results The multi-criteria evaluation results obtained from the Criterion Decision Plus® program are summarized in Figure 6-19. The advanced treatment Alternative 4B (MF+RO+UV, Figure 6-16) and Alternative 5B (UF+RO+UV, Figure 6-18) had the highest ranking among the 10 alternatives evaluated. These two alternatives each had a total score of 0.68, and each included membrane filtration followed by UV disinfection.

The next highest ranking alternatives were Alternative 4A (MF+RO+Chemical Disinfection, Figure 6-15) and Alternative 5A (UF+RO+Chemical Disinfection, Figure 6-17), both of which included chemical disinfection. Due to potential complications associated with chemical use, these alternatives scored lower with a total of 0.60.

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B BARWA Ad v an c ed T reatm en t A ltern ativ es Evalu atio n

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

Alt 1A Alt 1B Alt 2A Alt 2B Alt 3A Alt 3B Alt 4A Alt 4B Alt 5A Alt 5B

Mul

ti C

rite

ria R

anki

ng S

core

s

Visual Impacts/Aesthetics

Noise

Footpr int and Land Requirements

Ability to Meet Changing Quality R eqs.

Annual O&M Costs

Ability to Construct Facilities to Match Funding

Ability to Achieve GWR Quality Goals

Agency Willingness to Implement

Acceptance by DHS and RWQCB

Permitting

Recreational Value

Process Automation

Ease of Operation

Need for Chemical U se

Implementation Time

Disposal of Residuals

Staged Implementation

Energy Usage

Inter-Agency Agreements

Ability to Meet Quality for Different U ses

Public Perception

Capital Costs

Public Safety (Potential for Chemical Spills, etc.

Cost to Users

FIGURE 6-19. DECISIONPLUS® MULTI-CRITERIA EVALUATION RESULTS SUMMARY

The alternatives that included a more complicated and multistep treatment approach ranked low mainly due to large footprint, high chemical use, complexity of operation, higher risk for chemical spill, and difficulty of automation. These alternatives also ranked lower due to their limited ability to meet future changes in regulations, especially regulations that could result in stricter limits for emerging pollutants of concern. These pollutants include large organic compounds that can be removed in a barrier system such as NF and RO membranes, but may not be removed effectively through use of chemical precipitation or GAC.

Other factors that had significant impact on final scores were the estimated cost to the users and the suitability for staged implementation (i.e., modularity). The scores were affected negatively for the alternatives that had low scores for modularity (e.g., Alternatives 1-A, 1-B, 2-A, and 2-B).

6.6 Recommended Treatment Approach Based on the multi-criteria evaluation results, Alternatives 4-B (MF+RO+UV) and 5-B (UF+RO+UV) were the preferred alternatives selected for further evaluation. Both of these alternatives include membrane systems (instead of conventional chemical precipitation) and filtration technologies followed by UV disinfection. UV disinfection technology has several benefits, including the flexibility to comply with existing and future regulatory requirements. For example, existing GWR and federal drinking standards strictly regulate disinfection by-products that are formed when chlorine-containing compounds (such as those used in chlorine disinfection) react with organic compounds. While UV disinfection

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provides some degree of microbiological inactivation, it does not form disinfection by-products. CDHS has established health-based advisory levels, called “notification levels” (referred to as “action levels" through 2004), since the early 1980s. These levels have been used to provide information about certain chemicals in drinking water that are nonregulated (i.e., these chemicals lack MCLs).

When chemicals are found at concentrations greater than the notification levels, certain requirements and recommendations apply. CDHS has recommended monitoring of several nonregulated chemicals (such as 1,4 dioxane; n-nitrosodimethylamine; carbon disulfide; and formaldehyde). Monitoring also is recommended for the following endocrine disrupters: ethinyl estradiol; 17-B estradiol; estrone, bisphenol A; nonylphenol and nonylphenol polyethoxylate; octylphenol; octylphenol polyethoxylate; polybrominated diphenyl ethers; acetaminophen; amoxicillin; azithromycin; caffeine; carbamazepine; ciprofloxacin; ethylenediamine tetra-acetic acid; gemfibrozil; ibuprofen; iodinated contrast media; lipitor; methadone; morphine; salicylic acid; and triclosan.

Currently, monitoring such compounds is not for compliance purposes but for informative purposes only. Monitoring for these chemicals is a way of assessing and verifying the quality characteristics of recycled water, which can be useful in addressing issues of public perception about the safety of recharge projects. Some or all of these contaminants quite likely will be regulated (either at action levels or primary MCL levels) in the near future.

An advanced oxidation process (AOP), where a strong oxidant (either hydrogen peroxide or ozone) is used to form hydroxyl radical (OH) when peroxide or ozone is exposed to UV light, is a proven and approved method to reduce a variety of organic materials, including those unregulated chemicals listed above.2 In addition, the maximum average RWC was targeted to be 0.50 for GRRP. However, an RWC of greater than 0.50 requires advanced oxidation treatment subsequent to any RO membrane treatment provided to achieve at least a 1.2-log reduction of n-nitrosodimethylamine and at least a 0.5-log reduction of 1-4 dioxane. Therefore, it is recommended that the UV design include AOP. The design should consider provisions to operate the UV system either in disinfection or in AOP to comply with existing and future regulatory requirements, and when the RWC of greater than 0.5 is desired for GRRP.

6.6.1 Technology Alternatives For the two recommended alternatives, there are numerous membrane equipment vendors, each of which needs to be considered separately, because the materials and design details vary from one to the other. UV disinfection manufacturers also have different design parameters and sizing requirements for their equipment. Pilot testing of the membrane and the UV systems should be conducted prior to the actual design of the treatment units.

Table 6-9 summarizes the typical operational information for the membrane types that are part of the two treatment alternatives.

2 Advanced oxidation pilot study showed that AOP was effective technology in reducing variety of unregulated chemicals, EPA priority pollutants, and pharmaceuticals to nondetectable levels.

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TABLE 6-9 TYPICAL OPERATION CONDITIONS OF MEMBRANE PROCESSES

Membrane Technology

Operating Pore Size, nm

Typical Operating Range, µm

Operating Pressure kPa

Rate of Flux gal/ft2d

Microfiltration >50 0.08-2.0 7-100 10-50

Ultrafiltration 2-50 0.01-0.05 70-700 10-35

Reverse Osmosis <2 0.0001-0.001 850-7,000 8-16

MF and UF systems available from various vendors can be divided into two categories:

1. Submerged Membranes (e.g., Zenon-Zeewed, US Filter-Memcor CMF-S) 2. Pressurized Membranes (e.g., Pall, Koch, US Filter-Memcor CMF )

Table 6-10 summarizes an evaluation of the MF and UF membrane alternatives available from different manufacturers. Table 6-9 also summarizes the characteristics and operating modes for each membrane.

Table 6-11 summarizes an evaluation of the RO membrane alternatives available from different manufacturers. The table includes the full-scale experience and CH2M HILL experience with each membrane type.

Three major UV technology alternatives are available from different manufacturers: Wedeco, Trojan, and Aquionics. All three systems come in different pressure and UV intensity and have applications in water and wastewater.

Table 6-10 Available Microfiltration and Ultrafiltration Membranes

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TABLE 6-11 AVAILABLE REVERSE OSMOSIS MEMBRANES

6.6.2 Treatment Schematics A recommended process schematic for the advanced treatment facility is presented in Figure 6-20. This schematic includes addition of screen filters, MF/UF filtration, RO membrane, and UV disinfection. The schematic also provides other necessary treatment components including pumps, break tanks, and chemical feed points.

Accordingly, secondary effluent from the BBARWA WWTP will pass through screen filters, or “microscreens,” to eliminate residual suspended solids and minimize membrane fouling due to solids deposition. Metcalf and Eddy (2003) defines A microscreen is defined in one source as having openings less than 0.5-µm (Metcalf and Eddy, 2003). However, Water Environment Research Foundation (WERF) defines microscreens as those with openings of less than 100 µm (WERF, 2002). The same WERF report provides an extensive evaluation of various units supplied by different manufacturers, such as Andritz, Hycor, Jones and Attwood, and Pro-Equipment. The suspended solids removals range from 10 to 80 percent depending on the feed quality, the screen opening and backwash frequency, with an average of 55 percent. The screenings can be returned to the main plant headworks or be disposed separately.

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FIGURE 6-20. PROCESS SCHEMATIC FOR THE BBARWA PROPOSED ADVANCED WATER TREATMENT FACILITY

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Microfiltration or ultrafiltration units will follow the screen filters. The membrane reject flow from these units can be returned to the main plant. The feed to the MF/UF units can be chlorinated to limit biological growth taking place on the membranes (i.e., to minimize or prevent biofouling). The chlorine dose must be selected based on the membrane type because different membranes have different tolerance levels for chlorine. The MF/UF permeates then will be collected in a break tank that is included for storage purposes. The tank also will serve as a “break” in the treatment train, from where product water can be pumped to some users of recycled water, after chlorination for pathogen removal. The membrane reject (i.e., filtrate) can be returned to the headworks of the plant for treatment.

Reverse osmosis units will receive water pumped from the break tank after addition of appropriate antiscalants and pH adjustment, predetermined in detail depending on the water composition. The membrane reject from the RO units will need to be further treated or disposed. This stream will be different from the MF/UF reject and will contain various organic compounds, metals, and inorganic constituents. The recommended treatment alternative for the first few phases is to dispose of the effluent into evaporation ponds. To minimize the effect of the advanced treatment effluent infiltrating into surface soils and groundwater aquifers, liners are used in the evaporation ponds.

Many different types of liners are designed specifically for evaporation ponds. Materials used for these liners can range from polypropylene, elvaloys, polyvinyl chloride (PVC), clay material, and the most popular material—high-density polyethylene (HDPE) (Maddocks and Associates, 2005). With these pond liners, infiltration through the underlying soil matrix and into the groundwater is held at a minimum.

The RO permeate may need to pass through a pH adjustment or recarbonation step prior to pathogen reduction via UV disinfection. Hydrogen peroxide (H2O2) can be added before the stream reaches the UV unit to achieve advanced oxidation (AOX). This may be necessary in the future depending on the regulatory changes and product water quality. Final product water will be stored in storage tanks before to pumping to groundwater replenishment site(s).

Figure 6-21 shows the recommended advanced treatment units located on the BBARWA WWTP site. The facilities proposed on this map are located within the existing BBARWA-owned property.

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Figure 6-21 - Treatment Plant Layout for the BBARWA Proposed Advanced Water Treatment Facility±

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19 - Brine Handling Facility

18 - Ultimate RO Facility

20 - UV Facility

21 - Chemical Storage Facility

Staging Area

22 - Storage Tank

23 - Evaporation Pond / Wetlands

13 - Carbon Odor Scrubber

14 - 600 KW Natural Gas Generator

16 - Auxiliary Effluent Pump Station

15 - 550 KW Generator

7 - Main Effluent Pump Station

8 - Sand Drying Bed

9 - Dissolved Air Flotation Thickener (DAFT)

11 - Asphalt Drying Bed

10 - Belt Filter Press (BFP)

12 - Truck Loading

1 - Bar Screens

3 - Oxidation Ditch

4 - Secondary Clarifier

5 - Holding Pond ("Horseshoe Ponds")

6 - Emergency Storage Pond

2 - Aerated Grit Chamber

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Documents

6.1 Project Parameter D R A F T Water Quality Requirements 6 Treatment... · D R A F T D R A F T D R A F T DRAFT REPORT REVISED SEPTEMBER 2005 6-1 6.0 Treatment Alternatives 6.1 Project