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Ward Off Wastewater
Woes
Wastewater eHANDBOOK
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TABLE OF CONTENTSUnderstand Industrial Wastewater Treatment 7A variety of techniques play roles in removing contamination
Adroitly Address Wastewater Challenges 14Focus on six key compliance and water consumption issues
Measurement Methods for Chemicals Inventory Abound 22Illinois facility finds success with radar sensor technology
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Additional Resources 33
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 3
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Process plants generally try to min-
imize the amount of wastewater
they generate. However, operations
invariably result in production of some
wastewater. Proper treatment of this waste-
water is crucial for both environmental and
economic reasons.
Industrial wastewaters usually contain
organic and inorganic matter in varying
degrees of concentration. They may include
toxic and other harmful materials as well as
components that are non-biodegradable
or that can reduce the efficiency of many
wastewater-treatment operations.
Thus, treatment of industrial wastewaters
typically is a very difficult task — far more
complicated than municipal wastewater
treatment — that requires special methods
and sophisticated technologies. These
options fall into three categories: physical,
chemical and biological. Physical treatment
methods include sedimentation, flotation,
filtering, stripping, ion exchange, adsorption
and other processes that remove dissolved
and non-dissolved substances without nec-
essarily changing their chemical structures.
Chemical methods include chemical pre-
cipitation, chemical oxidation or reduction,
formation of an insoluble gas followed by
stripping, and other chemical reactions
that involve exchanging or sharing elec-
trons between atoms. Biological methods
rely upon living organisms using organic
or, in some instances, inorganic substances
for food.
Biological treatment is more widely used
than any other option where reasonably
Understand Industrial Wastewater TreatmentA variety of techniques play roles in removing contamination
By Amin Almasi, mechanical consultant
Wastewater eHANDBOOK: Ward Off Wastewater Woes 7
www.ChemicalProcessing.com
complete treatment is required. It most
often serves as the secondary treatment
stage to remove major portions of contami-
nation. Other processes handle primary and
tertiary treatment to complete the removal
of solids and other pollutants.
THE CHALLENGESome industrial wastewaters are rich in
organics and easily biodegradable while
others are nutrient deficient, inhibiting or
preventing biodegradability. Total dissolved
solids and contamination may exceed by
many times the levels found in domestic
sewage. Industrial wastewaters often also
have pHs well beyond the range of 6–9 and
may contain high concentrations of dis-
solved metal salts. To further complicate
matters, wastewater flows and charac-
teristics within a plant also can vary with
time because of campaign manufacturing
or slug discharges on top of the usual dis-
charges. In addition, spillages and dumping
that occasionally may occur very adversely
can impact the performance of the plant’s
wastewater treatment plant. Consequently,
it’s always prudent to carefully assess
current wastewater and its treatment
requirements rather than relying on the past
situation. An understanding of the nature of
the plant’s operations is vital.
One key parameter for wastewater is its
biochemical (or biological) oxygen demand
(BOD). This is the amount of dissolved
oxygen needed by aerobic biological
organisms to break down organic mate-
rial present in a given wastewater sample
at a certain temperature over a specific
time period. Therefore, BOD indicates indi-
rectly the amount of organic compounds
in wastewater. The BOD most commonly
is expressed in milligrams of oxygen con-
sumed per liter of sample during 5 days of
incubation at 20°C.
Another key parameter is chemical oxygen
demand (COD), which indirectly specifies
the amount of organic compounds in the
wastewater. It indicates oxygen consump-
tion and also is given in mg/L.
Both BOD and COD measure the amount
of organic compounds in wastewater.
However, COD is less specific because it
measures everything that can be chemically
oxidized rather than just levels of biode-
gradable organic matter. You can estimate
the biodegradability of wastewater by con-
sidering its COD and corresponding BOD.
PRIMARY TREATMENTRemoving large, suspended and float-
ing solids is the focus of the first stage of
wastewater treatment. However, before
such treatment takes place, the plant
wastewaters usually first go to an equaliza-
tion tank or system, which acts as a buffer
and normalizes varying flow and contami-
nation loads. It’s always best to use a single
large concrete tank to which an appro-
priate coating has been applied. This tank
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 8
most often is sized based on the difference
between expected peak and average flows,
with a capacity of 4–8 hours’ worth of dif-
ference common.
From the equalization tank, the raw
wastewater goes for primary treatment.
This usually includes screening to trap
solid objects, sedimentation by gravity
to remove suspended solids and some
adjustments. Primary treatment sometimes
is referred to as “mechanical treatment”
because it relies on mechanical meth-
ods, although chemicals often are used
to accelerate the sedimentation process.
The design for a primary treatment facility
most often includes neutralization (i.e., pH
adjustment), coagulation, flocculation and
dissolved air flotation (DAF).
The main purpose of primary treatment is
to remove colloidal solids, emulsified oil and
a small portion of BOD and COD. Primary
treatment can reduce BOD of the incom-
ing industrial wastewater by around 20–30
% and the total suspended solids by some
50–65%.
Neutralization. Usually, wastewater must
have its pH adjusted so that subsequent
operations such as downstream biological
treatment can take place at optimum pH.
Therefore, the wastewater passes to a neu-
tralization system that corrects its pH. This
system generally involves multiple neutral-
ization tanks; common configurations are
“3+1” (3 operating + 1 standby), “5+1” (5
operating + 1 standby) and “7+1” (7 operat-
ing + 1 standby). Injection of chemicals such
as a caustic soda or sulfuric acid solution
adjusts the pH to the desired level.
Sensors installed at the inlet and outlet of
the neutralization tank (a minimum of one
sensor in each location) measure the pH
of the wastewater. A controller uses these
readings to automatically adjust a dosing
pump to achieve the desired final pH (typi-
cally, 6.7–8.3 with an optimum of 6.9–7.4).
The neutralization-chemical system con-
sists of storage and mixing tanks and other
equipment such as agitators necessary to
reduce the concentration of the chemical
and prepare it for injection. Dosing pumps
are deployed in a “1+1” arrangement (1 oper-
ating + 1 standby) for each chemical. Often
positive displacement pumps handle these
services. However, these sometimes can
pose maintenance and reliability issues. A
variable-speed-drive centrifugal pump often
offers an attractive alternative that provides
reliability and high performance.
Coagulation and flocculation. Wastewater
from the neutralization tank usually flows by
gravity into coagulation tanks for removal
of colloidal solids. Coagulation is a quick
process, requiring a relatively low retention
time of 2–5 min. There commonly are mul-
tiple rectangular coagulation tanks made
of reinforced concrete with proper coating;
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 9
each contains a few agitators that provide
high-energy mixing. Large plants often use
configurations such as “7+1” (7 operating + 1
standby) or “9+1” (9 operating + 1 standby)
or similar. For instance, a treatment plant of
3,000-m3/hr total capacity employed “7+1”
tanks, each of 16 m3 capacity, to achieve
retention time of more than 2.2 minutes.
Some large plants have used retention
times as low as 1.5 min and certain radical
designs propose times as low as 1 min. How-
ever, low retention times can pose risks.
Generally, it’s wise to keep retention times
above 2 min.
A coagulant solution (typically polymer
based) usually is injected automatically
by dosing pumps (“1+1” configuration);
most often stroke variation adjusts injec-
tion. Modern plants automatically control
injection rate according to incoming
flow rate based on a more or less fixed
chemical concentration, preliminarily
defined through site experimental tests
and adjustable during normal plant oper-
ation. Coagulant aid can be added to the
wastewater stream to facilitate separation
of solids.
Wastewater from coagulation tanks most
often flows by gravity into the floccula-
tion system (tanks) where agglomeration
of flocculent formed during coagulation
process takes place. Anionic polymer usu-
ally serves as flocculent. Flocculation is
a process of slow mixing with retention
times of 12–40 min. Some designs for large
plants have used lower retention times,
say, 9–10 minutes, but typically times of 11,
12 or 15 min. are recommended. It is a pro-
cess that requires less energy for agitation
than coagulation.
Dissolved air flotation. Wastewater from
flocculation passes by gravity into a DAF
clarifier system. Its main purpose is to
remove the suspended solids, emulsified
oil, grease and some portions of BOD and
COD from the wastewater. Elimination
occurs through the action of micron-sized
air bubbles. These are created by dissolv-
ing air in wastewater under pressure and
then reverting to atmospheric pressure in
DAF clarifiers. The millions of micron-size
air bubbles released attach to the contam-
inants, decreasing their effective density
and thus causing them to float on the sur-
face to form a concentrated sludge blanket.
A skimming device removes the floating
sludge, which then go to sludge treatment
units for processing. A common design uses
a separate pressure vessel for compressed
air introduction. DAF clarifiers operate
effectively over a wide range of hydraulic
and contamination loading.
SECONDARY TREATMENTOften considered the heart of the treatment
plant, its major purpose is to remove biode-
gradable organics (expressed as BOD, COD,
etc.) and ammonia. Secondary (or biolog-
ical) treatment uses microbes to consume
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 10
dissolved organic matter that escapes pri-
mary treatment, converting it to carbon
dioxide, water and energy for microbe
growth and reproduction. After this biolog-
ical process, the stream goes to additional
settling tanks (“secondary” clarifiers or sed-
imentation vessels) to eliminate more of the
suspended solids. Well designed and func-
tioning secondary treatment can remove
about 85–90% of the suspended solids and
BOD. Technologies employed include the
activated sludge process, which is the most
commonly used method, as well as variants
of pond and constructed wetland systems,
trickling filters and other forms of treatment
that rely on biological activity to break
down organic matter.
An activated-sludge train usually is divided
into an aeration section for BOD removal
and nitrification, and an anoxic section for
denitrification. In the aeration section, com-
pressed air passes through the wastewater.
Dissolved oxygen from the compressed
air acts as a respiratory source for aerobic
bacteria present in wastewater that decom-
pose the organic load (expressed as BOD
and COD) and ammonia to carbon dioxide
and nitrates, respectively. In the anoxic sec-
tion, bacteria use the oxygen in nitrates as
a respiratory source, thus converting the
nitrates to nitrogen gas.
In practice, denitrified wastewater from
the anoxic tank flows downstream to the
aeration (or BOD-removal) tank where
aerobic bacteria decompose the organic
load and ammonia present using dissolved
oxygen supplied by air blower(s). The
treated effluent from the aeration tank
usually flows by gravity to a secondary
clarifier, which most often is a gravity
clarifier. Here, sludge is removed from
the treated effluent, which then passes
to tertiary treatment. A portion of the
sludge gets recycled to the anoxic sec-
tion to provide nitrates for denitrification.
This recirculation keeps effluent nitrates’
concentration below the required limits.
The remaining portion of sludge goes to
sludge treatment facilities.
Biological treatment usually consists of
multiple streams, say, 4, 6 or 8 trains, with
a proper safety factor (for instance, 1.5 or
more) to ensure the biological treatment can
handle the incoming design flow even if one
train is taken out of operation. Selection of
the hydraulic retention time for the anoxic
zone requires great care. Considering dif-
ferent operational and process factors, as
a rough indication, this time usually is 5–8
hr. Some designs for large plants have used
5.5 hr, 6 hr and 6.5 hr as optimum values.
Hydraulic retention time for the aeration
Selection of the hydraulic retention time for the anoxic zone requires great care.
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 11
tank is longer, somewhere between 19 and
24 hr. Some large plants have found a reten-
tion time of 20 hr to be optimum.
TERTIARY TREATMENTThis ensures removal of remaining contam-
ination and solids in the wastewater. Such
tertiary treatment usually involves filtration
systems such as disc filters, reverse osmosis
(RO) units (Figure 1), etc. You usually should
direct filter reject from backwash or RO
unit rejects to the flow distribution cham-
ber upstream of the equalization system;
most often, these rejects require a dedicated
pumping system. To eliminate specific con-
taminations to meet regulatory requirements,
many plants must resort to special treatment,
e.g., the Fenton process to remove non-bio-
degradable COD. While other technology
options are available, the Fenton process
most often is selected because of its reliabil-
ity, initial cost, operational cost and footprint.
The Fenton section usually consists of
dosing systems for hydrogen peroxide
and ferrous sulfate. After dosing with
chemical in an oxidation tank, the waste-
water goes to tube settlers to settle out
the contaminants. During regular oper-
ation plants generally don’t need to put
wastewater through such treatment. How-
ever, having a Fenton section can ensure
treatment adequacy when facing sus-
tained peak COD in the wastewater.
Many units in tertiary treatment such as
that for the Fenton process or fine filtra-
tion should consist of multiple parallel
streams to provide flexibility during oper-
ation. Commonly used arrangements are
“n+1” and “n+2” — for example, “2+2” “3+1”
“4+2” and “5+1”.
AMIN ALMASI is a mechanical consultant based in
Sydney, Australia. Email him at [email protected].
REVERSE OSMOSIS
Figure 1. Use of such a unit for tertiary
treatment of wastewater is
becoming popular.
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 12
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Wastewater management is one
of the most challenging oper-
ational issues facing chemical,
petrochemical and other process plants
today. Three primary factors contribute to
this: wastewater compliance standards are
growing increasingly strict, water consump-
tion costs are rising, and a water shortage is
looming in many areas.
The U.S. Environmental Protection Agency
(EPA) assessed a staggering $69 million in
pollution penalties in 2018 alone. Meanwhile,
the cost of water is getting higher through-
out the United States. In addition, more
and more processors are treating effective
and efficient processing of fluid byprod-
ucts as much as a corporate sustainability
imperative as an environmental responsibil-
ity. This is a pressing issue for all chemical
processing operations but smaller facilities
may feel improved wastewater manage-
ment is out of reach because they lack
in-house compliance expertise or advanced
wastewater-treatment technologies. What’s
more, understanding a facility’s wastewa-
ter compliance obligations can be difficult
because dense regulatory terminology per-
meate wastewater standards and mandates
may depend upon the particular local pub-
licly owned treatment works (POTW).
Chemical processors that take steps to
better understand wastewater regula-
tions and deploy advanced technologies
to reduce recurring costs associated with
wastewater compliance will position them-
selves for a stronger future. Here are six
areas to focus on to take control of waste-
water compliance.
Adroitly Address Wastewater ChallengesFocus on six key compliance and water consumption issues
By Tim Hanna, PRAB
Wastewater eHANDBOOK: Ward Off Wastewater Woes 14
www.ChemicalProcessing.com
1. CRITERIA BEHIND REGULATIONS Wastewater discharge regulations include
a fair amount of complexity. Lack of a
high-level understanding of their frame-
work and enforcement can pose a real
barrier to effective and efficient compli-
ance management.
Since 1972, the United States has pursued an
increasingly stringent water control program.
From the EPA’s perspective, two kinds of
wastewater discharges need to be regulated
under the Clean Water Act (CWA): direct
discharges into “waters of the United States”
and indirect discharges that pass through a
POTW for treatment prior to being released
into the water supply.
Indirect discharges are regulated through
a national pretreatment program that is
a cooperative effort of federal, state and
local environmental regulatory agencies.
The objective of the program is to pro-
tect POTWs’ infrastructure and reduce the
amount of industrially generated pollutants
discharged into the municipal sewer system
and the environment.
The EPA has established three primary
kinds of pretreatment standards:
• general and specific prohibited discharge
standards for all industrial users;
• categorical pretreatment standards for
particular industrial categories, including
inorganic chemicals, ink formulating, oil
and gas extraction, organic chemicals,
plastics and synthetic fibers, paint for-
mulating, pesticide chemicals, petroleum
refining, pharmaceutical manufacturing,
rubber manufacturing, and soap and
detergent manufacturing; and
• local limits that are site-specific to ensure
the POTW will not process waste that
passes through to the water supply or
interferes with operations.
Standards outside of the CWA also factor into
wastewater compliance. Under the Resource
Conservation and Recovery Act (RCRA), the
EPA regulates the transport, treatment, stor-
age and disposal of solid waste (including oils
and sludges). While not a direct component
of discharge regulations, U.S. Occupational
Safety and Health Administration (OSHA)
standards also impact a chemical processor’s
approach to wastewater management. Toxic
and other hazardous gases can arise when
certain inorganic pollutants in wastewater mix
in the discharge collection system. OSHA sets
exposure limits on toxic and air contaminants
to protect worker health. POTWs will reduce
this risk by controlling the maximum level of
pollutants discharged.
Tip: When it comes to understanding the
scope of wastewater requirements for a
plant — and optimizing solutions to manage
wastewater treatment — operators must
appreciate that air discharge limits also play
a role. For example, a wastewater treatment
system requires proper ventilation. If a wet
scrubber removes toxic substances from
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 15
gases, the toxic substances will collect in
the wastewater generated by the scrubber,
creating an additional wastewater stream to
manage.
2. THE PURPOSES OF PERMITTINGAt a minimum, the EPA requires all signifi-
cant industrial users (SIUs) to have permits.
The EPA defines SIUs as:
• industrial users (IUs) that fall under cat-
egorical pretreatment standards due to
their industry;
• IUs that discharge an average of 25,000
gal/d or more of process wastewater
(excluding sanitary, noncontact cooling
and boiler blowdown wastewater) to
the POTW;
• IUs that contribute a process waste
stream that makes up 5% or more of the
average dry-weather hydraulic or organic
capacity of the POTW;
• IUs that the control authority identifies as
having a reasonable potential to adversely
affect the POTW’s operation; and
• IUs that have violated any pretreatment
standard or requirement.
The permitting process usually is one of the
clearest illustrations that the onus of pro-
active wastewater compliance falls on the
process plant. Not only can local wastewater
authorities define SIUs in their jurisdiction
more stringently than the federal EPA but
also EPA counsels local wastewater authori-
ties to communicate pretreatment standards
during the permitting process. In “The
Industrial User Permitting Guidance Manual,”
https://bit.ly/3k8fpg1, the EPA states that, in
its experience, “the permit is the most effec-
tive means of ensuring that industrial users
are aware of all applicable pretreatment
requirements.”
Most permit applications require plants
to disclose a broad range of details about
their wastewater management, such as a
description of operations, wastewater gen-
erating and discharge activities, and the
pollutants potentially in the wastewater
and on-site. From the chemical proces-
sor’s perspective, it would seem that the
operator must supply all the details of its
wastewater management practices prior
to learning which discharge regulations
will apply. This approach compromises
the operator’s ability to initiate pollution
abatement practices that may streamline
permit approvals and reduce surcharges
levied by the POTW to cover costs for
treating wastewater with excessive pollu-
tion levels.
Tip: For plants that add an in-house
wastewater treatment system, the permit
application will need to clearly state where
the system will be located within the facility
and the location of the sample port so reg-
ulators can perform testing. Some suppliers
of wastewater treatment technology will
work with plants and wastewater regulators
to submit and obtain the necessary permits
on behalf of the facility.
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 16
3. RECURRING COMPLIANCE COSTS Wastewater compliance can incur many
costs such as treatment expenses, labor
investments, and fines that can erode a
chemical processor’s bottom line.
Wastewater compliance lapses, for example,
can lead to serious financial liability. A facil-
ity negligently or knowingly discharging to a
POTW in violation of federal or local pretreat-
ment standards can face significant penalties:
• negligence violations — initial penalty:
1 year and/or $2,500–$25,000/d, sub-
sequent convictions: 2 years and/or
$50,000/d; and
• knowing violations — initial penalty: 3
years and/or $5,000–$50,000/d, sub-
sequent convictions: 6 years and/or
$100,000/d.
If a discharge introduces a pollutant or haz-
ardous substance into a POTW and the
person knew or reasonably should have
known such pollutant could result in injury or
damage the system, or the discharge causes
the plant to violate its own permit, the penal-
ties are the same as those for a discharge to
a POTW in violation of a local pre-treatment
program.
Chemical processors have two choices if
they are to avoid such compliance fines:
treat wastewater to meet local POTW stan-
dards prior to discharging it to the sewer
or pay to have wastewater hauled away
and treated, which easily can total several
thousand dollars per week. The costs to
transport (either by bulk drums or tank-
ers) and treat wastewater are increasing
and likely will continue trending upward.
According to data from the U.S. Bureau of
Labor Statistics, costs for waste collection
and remediation services rose 12% from
June 2014 to June 2019.
Tip: Facilities that have an in-house waste-
water treatment system and a discharge
permit are not exempt from monitoring
and testing. These plants still must perform
regular visual tests and send samples out
for an official analysis (usually twice a year).
Additionally, failure to pay fees, charges or
surcharges typically are viewed as compli-
ance lapses and also are subject to legal
action.
4. WATER USE COSTS While wastewater compliance is a neces-
sary aspect of chemical manufacturing,
reducing water consumption expenses is a
related component of cost-effective waste-
water management.
According to estimates in 2017 research
from the American Council for an Ener-
gy-Efficient Economy, www.aceee.org,
among all U.S. manufacturing sectors,
chemical making accounted for the third
greatest volume of water withdrawal,
behind only pulp and paper and pri-
mary metals. More important, though,
the chemicals subsector ranked highest
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 17
in consumptive use, followed by primary
metals and petroleum refining.
With water costs rising and water demand
expected to exceed the current supply by
2030, taking steps to reduce water con-
sumption through wastewater recycling and
re-use could dramatically impact chemical
processing facilities for the better.
Tip: Recycling or repurposing washdown
water can cut water consumption substan-
tially. For example, a chemical blender of
industrial metalworking fluids uses as much
as 20% of its incoming water to clean out
the facility’s mixing vats. Treating this water
enables its reuse, markedly reducing incom-
ing water usage.
5. OUTSIDE EXPERTISE Achieving wastewater compliance in a
cost-effective manner requires a balance of
technology and compliance expertise. An
ability to work with local control authorities
to become familiar with applicable regu-
lations and adopt measures to meet the
regulations underpins this.
Unfortunately, chemical companies —
whether new or long-established — can find
pursuing pre-emptive compliance measures
extremely challenging when their primary
information liaison is also the enforcing party.
An experienced, trusted supplier of industrial
wastewater treatment technology will be
familiar with local and federal pre-treatment
standards and, in some cases, can act as an
“information agent.” For example, when a
plant operator poses questions to wastewa-
ter regulatory officials, it may risk inviting
followup requests from the regulator. As a
neutral third party, a wastewater equipment
supplier may be able to answer the questions
itself or consult with regulators without dis-
closing specific details.
Furthermore, wastewater treatment
systems for chemical plants are not
one-size-fits-all. Determining the most
cost-efficient and effective technology for
the specific application requires a thorough
understanding of the wastewater’s makeup
(Figure 1). For example, correctly specifying
and optimizing a reverse osmosis system
demands the following data: pH, total dis-
solved solids, chemical oxygen demand,
biochemical oxygen demand, operating
temperature, chloride, ammonia, oil and
THOROUGH EVALUATIONFigure 1. Selecting the most appropriate treat-ment system requires a detailed and accurate analysis of the wastewater.
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 18
grease, total suspended solids, sulfates,
calcium, magnesium, and emulsified oil and
grease.
Tip: Do not exclusively rely on historical
wastewater data. Carefully evaluate the
current wastewater in the context of the
plant’s current operating parameters, which
are subject to change as production goals
fluctuate. An experienced and trusted sup-
plier of industrial wastewater technology
can evaluate a facility’s wastewater stream
by running tests and obtaining a laboratory
analysis of samples before and after various
treatment options. From those results, the
supplier can recommend the proper equip-
ment and treatment methods to recycle or
repurpose the permeate.
6. ZERO-LIQUID-DISCHARGE TECHNOLOGIES The EPA’s Effluent Guidelines, www.epa.
gov/eg, set technology-based numerical
limitations for specific pollutants on an
industry-by-industry basis, including sev-
eral chemical processing applications. The
guidelines don’t require the use of a specific
technology to achieve reduction.
Several available zero-liquid-discharge
technologies can be installed on-site to
cut water pollution and prepare water for
repurposing within the production facil-
ity. In many instances, a plant may need
to deploy multiple modular technologies
to optimize wastewater treatment and
recycling. Three of the most common
processes for chemical plant wastewater
treatment are ultrafiltration, vacuum evapo-
ration and reverse osmosis.
• Ultrafiltration uses low pressure to push
wastewater through a semipermeable
membrane. The technology filters out
organics, emulsified oils and suspended
solids, reducing oily water volumes by as
much as 98% without chemicals. Ultra-
filtration systems can cut the cost of
washwater and detergents by as much
as 75% and decrease haul-away costs by
90%. Such systems can help manufactur-
ing facilities meet a goal not hauling away
any wastewater and provide them the
ability to meet RCRA requirements and
state and local discharge regulations.
• Vacuum evaporation is one of the most
effective methods for mitigating the
risks and costs associated with chemical
manufacturing wastewater. This process
removes salts, heavy metals and a vari-
ety of hazardous components. It restores
90–95% of the original distillate (water),
cuts the cost of washwater and deter-
gents up to 75%, and reduces water costs
up to 99%. Vacuum evaporation also has a
low carbon footprint.
• Reverse osmosis is a low-maintenance
method that removes dissolved solids by
using high pressure to push wastewater
through a semipermeable membrane.
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 19
The technology removes up to 99.5% of
dissolved salts and impurities. Often this
technology serves as the final process
after ultrafiltration or chemical treatment
of wastewater.
Tip: Partner with a wastewater treatment
system supplier that offers all types of
technology and that will work in lockstep
with plant operators throughout the entire
equipment acquisition — from sampling
and permitting to testing and installation.
Also, be sure to pursue testing and feasi-
bility studies before equipment selection.
Equipment suppliers that collect waste-
water samples from the plant, run those
samples through their proprietary waste-
water treatment systems and then verify
the results of the processing through a
certified laboratory not only have proof of
projected water quality improvements but
also will have collected data required for a
new discharge permit application.
BUOY YOUR BOTTOM LINEWastewater regulations almost will
certainly grow increasingly stringent.
Chemical processors that partner with
wastewater treatment experts to establish
improved compliance practices will bene-
fit from lower discharge fees, labor costs
and haul-away expenses. In addition, by
recycling wastewater to the production
line for use, a plant will lower fresh water
expenses. Chemical manufacturers that
leverage this potential will make waste-
water compliance less of a drain on their
operation.
TIM HANNA is the vice president of business devel-
opment for PRAB, Kalamazoo, Mich. Email him at
REVERSE OSMOSIS UNITFigure 2. This technology can remove up to 99.5% of dissolved salts and impurities, and often serves as the final step in a treatment system.
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 20
The varying compositions of chem-
icals we use today are as diverse
as the manufacturers and the dis-
tributers who ensure a steady supply for
consumers and industry alike. Likewise, the
technology these companies use to mea-
sure and manage their chemical inventories
can be just as diverse.
These facilities have an array of options
for measuring the amount of chemi-
cals they have inside their tanks. A large
chemical manufacturer and distributor
had previously been using weigh scales
installed beneath every tank and vessel at
its facility in Illinois. However, it recently
switched to high-frequency through-
air radar sensors. This article compares
the two technologies and highlights the
their differences.
WEIGH SCALES Weigh scales, sometimes referred to as
load cells, are in wide use for measuring
inventory in large tanks. These scales are
installed under a chemical tank to make
a weight measurement. Using this mea-
surement and a known density, the sensor
electronics can output a volume to help
facilities better manage their inventory.
Weigh scale technology is easy to under-
stand, and it works. A weight measurement
is made mechanically, which can be cal-
culated easily into an accurate volume
measurement using a known density and
a simple formula. Because weigh scales
have no contact with the medium being
measured, these sensors can measure any
liquid chemical despite corrosive or harm-
ful properties.
Measurement Methods for Chemicals Inventory Abound Illinois facility finds success with radar sensor technologyBy Greg Tischler, VEGA Americas
Wastewater eHANDBOOK: Ward Off Wastewater Woes 22
www.ChemicalProcessing.com
The straightforward measurement,
however, is where the simplicity ends.
Installations alone can be costly, time-con-
suming and labor-intensive. Installing a
single system means lifting the entire
vessel and placing the weigh scale under-
neath. Shutting down a process or taking
a vessel out of use, if necessary, increases
costs further.
Weigh scales also are expensive to main-
tain. These instruments make a mechanical
measurement, so they need to be cleaned
regularly, recalibrated and repaired. All of
this takes valuable time for maintenance
crews, and yet, for many facilities, this
process has become routine. Every few
months, vessels are taken out of service so
maintenance crews can inspect and reca-
librate instrumentation. They don’t realize
there’s another way.
HIGH-FREQUENCY RADARThrough-air radar works by emitting
radio microwaves from the radar antenna
system to the measured product where
it is reflected by the product surface and
back to the antenna system. The radar
sensor uses time of flight to measure
product level. Radar sensor electronics
can use the level measurement and the
vessel geometry to calculate product
volume inside the tank.
Real-world benefits of high frequency
80 GHz radar can be seen in an array of
applications, including chemical tanks.
Radar sensors with 80 GHz frequency have
enhanced focusing, the ability to make
measurements through plastic vessels and
special software to generate an accurate
and reliable echo curve to interpret the
level inside the vessel.
A radar beam’s focus is dependent on two
factors: the radar transmitter’s antenna size
and its transmission frequency. A smaller
antenna or a lower frequency results in
a wider, less focused beam. Conversely,
a larger antenna or a higher frequency
results in a narrower, more focused signal.
Therefore, a radar sensor using a high 80
GHz frequency can accurately measure
in small or narrow vessels with little to
no interference.
Radar signals also can also penetrate non-
conductive products such as plastic and
fiberglass. Because many chemicals are
stored in tanks made of polyethylene,
Installation alone can be costly, time-consuming and labor-intensive.
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 23
commonly referred to as poly tanks, an 80
GHz radar sensor can be installed above
these tanks without the need for an addi-
tional process connection (Figure 1). This
simplifies and decreases the costs associ-
ated with installation.
The intelligent electronics within today’s 80
GHz radar sensors multitask to meet indi-
vidual user needs. In its most basic function,
the electronics output a level measurement,
but it also can calculate a volume measure-
ment using known vessel geometries. Those
same electronics even can filter out signal
interference from condensation or dust and
dirt built up on the antenna, eliminating
the need for regular maintenance, cleaning
or recalibrations.
MEASUREMENT TECHNOLOGY UPGRADEThe chemical manufacturer and distribu-
tor in Illinois had grown tired of calibrating
its weigh scales constantly. Tanks at this
facility ranged in size from small, portable
tanks to large vessels capable of holding
thousands of gallons. Over time, measure-
ments would drift, which resulted in slight
measurement errors at best and dangerous,
costly spills at worst. And whenever the
facility needed to move a tank, the weigh
scale sensors would have to be recalibrated
and recertified. The cost of maintaining all
the weigh scales was growing.
After exploring the available measurement
options, operators at the facility chose
RADAR SENSOR ABOVE POLY TANKFigure 1. The radar sensor is mounted above the polypropylene tank, eliminating the need for an additional process connection.
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 24
to purchase an 80 GHz radar sensor with
a fixed cable connection attached to a
chemical-resistant polyvinylidene fluoride
(PVDF) housing. Installation was inexpen-
sive and straightforward. Maintenance
installed some of the radars in existing
process connections on top tanks, while
others simply hung the radar above the
poly tank and measured through the top
of the vessel.
ACCURATE RESULTS WITH LESS MAINTENANCEInstalling these radar sensors resulted in
accurate measurements, which eliminated
inventory errors, overfilling and safety
concerns related to incorrect measure-
ments. The sensors provided accurate
volumetric measurement outputs with-
out the need for ongoing maintenance. A
simple swap of measurement instrumen-
tation improved operational efficiency
and safety records. Now the company is
moving forward with plans to standardize
its measurement instrumentation at facili-
ties across the United States.
GREG TISCHLER is radar and guided wave product
manager at VEGA Americas. He can be reached at
RADAR SENSOR AND DISPLAY INSTRUMENTFigure 2. The VEGAPULS C 11 radar sensor hangs above the chemical tank and provides an accurate level measurement, which is shown on the VEGADIS 81 display instrument next to the vessel.
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 25
Sewage treatment is more than a dirty
job. It is considered a hazardous
work environment by the U.S. Occu-
pational Safety and Health Administration
(OSHA); the U.S. Environmental Protection
Agency (EPA); the National Fire Protection
Association (NFPA); as well as multiple other
local, state and global regulators.
Employees working in wastewater treat-
ment plants from face real dangers,
including exposure to combustible and
toxic gases such as hydrogen sulfide (H2S),
methane (CH4), carbon monoxide (CO) and
others, as well as hazards associated with
oxygen (O2) deficiency in confined spaces.
Pumps stations supporting the primary
phase of the wastewater treatment process
(Figure 1) are a recognized area of concern
for gas safety. Inflows from municipal sewer
lines are directed to large, open-air tanks
before treatment. Fixed gas detector mon-
itoring of dry and wet wells is necessary
to avoid dangerous combustible and toxic
levels of these naturally occurring waste
gases.
As a recognized industry safety standard
with the de facto force of regulation, com-
pliance with NFPA Code 820 Standard for
Fire Protection in Wastewater Treatment
and Collection Facilities is designed to
prevent gas explosions and fires. Other
industry standards that apply include IEC
61508 and 61511, which help ensure the safe,
dependable and reliable design and opera-
tion of combustible gas and flame detection
monitoring equipment and systems across a
range of industrial applications.
Integrated Gas Monitoring Systems Help Meet NFPA Code 820Keep workers and physical assets safe from hazardsBy Tim Wolk, MSA Safety
Wastewater eHANDBOOK: Ward Off Wastewater Woes 27
www.ChemicalProcessing.com
Wet wells are the large, open holding tanks
where municipal wastewater is stored ini-
tially at treatment plants. In these large
tanks, heavier solids sink to the bottom and
lighter materials float to the top for removal
before the remaining wastewater is pumped
to secondary treatment areas. During
this process, mixed levels of combustible
and toxic gases such as methane, hydro-
gen sulfide and other dangerous gases
can be present in varying quantities. Here
the potential for oxygen deprivation also
exists—especially in confined space areas.
The combustible gases and the toxic gases
generally are invisible and can exhibit a
rotten-egg smell (hydrogen sulfide) or
pungent smell (methane), which can be
deceiving in terms of their potentially lethal
nature—in terms of both combustibility and
toxicity. Combustible and toxic gas detec-
tors alert system operators when this gas
cocktail becomes intense enough to rep-
resent a serious fire danger or respiratory
threat to employees.
COMBUSTIBLE GASESCombustible hydrocarbon and toxic gases,
such as methane, are natural by-products
of human and animal waste streams. When
gathered and collected through municipal
sewer systems into large waste streams for
treatment, they become concentrated, often
leading to odor control issues and potentially
hazardous combustible gas levels affecting
worker safety. This can occur during rou-
tine maintenance activities requiring the use
of tools and other common equipment, in
WASTEWATER PUMP STATIONFigure 1. This di-agram portrays a typical wastewater treatment plant and process layout.
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 28
which mixed waste gases are highly com-
bustible under the right conditions at 100%
lower explosive limit (LEL).
HYDROGEN SULFIDEOnce released into the air, H2S gas with its
rotten egg smell can be present for weeks
as an annoying and potentially dangerous
air pollutant. While not technically a green-
house gas, it has been dubbed the “other
greenhouse gas” by some because it tends
to get trapped within the atmosphere.
According to the National Institute for
Occupational Health and Safety (NIOSH),
H2S exposure can cause irritation to the
eyes and respiratory system. At higher
levels, it results in apnea, coma, convulsions,
dizziness, headache, weakness, irritability,
insomnia and stomach upset, leading to
death in the worst cases.
CARBON MONOXIDECarbon monoxide is an odorless, colorless
gas that can cause sudden illness and death.
It is produced any time a fossil fuel is burned,
such as when excess waste gas is flared at
municipal waste treatment facilities or in con-
fined areas where gasoline-powered engines
are present. Exposure to CO impedes the
blood’s ability to carry oxygen to body tis-
sues and vital organs. Common symptoms
are headache, nausea, rapid breathing, weak-
ness, exhaustion, dizziness and confusion.
Severe exposure can result in damage to the
brain or heart—and even death.
OXYGEN DEFICIENCYOxygen-deficient atmospheres are the
leading cause of worker confined-space
fatalities in industrial plants in which
employees must perform routine main-
tenance tasks. While normal atmosphere
contains between 20.8 and 21% oxygen,
OSHA defines as oxygen-deficient any
atmosphere that contains less than 19.5%
oxygen and as oxygen enriched any atmo-
sphere that contains more than 22%.
Oxygen deficiency in municipal wastewater
treatment plants is a real threat to worker
safety with their complex array of large
tanks, vaults, pipes and other equipment.
NFPA CODE 820NFPA Code 820 has been around for
decades and has gone through multiple
iterations to improve its effectiveness. The
scope of this standard is to establish min-
imum requirements for protection against
fire and explosion hazards in wastewater
treatment plants and associated collection
systems, including the hazard classification
of specific areas and processes.
This important safety standard identifies
three separate process areas of concern
relating to combustible gases: (1) collec-
tion areas, (2) liquid streams and (3) solids
treatment. The standard applies to multiple
types of sewers, pumping stations, treat-
ment facilities, sludge handling facilities,
chemical handling facilities, treatment facili-
ties and ancillary structures.
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 29
The requirements for monitoring wet wells
with combustible gas detectors are identi-
fied in Table 5.2: Liquid Stream Treatment
Processes of the standard. Each area requir-
ing combustible gas detection monitoring is
listed in a clear, concise manner for ease of
understanding the application.
SOLUTIONS FOR PUMPING STATIONS AND WET WELLS The MSA TriGas Monitoring System (Figure
2) is an example of an integrated combus-
tible gas monitoring product that helps
plant operators comply with NFPA 820.
The system consists of up to three sen-
sors to alert personnel of gas leak hazards
with on-board alarming and communica-
tion interface to plant and remote location
control stations. Achieving NFPA 820 com-
pliance for pumping stations, lift stations,
influent headworks and wet wells associ-
ated with wastewater treatment plants that
are all subject to flooding is ideal for a gas
monitoring system with sample draw.
The system monitors for combustible
gases (for example, methane or petroleum
vapors), hydrogen sulfide and oxygen) and
offers sampling in high-moisture environ-
ments and poor access areas. Additional
features offer compliance with other
NFPA codes.
The system also is designed to accept sam-
ples from NEC Class I, Div. 2 areas from
wet wells with open channels that have
hazardous classification reduced by the
proper amount of air exchanges required.
OTHER FEATURES TO CONSIDERWhen selecting an integrated combustible
gas monitoring product, consider whether
the unit has additional mounting feet and
handles that allow it to be placed near a
confined-space entrance, alerting workers
as to the confined space’s atmospheric
conditions. This can be used to comply with
OSHA Standard 1910.148 Appendix E Sewer
System Entry guidelines when fixed gas
monitoring is required.
Dual-zone capability (Figure 3) provides
two independent systems housed in one
MONITORING SYSTEMFigure 2. The MSA TriGas Monitoring System uses as many as three sensors to alert personnel of gas leak hazards.
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 30
enclosure that monitors two sample points:
Pump module #1 is assigned to 0-100% LEL
CH4 and Pump module #2 is assigned to
0-50 pm H2S and 0-25% O2.
For dry wells and applications in which a
gas monitoring station is required with use
of remote sensors (Figure 4), mounting
the gas detector on a plate assembly with
power supply, horns and strobes can meet
site compliance with NFPA 820 standards.
In pumping station applications in which
end users do not need to house the gas
detection system components within a
wall-mounted enclosure and require only
DUAL-ZONE WET WELL MONITORING SYSTEMFigure 3. This type of system provides two sample points in a single enclosure.
DRY WELL GAS MONITORING SYSTEMFigure 4. When remote sensors are required, this type of setup can comply with NFPA 820 standards.
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Wastewater eHANDBOOK: Ward Off Wastewater Woes 31
minimal features, a flow panel such can be
offered to meet basic NFPA 820 compli-
ance. This plate-mounted system includes
the necessary gas monitors, DC pump, flow
meter, three-way calibration valve and end-
line filter (Figure 5).
Other features to consider include heated
and/or NEMA 4X stainless steel enclosures;
capability with added protection to install
or handle samples in NEC Class I, Div. 1
areas where combustible gas is always
present; addition of alarm relay contacts
to meet needs of more complex alarming
logic; and additional water separator filters.
PROPER MONITORING FOR PROTECTIONMonitoring wastewater treatment plant
wells for combustible and toxic gases is
essential to protect employees, equipment
and the facilities themselves. Failing to
adhere to the requirements of NFPA Code
820 could result in an accident with tragic
or catastrophic consequences, including the
loss of life.
Multiple suppliers offer combustible and
toxic gas monitoring systems that meet
the requirements of NFPA Code 820. Their
field staffs are extremely knowledgeable
resources and welcome questions about
gas detection. The chances are excellent
that if you have a gas detection problem,
they’ve already heard it and solved it multi-
ple times at other treatment plants.
TIM WOLK is water and wastewater market sales
manager at MSA Safety. He can be reached at
WET WELL FLOW PANEL SYSTEMFigure 5. Flow panel systems such as the MSA TriGas Lite offers minimal features and can meet basic NFPA 820 compliance.
www.ChemicalProcessing.com
Wastewater eHANDBOOK: Ward Off Wastewater Woes 32
Visit the lighter side, featuring draw-
ings by award-winning cartoonist
Jerry King. Click on an image and you
will arrive at a page with the winning
caption and all submissions for that
particular cartoon.
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