Industrial
W a
t
e
r
W o
r
l
d
Advanced Water Reuse Saves Money
By James Schaefer, P.E.
Background
and aggregate with other droplets to
create progressively larger drops,
Some of the quench water is used
to produce steam for the production
process. The hydroFigure 1: Liquid/Liquid Coalescer Medium Contruction carbon contamination in quench
water causes fouling
of the steam generators and heat exchangers, increased
wastewater flows
for treatment, and
increased
energy
and cleaning costs
for the steam system
Pre-Filter
Solids
components. The
Droplets
hydrocarbons in the
quench water have
which ultimately form a separate very low interfacial tensions which
phase for removal from the water normally lowers the efficiency of
stream. The separated phase typically other removal systems.
is recycled back into the process to
A Pall liquid/liquid coalescer was
create additional savings. Because the installed at the plant in late 1997 to
coalescer medium has a section with remove the hydrocarbon contamismall pore sizes, the coalescer should nants from quench water. Because of
be protected with a prefilter to the unique surface-modified medium
remove particles that would plug the and the proprietary system design, the
medium and significantly reduce effi- coalescer has reduced the hydrocarciency and service life.
bon concentrations to 5 to 15 ppmv.
Oil and Other Hydrocarbon Separation from Water
Liquid/liquid coalescers commonly The reduced hydrocarbon contaminaDispersed oil or hydrocarbons can are used in refineries to clean process- tion has saved over $300,000 per year
be separated from water using liq- quench waters for subsequent recov- in the operation of the steam system,
uid/liquid coalescers, which also can ery and reuse. A European ethylene and decreased heat exchanger fouling
separate other dispersed liquids, such plant faced the dilemma
as ammonia or methanol, from a of hydrocarbon contami- Figure 2: Membrane Bio-Reactor (MBR) Schematic
process stream. The ability to sepa- nation of quench water
rate a liquid dispersion depends upon from ethylene produc- Wastewater
Biological
Treatment
the physical properties of each liquid, tion process. Quench
such as the relative specific gravity of water is used to separate
each liquid, and the properties of the pyrolysis gases, includseparation medium. Coalescers are ing benzene, toluene,
Treated
Returned, Concentrated
specialized filters that intercept small xylene, styrene, ethylWastewater
Bio-Solids
Discharge
droplets of the dispersed liquid on the benzene, and napthenes,
Crossflow
filter medium. As shown in Figure 1, from the ethylene prodMR or UF
the droplets flow along the medium uct.
Reprinted with revisions, from the December 2000 edition of INDUSTRIAL WATER WORLD
Copyright 2000 by PennWell Corporation
Industries spend large amounts of
money to purchase water to meet production demands, and treat and dispose of the resulting wastewater discharges. Water reuse has become an
attractive alternative to once-through
use of water, especially in areas faced
with water shortages. Industries have
minimized the costs of water supply,
wastewater treatment and disposal by
using advanced water treatment to:
• Recover useable products from
wastewater streams
• Recover process water for other
uses in the plant
• Provide a drought-proof water
supply for industry
• Save money spent on waste disposal and water purchases
• Increase manufacturing efficiency
and reduce waste discharges
• Conserve limited water supplies
for potable uses
• Improve wastewater treatment
operations and reduce impacts on
the environment
and other required maintenance for
the equipment. The separated hydrocarbons are recycled and blended into
gasoline products. Water treatment
costs also were reduced significantly.
and pulp and paper. In the future,
these systems are likely to find wide
application on ship-board wastewater
treatment and reuse.
oride (PVDF) membrane is chlorine
and oxidant resistant, which gives the
operators flexibility to disinfect the
filtered water, and to clean and disinfect the microfiltration system.
General Water Reuse After Microfiltration
In northern California, a Pall
Wastewater Treatment With Membrane Bioof Wastewater Effluent
microfiltration system is providing
Reactors
Secondary treated wastewater tertiary filtration of over 3 mgd of
Industrial wastewater treatment effluent typically has 10 to 30 mg/L of secondary effluent to supply irrigacan be subject to process upsets BOD and suspended solids, plus large tion water for nearby municipal and
because of rapid changes in waste- numbers of pathogenic bacteria and industrial landscaping and other nonwater characteristics. A biological protozoa, such as Giardia and potable water uses. This water reuse
treatment system is vulnerable to dis- Cryptosporidium. These characteris- is important to conserve fresh water
persed or filamentous
supplies for human
Figure
3:
General
Water
Reuse
Using
Microfiltration
growth, if the wastewater
consumption, irrigation
Activated Sludge
is nutrient deficient. Under
of edible crops, and
these conditions, the bio- Raw
other high quality uses.
Wastewater
Water for
Primary
Aeration
Secondary
logical solids can be
Water reuse also proIndustrial Reuse
Clarifier
Clarifier
or Irrigation
washed out of the clarifier
vides a secure supply of
Microfiltration
in a typical activated
water, even during
sludge system, resulting in
droughts, for less critipoor performance and poor effluent tics create aesthetic and public health cal water demands.
quality. A membrane bio-reactor can problems for recycling and reuse of
In some instances, phosphorus
overcome this problem by providing this water. With respect to aesthetics, removal may be required prior to
excellent solids separation regardless the suspended solids can deposit on reuse. A pilot test in Colorado
of the condition of the biological surfaces and create an unpleasant showed
excellent
phosphorus
solids.
film, or the solids can settle in tanks removal and microfiltration performThe membrane bio-reactor consists and piping creating odorous, septic ance with the addition of 20 mg/L of
of an aeration tank to grow the bio- conditions. In addition, the suspended ferric chloride before the Pall unit. In
logical solids and treat the waste- solids can clog small openings in pip- fact, design fluxes on the microfilter
water, and a membrane filtration sys- ing and equipment, which increases increased by about 25% in spite of
tem to separate treated water from maintenance requirements and costs. the higher solids load from the iron
the biological solids, as shown in With respect to public health, the hydroxide floc.
Figure 2. The system can use a con- pathogens are a hazard to people, if
tinuous flow aeration tank, or a people contact the water or aerosols High Quality Water Reuse With Integrated Membrane
sequencing batch reactor (SBR) for from water sprays. Tertiary filtration Systems
Integrated membrane systems
smaller flow systems. The membrane of secondary effluent using a microfilfiltration system may be immersed in ter, as shown in Figure 3, will remove process secondary effluent and prothe aeration or SBR tank, or installed virtually all of the suspended solids, duce very high quality water for
as a separate crossflow filtration sys- bacteria, and protozoa. After appro- industrial uses and ground water
tem.
priate disinfection, the water is suit- recharge. The integrated membrane
Effluent quality is very consistent able for limited human contact, such systems use a combination of microbecause the membrane system as irrigation of landscaping, golf filtration and reverse osmosis (see
Figure 4) to remove suspended solids,
removes virtually all of the biosolids courses, or industrial cooling water.
for recycle to the aeration tank, which
Long-term testing at Orange dissolved salts and organic combacteria,
Giardia,
maintains a high level of biological County Water District (California) pounds,
treatment, and produces clear, well- using a Pall 0.1 micron hollow fiber Cryptosporidium, and most viruses
the
secondary
effluent.
treated effluent for discharge or reuse. microfiltration
system
showed from
Membrane bio-reactors typically are 99.99% to 99.99999% (4 to 7 logs) Integrated membrane systems are
used for high strength or difficult to removal of coliform bacteria, Giardia, becoming common in areas of the
treat wastewater, such as those with and Cryptosporidium. In fact, virtual- United States with large water
nutrient deficiency. Applications ly no coliform bacteria or cysts have demands and limited available supinclude treatment of wastes from tan- been detected in the microfiltered plies, such as California, Arizona, and
neries, food processing, breweries, water. The tough, polyvinylidene flu- Texas.
The integrated membrane Figure 4: High Quality Water Reuse with IMS
to lower costs and to obtain
systems represent a signifia drought-proof water supActivated Sludge
cant improvement over
ply. An electronics manufacreuse systems that use con- Raw
turer in southern California
Wastewater
Primary
Aeration
Secondary
ventional lime coagulation
purchased a 0.2 mgd moduClarifier
Clarifier
Microfiltration
and granular media filtralar Pall microfiltration systion as pretreatment. The
tem to process secondary
Reverse Osmosis
microfiltration first stage
effluent and produce feed
High Quality Water for
consistently produces filwater for its polishing water
Industrial Reuse
tered water with turbidity
treatment system. The reuse
less than 0.05 NTU, and a
system allowed the manufacsilt density index less than 2.
turer to stop buying potable
Silt density index is a measure of the lower operating costs for the pretreat- water from the local water supplier.
fouling potential for a reverse osmosis ment stage.
During droughts, the supply of
process. Conventional pretreatment
Successful integrated membrane potable water might be reduced or
has difficulty in producing consistent system projects include treating even interrupted, which could limit
water quality, even at values twice wastewater from a computer chip manufacturing operations. The reuse
those of microfiltered water. Because manufacturing facility for ground system will allow the manufacturer to
of the higher quality water, the allow- water recharge in southern Arizona, operate at full capacity at all times
able loading on the reverse osmosis and treating secondary wastewater and conserves the potable water supsecond stage can be increased by 20% effluent for use as boiler make-up ply. IWW
and chemical cleaning intervals for water at an oil refinery in southern
About the author: James Schaefer
the reverse osmosis units increased to California. A proposed cogeneration
serves as Vice President for Pall Water
several months. Microfiltration recov- facility in New Jersey also developed
Processing with responsibility for
eries typically are 90% to 95%; and plans for an integrated membrane sysproduct development and applicathe microfiltration wastewater can be tem to produce 5 mgd of boiler maketions. His experience spans 28 years
easily recycled back to the wastewater up water, at a cost lower than the cost
of design and operation of water and
treatment. Other benefits of using of purchasing water from the local
wastewater facilities as a licensed promicrofiltration include 75% smaller water supplier.
fessional engineer. He can be reached
area requirements compared to conSmall industries have successfully
by E-Mail at jim_schaefer@pall.com.
ventional pretreatment and 40% implemented this type of water reuse
2200 Northern Boulevard
East Hills, New York 11548-1289
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Lit Code IWW 12/00
Purifying intake water.Treating segregated
process streams. Recycling wastewater.
Manufacturers need their water to work
hard to reduce water use and lower
operating costs.To get more cycles from
your water and to discover the widest
range of energy-saving, cost efficient, rapid
payback membrane water treatment systems
call Pall Water Processing at 1.888.873.7255
(in NYS call 1.516.484.5400) or visit our
web site at www.pall.com/thefutureofwater.
recycling
making water work harder