Wastewater Reuse: Selected Applications

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Wastewater Reuse Selected Applications

• EnvH 545
• Steven Drangsholt, Lesley Leggett,
• Jennifer Parker, Ching-Yu Peng,
• Kelly Stumbaugh

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Wastewater Plant Standards

• Some states have guidelines, some have
  regulations
• Washington has guidelines
• EPA Suggested Guidelines
• pH 6-9
• BOD5 10 mg/L
• Turb. 2 NTU
• E. coli NONE
• Res. Cl2 1 mg/L

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EPA Guidelines

• Urban Reuse
• Restricted-Access-Area Irrigation
• Agriculture Reuse
• Recreational Impoundments
• Landscape Impoundments
• Construction Uses
• Industrial Reuse
• Groundwater Recharge
• Indirect Potable Reuse

Disinfected, Tertiary Treated Effluent can be
used in all of these Applications
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Secondary Effluent
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Complete Treatment

• Expensive!!!!
• Filter can be several units
• Chemical Addition depends on SE

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Direct Filtration

• No clarification reduces solids production
• SE should be less than 10 NTU
• Filtration step may have several units

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Contact Filtration

• No Floc Step, No Clarifier
• Relies on in-line coagulation
• Can produce equivalent virus kill with
  disinfection

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How Effective?
Constituent After secondary with BNR plus disinfection After secondary with BNR plus depth filtration and disinfection After secondary with BNR plus microfiltration, RO and disinfection
TSS 5-20 1-4 1
BOD 5-20 1-5 0-2
TN 2-12 2-12 1
NO3 1-10 1-10 1
Phosphorus 0.1-0.5 0.1-0.5 0.5
Turbidity 2-6 2 0.1 -1
Bacteria 2.2-240 2.2 0
Protozoan 5-10 1 0
Viruses 100-10000 .0001 0
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Agricultural Reuse of Wastewater

• One of the most significant uses of reclaimed
  wastewater
• Water needed for irrigation in some states
  accounts for gt80 of demand
• Regulations and guidelines vary widely from state
  to state
• Guidelines for food crop use (21 states) and
  non-food crop use (40 states)

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Benefits of Agricultural Reuse

• High concentrations of nutrients
• May eliminate need for fertilizer
• Long-term soil enrichment
• Decreases demand on potable water supply
• Additional treatment in soil
• Water not discharged to receiving waters

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Disadvantages of Agricultural Reuse

• Health risk from associated pathogens
• Health risk from other contaminants (e.g. metals,
  chemicals, pharmaceuticals)
• Decrease in soil quality from accumulation of
  metals and acidification
• Infiltration of groundwater

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Agricultural Reuse in Washington

• Foods consumed raw
• surface irrigation water requires oxidation and
  disinfection with mean total coliforms lt 2.2/100
  ml
• spray irrigation water requires oxidation,
  coagulation, filtration, disinfection and total
  coliforms lt 2.2/100ml
• Processed foods
• only oxidation and disinfection, regardless of
  irrigation type, and a 7-day mean total coliforms
  lt 240/100 ml

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Urban Wastewater Reuse

• What is recycled urban wastewater or reclaimed
  water?
• Urban wastewater that has undergone additional
  treatment following secondary treatment in order
  to be reused rather than discharged into the
  environment
• Can reduce strain on potable water supply

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Urban Wastewater Reuse

• What can urban reclaimed water be used for?
• Irrigation - public parks, schools, road medians,
  any landscaped areas, golf courses
• Commercial - vehicle washing facilities, laundry
  facilities, window washing, mixing pesticides and
  herbicides
• Construction - dust control, concrete production
• Toilet and urinal flushing
• Fire protection
• Drinking water?? in Australia, not yet in the
  U.S.

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Urban Wastewater Reuse

• A reclaimed water system consists of
• Water reclamation facility - provides treatment
  in addition to secondary treatment
• Distribution system - includes pipelines, storage
  facilities, pumping facilities

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Urban Wastewater Reuse

• Reclaimed water distribution system is a dual
  distribution system
• Network of pipes to deliver reclaimed water to
  the public
• Run separate but parallel to potable water
  pipelines
• Potential problem????
• CROSS CONNECTIONS!!!

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Urban Wastewater Reuse

• Major considerations are public health and
  reliability of the system
• Water must be of acceptable quality for intended
  uses
• System must be maintained and operated properly
• Reclaimed water pipes must be clearly marked

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Urban Wastewater Reuse

• Retrofitting reclaimed water system in existing
  cities can be expensive
• BUT can be cost-effective if
• Water supply is of poor quality
• Water supply does not meet demand
• Advanced wastewater treatment already required

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Urban Wastewater Reuse

• St. Petersburg, FL
• Using reclaimed water system since 1977
• Provides for residential commerical properties,
  baseball stadium, schools
• San Diego, CA
• Ponoma, CA
• Serves CA Polytechnic Institute, paper mills
• Austin, TX
• Tucson, AZ

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Urban Wastewater ReuseIn the news

• California county turns to sewer water to
  increase drinking supplies
• International Herald Tribune, Nov. 27, 2007
• On Friday, the Orange County Water District will
  turn on what industry experts say is the world's
  largest plant devoted to purifying sewer water to
  increase drinking water supplies. They and others
  hope it serves as a model for authorities
  worldwide facing persistent drought, predicted
  water shortages and projected growth.
• San Jose-area water officials announced a study
  of the issue in September, water managers in
  southern Florida approved a plan last week
  calling for abundant use of recycled wastewater
  in the coming years in part to help restock
  drinking water supplies, and planners in Texas
  are giving it serious consideration.

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Residential Wastewater Reuse

• Why reuse wastewater at home?
• Conserve precious drinking water supply
• Droughts
• Arid climates
• Overuse or population overwhelming supply
• Save money
• Reduce environmental impact associated with
  wastewater treatment disposal

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Residential Wastewater Reuse

• Greywater
• Wastewater from sinks, bathtubs, showers, dish
  washer, laundry (anything except toilets)
• May contain pathogens, likely to contain other
  microbes, detergents, FOGs, bleach, hair, food
  particles, suspended solids
• Not for potable reuse unless tertiary treatment

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Residential Wastewater Reuse

• Simple home water reuse
• Collect warming tap water in bucket
• Hose from sink drain to outdoors planter box
• More complex home water reuse
• Divert greywater to underground lawn/garden
  irrigation system
• Commercial treatment reuse systems

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Residential Wastewater Reuse

• Commercially available greywater treatment
  recycling

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Residential Wastewater Reuse

• Commercially available greywater treatment
  recycling

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Residential Wastewater Reuse

• Custom designed system in Sydney, Australia

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Residential Wastewater Reuse

• Healthy Home System in Toronto, Canada

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Groundwater Recharge
California
Florida
Source US EPA. Guidelines for water reuse
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Groundwater Recharge - Purposes

• establish saltwater intrusion barriers
• provide further treatment for future reuse
• increase potable or nonpotable aquifers
• provide storage of reclaimed water for subsequent
  retrieval and reuse
• control or prevent ground subsidence

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Groundwater Recharge - Advantages

• Less cost than equivalent surface water
  reservoirs
• The aquifer serves as an eventual natural
  distribution system
• No evaporation, taste and odor problems occurred
  in surface reservoirs
• Suitable sites for surface water reservoirs may
  not be available or environmentally acceptable

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Groundwater Recharge Limitations (1)

• Extensive land areas may be needed for spreading
  basins
• Costs for treatment, water quality monitoring,
  and injection/infiltration facilities operations
  may be expensive.
• Recharge may increase the danger of aquifer
  contamination due to inadequate pretreatment.

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Groundwater Recharge Limitations (2)

• Not all recharged water may be recoverable
• Hydrogeologic uncertainties may reduce the
  effectiveness of the recharge project in meeting
  water supply demand
• Inadequate institutional arrangements or
  groundwater laws may not protect water rights

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Groundwater Recharge Techniques
Source US EPA. Guidelines for water reuse
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Groundwater Recharge Guidelines (WA)
Treatment Oxidized, coagulated, filtered, and disinfected
BOD5 5 mg/l
TSS 5 mg/l
Turbidity 2 NTU (Avg) 5 NTU (Max)
Total Coliform 2.2/100 ml (Avg) 23/100 ml (Max)
Total Nitrogen Not specified
Source US EPA. Guidelines for water reuse
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Conclusions

• Many current uses for recycled wastewater
• Varying levels of treatment required
• Pros
• Conserve potable water
• Reduce effluent to environment
• Cons
• Health safety precautions necessary
• Careful planning needed
• Potential for much greater use in future

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Questions?