There are a range of approaches that are used globally to address the basic human need for sanitation and waste disposal. The following is a non-comprehensive list of the main approaches used, ranging from the simplest to the most “sophisticated”. Ironically some of the more “sophisticated” are in fact the least ecological and highest emission options. It is time to reappraise the fundamentals of how ecosystems deal with waste and purify water and then mimic those processes to come up with a better and lower cost approach to dealing with our most fundamental human need.

Onsite systems

• Human manure direct to garden systems (used extensively in China even today)

  • low cost

  • spreads disease and parasites

  • odour

  • recycles nutrients for food production

• composting toilets

  • nutrients can be recovered for food production

  • odours common

  • requires power for ventilation fans

  • insect disease vectors - particularly scuttle flies are difficult to control

  • parasitic worms can encyst and survive for years

  • needs no water for flushing

  • needs separate greywater treatment infrastructure

  • some larger systems can treat food wastes and other organic matter and paper

  • can require the addition of lime or organic matter/sawdust

  • final product must be buried for safety

• wet composting/vermiculture treatment

  • can be configured without a tank as proposed for GOSEP

  • nutrients can be recovered

  • conventional plumbing can be used

  • treats all human waste and greywater

  • periodic but infrequent compost harvesting is required

  • parasitic worms can survive composting so harvested vermicompost must be buried

  • needs electricity for effluent pumping depending on the site slope and configuration

  • low or no odour due to the odour adsorption properties of humus

  • passive oxygenation means no electricity is required for the process to work

  • needs irrigation/dispersal field

• septic tanks

  • requires a large tank

  • moderate cost to install

  • need no electricity to operate

  • requires periodic sludge collection infrastructure

  • ground and surface water contamination

  • odour and methane emissions

  • widely accepted and used as default in developed countries and developing country urban and rural areas

  • needs a relatively large dispersal field for effluent generated because anaerobic effluent (blackwater) is harder to treat than aerobic effluent

  • dispersal fields fail during prolonged rain or flooding

• onsite aerobic treatment (main types only)

  • activated sludge

  • trickling filter

  • Rotating Biological Contactors (RBC)

  • sand filter

  • all require regular costly maintenance

  • sludge collection from septic pretreatment or sedimentation phase

  • all require electricity for pumping

  • capital intensive

  • odours from septic phase if present

  • conventional plumbing

  • most require effluent disinfection prior to dispersal

• EcoSan

  • recovers urine separately for agriculture

  • can be “dry” or use flushing system

  • odours difficult to control

  • requires power for ventilation

  • high cost and high maintenance

  • cultural acceptance is problematic

  • grey water is not treated

• chemical toilets

  • predominantly used for mobile or temporary application

  • requires addition of chemicals

  • waste product difficult to treat

  • requires dedicated collection infrastructure

  • odour emissions

  • not ecologically sustainable

• incinerating toilets

  • high greenhouse emissions

  • safety considerations

  • lost benefit of organic matter

  • only viable for very cold or dry locations

  • not environmentally sustainable

• Biogas systems

  • suitable for warm/ tropical environments

  • can be combined with animal manure and other organic waste treatment

  • produces a valuable cooking or power generation fuel

  • requires hydrogen sulphide removal to prevent corrosion and odour emissions

  • needs large storage bladders for biogas

  • costly to set up and maintain

  • safety precautions required

Community based systems

• In field defecation

  • typically in rural areas but also common in some third world cities

  • disease vector if not buried immediately

  • public and undignified

  • can recycle nutrients and organic matter for food production

  • low cost

• Night cart collection systems

  • formal collection of human wastes

  • odour both in storage and collection

  • requires formal collection infrastructure

  • disease vectors

  • expensive to operate

  • unpleasant work for collectors

  • requires disposal away from collection area

• Open stormwater drains

  • odours in and around drains and vents

  • relies on regular rain to flush away human wastes

  • pollutes waterways

  • spreads disease

  • disease vectors and drinking water contamination

  • low cost infrastructure

  • high healthcare and mortality cost

• Sewerage collection

  • formal drainage pipework

  • reduces odour and contamination from streets and houses

  • blockages and overflows common if not designed well

  • introduces the need for flushing toilet systems

    • squat flush toilets

    • flush pedestal (Western style toilets)

    • pour flush squat toilets

  • contaminates waterways and “receiving” waters

  • spreads disease especially during flooding or heavy rain

  • high cost of installation

    • high energy requirements for manufacture and maintenance of sewerage hardware

    • pipes

    • excavation

    • pump stations

    • pumps

    • vents and odour control

    • corrosion repairs

    • blockages

  • reduces local disease vectors

  • subject to raw sewage overflows during flooding

  • high cost of maintenance

  • contamination and eutrophication of receiving waters

  • nutrients are permanently lost

  • effluent disposal or treatment is still needed

  • collection system can represent more than 80% of the total cost of sewerage infrastructure

• Sewage treatment

  • raw sewage discharge to receiving waters

    • spreads disease

    • contaminates ecosystems

    • pollutes receiving waters

    • nutrients lost to agriculture

    • can cause toxic algal blooms

    • pollutes beaches

  • screening only

    • sewage is screened to remove plastics, condoms, sanitary products and other identifiable sewage components

    • still spreads disease

    • still contaminates the environment

    • still wastes nutrient resources

    • primary treatment

  • open settling /oxidation ponds

    • minimal treatment

    • requires long retention times

    • odours are a problem

    • relatively low cost

    • flooding rain can cause environmental contamination

    • water birds and animals attracted to the ponds can be disease vectors and viral hosts

  • biogas anaerobic treatment

    • sometimes used to recover enough energy to run the subsequent treatment steps

    • gas recovered

    • useful source of energy

    • odour

    • sludge disposal cost

    • high maintenance

    • can require heating to work efficiently in cold areas

    • high capital cost

    • corrosion problems

    • effluent quality is low without further treatment

    • disease can be spread by effluent and sludge

• Secondary treatment

  • activated sludge

    • sludge disposal

  • high energy required to treat sewage

  • nutrient contamination of receiving waters

  • toxic disinfection by-products due to organic matter suspended in the effluent

  • capital intensive

  • high maintenance

  • odours

  • diseases particularly virus’ still present even after chlorine disinfection

  • stormwater infiltration to collection system can result in raw sewage discharges during heavy rainfall

  • nutrient contamination and algal blooms still a problem if discharged to water systems

• Advanced tertiary treatment and recycling

  • very expensive

  • high maintenance

  • recycle system infrastructure required

  • high verification cost

  • high risk if final effluent is not up to recycle standard

  • high flows during flooding events still problematic

  • requires preliminary biological pretreatment with all of the attendant issues listed above

    • screening

    • primary treatment

    • secondary treatment

    • disinfection

    • nutrient removal

    • very high energy required

    • manufacture of equipment & membranes

    • filtration pumping

    • reverse osmosis

    • distribution of effluent

    • discharge to land

• Soil treatment via land application (sewerage farm)

  • requires land available near the city to avoid costly long distance pumping

  • soil infiltration process is relatively energy efficient

  • reoxygenation is rapid

  • can be located away from urban areas

  • nutrients can be recovered for agriculture

  • sunlight reduces pathogen load

  • odours especially if anaerobic primary pretreatment is used

  • wet weather storage is critical to avoid waterway contamination

  • animals exposed to the land application area can be disease vectors

• STED/SETEP Septic tank effluent pumping or draining networks

  • still requires pretreatment infrastructure

    • septic

    • wet composting

    • secondary on site systems

  • pumping cost is reduced compared to sewage

  • for STED no pumping cost depending on lay of the land

  • sludge management is still required

  • septic pump out infrastructure is required

  • can be suitable for soils with poor drainage

  • still need to be able to store or reuse the effluent collected

  • effluent can be used for irrigation during dry times

• VIP toilets

  • relatively low cost

  • odours

  • flies and insect vectors

  • low user acceptance

  • doesn’t require water for flushing

  • can contaminate ground water and drinking water

• Landfill collection and disposal

  • in developed countries some sanitary wastes are disposed of to landfill

  • infant and adult nappies/diapers

  • sanitary products

  • tampons

  • pads

  • food wastes

  • paper wipes

  • in many Asian countries sewer systems are not designed to take toilet paper

  • nutrients and organic matter lost

  • energy intensive

  • high management and logistics requirement