What is wastewater treatmentWhat is wastewater treatment

• Usually refer to sewage treatment, or domestic wastewater treatment

• process of removing contaminants from wastewater, both runoff and domestic

GoalsGoals• Wastewater treatment systems take human and

industrial liquid wastes and make them safe enough (from the public health perspective) to return to the aquatic or terrestrial environment.

• In some cases, wastewater can be clean enough for reuse for particular purposes.

• Wastewater treatment systems use the same processes of purification that would occur in a natural aquatic system only they do it faster and in a controlled situation.

Where does wastewater come from?Where does wastewater come from?

• Sewage or wastewater is composed of sewage or wastewater from:– Residences (used kitchen and bathroom

wastes– Rainwater)

– Livestock wastes– Industrial effluent (usually require specialized

pretreatment process)

How can it be treated?How can it be treated?

• collected and transported via a network of pipes and pump stations to a municipal treatment plant

Types of treatmentTypes of treatment• Mechanical treatment

– Influx (Influent) – Removal of large objects – Removal of sand and grit – Primary Sedimentation

• Biological treatment– Trickling bed filter– Activated sludge

• Chemical treatment– Disinfection

Wastewater TreatmentWastewater Treatment

• Types of treatment systems include: Septic Tanks or Wastewater Treatment Plants (WWTPs).• Septic Tanks typically treat small volumes of waste (e.g., from a single household, small commercial/industral)

• WWTPs typically treat larger volumes of municipal or industrial waste.

Treatment stages - Primary Treatment stages - Primary treatmenttreatment

• typical materials that are removed during primary treatment include– fats, oils, and greases (aka FOG)– sand, gravels and rocks (aka grit)– larger settleable solids including human

waste, and – floating materials

Septic TanksSeptic Tanks• Approx. 22 million systems in operation

( 30% of US population)• Suitability determined by soil type, depth to

water table, depth to bedrock and topography

• Commonly fail due to poor soil drainage• Potential contaminants: bacteria, heavy

metals, nutrients, synthetic organic chemicals (e.g. benzene)

Waste Water Treatment PlantWaste Water Treatment Plant

Waste Water Treatment PlantWaste Water Treatment Plant

Waste Water Treatment PlantWaste Water Treatment Plant• Primary Sedimentation

Tank– Remove grease, oil– Fecal solid settle, floating

material rise to the surface

– Produce a homologous liquid for later biological treatment

– Fecal sludge are pumped to sludge treatment plant

Treatment stages - Secondary Treatment stages - Secondary treatmenttreatment

• Degrade biological content (dissolved organic matter) of the sewage– Ex: human waste, food waste, soaps,

detergent• Added bacteria and protozoa into sewage• 3 different approaches

– Fixed film system– Suspended film system– Lagoon system

Three approachesThree approaches

• Fixed Film Systems– grow microorganisms on substrates such as

rocks, sand or plastic – wastewater is spread over the substrate– Ex: Trickling filters, rotating biological

contactors

Treatment stages – Tertiary Treatment stages – Tertiary treatmenttreatment

• remove disease-causing organisms from wastewater

• 3 different disinfection process– Chlorination– UV light radiation– Ozonation

What can effluent use for?What can effluent use for?

• discharged into a stream, river, bay, lagoon or wetland

• used for the irrigation of a golf course, green way or park

• If it’s sufficiently clean, it can be used for groundwater recharge

Advanced TreatmentAdvanced Treatment

• Nitrogen removal– Ammonia (NH3) → nitrite (NO2

-)→ nitrate (NO3-)

• Phosphorous removal– Precipitation with iron or aluminums salt

• Lead to eutrophication• May cause algae bloom

Sludge treatmentSludge treatment

• Primary sludge usually have strong odors• Secondary sludge have high concentration

of microorganism• Goals of treatments are:

– Reduce odors– Remove water reduce volume– Decompose organic matter

Sludge disposalSludge disposal

• Superheat sludge and convert into small granules that are rich in nitrogen– Sell it to local farmer as fertilizer

• Spread sludge cake on the field• Save landfill space

The Clean Water ActThe Clean Water Act

• Requires reduction of pollutants entering all surface water

• Strict requirements for wastewater treatment plants

• Control of non-point source pollution• Tighter controls on toxic pollutants

• In 1948 Congress passed a bill to provide federal funds for constructing wastewater treatment facilities

• Mandated that by 1983 the nation’s waterways should be fishable and swimmable

• By 1995 discharges to waterways should be eliminated

• Standards defining the levels of pollutants acceptable for discharge were called effluent limitations

Safe Drinking Water ActSafe Drinking Water Act

• Written in 1974, amended in 1986• Protects drinking water resources• Requires adherence to established

drinking water standards • Protects underground sources including a

wellhead protection program

Basic Required ActivitiesBasic Required Activities

• Establish and enforce Maximum Contaminant Levels MCL’s

• Monitoring of contaminants• Filtration of water from surface water

sources• Regulation of the use of lead materials in

public water supply systems• Wellhead protection

Waterborne DiseaseWaterborne Disease

• Typhoid• Dysentery• Cholera• Infectious hepatitis• Amoebic dysentery• Giardiasis• Gastroenteritis• Cryptosporidiosis

Chemical ContaminantsChemical Contaminants

• Minerals dissolved from rocks and soil• Pesticides and herbicides• Leaking underground storage tanks• Industrial effluents• Seepage from septic systems• Wastewater treatment plants • Landfills