Economic Analysis

Graph 1-3 and Table 2: To help understand the size and cost of the plant a basic economic analysis and costing was done. A major find was that for Valrico AWWTF the roughly 60% of the energy cost is in the Oxidation Ditch, where extended aeration takes place.

Environmental Impact AnalysisConsidering Valrico AWWTF is a public utility, the safety standards

they have to meet are stricter, as a large population of Hillsborough County can be negatively affected. As such the facility operated at only half of its actual capacity at all times. Harmful wastewater components are being removed to EPA’s strict restrictions and verified by constant monitoring.

Secondary units are available if the primary fails and a lined reject pond is present for additions influent wastewater the plant cannot handle. As the plant expands, the effect of the increase in discharge should be studied on the local ecosystems.

Recommendations Have mass balances performed around each unit to compare with

model; adjust model to reflect data as accurately as possible. Test controls on the model to see the effects on the process and

feasibility. Insert flow meters to measure flows on return activated sludge and

recycled streams.

Acknowledgements We would like to thank Dr. Aydin Sunol, Kyle Cogswell, Aaron Driscoll, Leslie Knapp, and the Chemical Engineering Faculty and Staff at USF for their continued support and knowledge.

Design of a Municipal Wastewater Treatment FacilityOperation and Quality Control at Valrico Advanced Wastewater Treatment Facility

Dew Rite Wastewater Consultant, LLC: Sasitorn Manning, Jennifer Maynard, Maria MicalUnder the Instruction Dr. Aydin Sunol

College of Chemical and Biomedical Engineering

Model Process Flow Diagram of Valrico AWWTF

Design DiscussionControls implemented on the model have positive results on the process efficiency. Control suggestions include

the following: Set Clarifiers on a time cycle for fill, settle, and drain to maximized mixed liquor volatile suspended solids

(MLVSS) recycled to mix with the primary sludge. Control Clarifier underflow based on primary sludge influent carbonaceous biochemical oxygen demand (cBOD)

concentration Use Oxidation Ditches as anaerobic extension by phasing the ditch for low and high aeration to maximize

ammonia, nitrate, and nitrite conversion per pass

ObjectiveWastewater treatment facilities are continuously upgrading and

improving equipment and technology to meet strict discharge requirements to comply with environmental safety regulations while trying to conserve water.

Valrico Advanced Wastewater Treatment Facility(AWWTF), operating in Hillsborough County, FL, was built in 1990s and is currently seeking Dew Rite Consultants to evaluate and consider process controls for operation. Presented here are several automated control schemes as well as points of interest that the Facility could upgrade to help them better control their processes.

EPA Discharge Requirements

Table 1 presents the compositions in reclaimed water that Valrico AWWTF has to maintain to retain their permit. Maintaining these parameters is the basis of our control proposals.

Points for Process Optimization

BioWin ModelingMany critical assumptions and design constraints were

implemented to help model Valrico AWWTF. BioWin was used to model the plant using an Activated Sludge Digestion Model.

Figure 1: BioWin model made combines similar units in size for simplification.

Installing flow meters on RAS and return from oxidation ditches and influent to clarifiers

Measuring Dissolved Oxygen (DO) in oxidation ditch

Seting Clarifiers on cycle to maintain semi-constant MLVSS concentrations

Scheduling aeration of oxidation ditch by phasing or monitoring DO levels

Economic ParametersPlant Life 20 yearsConstruction Period 2 yearsFCI $39 MWC $3.9 MNPW $20MDCFRR 29.6 %

Parameter UnitsMax/ Min

Annual Average

Monthly Average

Single Sample

Carbonaceous BOD, 5 day-20oC MG/L Max 5.0 6.25 10.0Total Suspended Solids MG/L Max 5.0 6.25 10.0Total Nitrogen (as N) MG/L Max 3.0 3.75 6.0Total Phosphorous (as P) MG/L Max 1.0 1.25 2.0pH SU Range - - 6.0-8.5Fecal Coliform #/100ML Max - - 25Dissolved Oxygen (DO) MG/L Min - - 5.0Dichlorobromomethane μG/L Max 22 -

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

-30-20-10

010203040

Annual Cash Flow for 6 MGD Capac-ity

Time(year)

CF(m

illio

n do

laar

s)

Aeration $400k60%

Wastewater Pumping $79k

12%

Lighting and Buildings $39k

6%

Anaerobic Digestion

$72k11%

Belt Press $19k3%

Clarifiers $19k3%

Other $33k5%

Typical Extended Aeration Wastewater System Energy Consumption

Figures 2-6:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

$(60.00) $(40.00) $(20.00)

$- $20.00 $40.00 $60.00 $80.00

$100.00 $120.00

Cumulative Discounted Cash FlowOptimistic

Base

Pessimistic

Time(year)

CDCF

(mill

ion

dolla

rs)