Wastewater Reuse: Selected Applications

EnvH 545

Steven Drangsholt, Lesley Leggett, Jennifer Parker, Ching-Yu Peng,

Kelly Stumbaugh

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

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

Secondary Effluent

Complete Treatment

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

Chemical Addition

SECoagulation Flocculation

Sludge

Clarification

Effluent

Filtration

Chemical Addition

SECoagulation FlocculationFlocculation

Sludge

Clarification

Effluent

Filtration

Direct Filtration

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

Chemical Addition

SECoagulation Flocculation

Effluent

Filtration

Chemical Addition

SECoagulation FlocculationFlocculation

Effluent

Filtration

Effluent

Filtration

Contact Filtration

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

disinfection

Chemical Addition

SECoagulation EffluentFiltration

Optional GAC Adsorption

Chemical Addition

SECoagulation EffluentFiltration

Optional GAC Adsorption

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

Agricultural Reuse of Wastewater

• One of the most significant uses of reclaimed wastewater

• Water needed for irrigation in some states accounts for >80% 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)

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

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

Agricultural Reuse in Washington

• Foods consumed raw– surface irrigation: water requires

oxidation and disinfection with mean total coliforms < 2.2/100 ml

– spray irrigation: water requires oxidation, coagulation, filtration, disinfection and total coliforms < 2.2/100ml

• Processed foods– only oxidation and disinfection, regardless

of irrigation type, and a 7-day mean total coliforms < 240/100 ml

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

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.

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

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!!!

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

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

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

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.”

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

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

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

Residential Wastewater ReuseCommercially available greywater treatment & recycling

Residential Wastewater ReuseCommercially available greywater treatment & recycling

Residential Wastewater Reuse

Custom designed system in Sydney, Australia

Residential Wastewater Reuse

Healthy Home System in Toronto, Canada

Groundwater Recharge

California

FloridaSource: US EPA. Guidelines for water reuse

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

• 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

Groundwater Recharge - Advantages

• 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.

Groundwater Recharge – Limitations (1)

• 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

Groundwater Recharge – Limitations (2)

Source: US EPA. Guidelines for water reuse

Groundwater Recharge – Techniques

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

Groundwater Recharge – Guidelines (WA)

Source: US EPA. Guidelines for water reuse

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

Questions?