Technologies to improve the water environment with bio-toilets

Needs Address

The need to reduce the impacts of deteriorating quality of public water body as a result of climate change, in areas that may face declining sanitation conditions. Particularly applicable in response to the need to mitigate impacts in regions where water pollution is occurring due to urban population growth associated with economic growth, or due to rapid industrial development. 

Adaptation effects

• Limiting the deterioration of water quality in enclosed water bodies due to the effects of climate change, etc., 
• Prevention of deterioration of sanitation conditions and reduction of disease risk due to climate change 
• Improved wastewater treatment capacity to deal with extreme events

Overview and Features

• The bio-toilet is a technology that will contribute to improvement of the water environment, by preventing the dumping of raw sewage by railways, promoting proper treatment of toilet wastewater in mountainous areas and tourist areas, preventing raw sewage dumping at rapidly growing construction sites, and so on. Sawdust is added the tank, and mixed with urine and other human waste, to decompose and convert to compost. There are two types: a railway car onboard type, and an on-site placement type. 
• The residue can be used in the making of compost, or converted to energy.

Design and functioning of the bio-toilet

Source: Model project for improvement of the Asian water environment, 2012 (Using biotoilets to improve the water environment)

Cost

Railway Car Onboard Bio-Toilet

• Manufacturing cost (initial cost): About 1 million yen per unit
• Waste treatment cost (including human waste transport cost): About 1 million yen per unit
• Maintenance cost: Almost no cost, if routine check is done
• On-Site Bio-Toilet

  Comparison of installation and maintenance costs

  	Cost to install (10,000 yen )	Maintenance costs (10,000 yen) per 20 years	Cost burden per person per year (10,000 yen)
  Septic Tank	9	120	1.29
  Stand-alone johhasou system	22	72	0.94
  Bio-toilet	12	3	0.12

  Source: Model project for improvement of the Asian water environment, 2012 (Using biotoilets to improve the water environment)

Energy source

Electricity

Ease of maintenance

Routine servicing is required. 

Technology performance

Railway Car Onboard Bio-Toilet

Installation of a treatment tank capable of handling 100 uses per day (140 x 100 x 86 cm) can completely eliminate discharge into rivers of human waste originating from railway toilet sewage.

On-Site Bio-Toilet

Can be expected to reduce inflowing pollutant load (COD) (17% to 28%) *  diffusion ratio (see note).

Note: Estimated based on assumption that domestic wastewater is almost completely untreated. 

Considerations

Railway Car Onboard Bio-Toilet

• If odors are noticed to be arising during the transport of waste or from the treatment tank, it may be necessary to install a deodorizing unit into the exhaust process, and this may increase costs.
• For further cost reductions, it is necessary to conduct work such as machining, assembly, and operation checks on-site.

On-Site Bio-Toilet

• In the case of Vietnam, since more than 50% of agricultural land is in paddy fields, it could be appropriate to use rice straw, chaff, and other agricultural waste from rice-growing. In such cases, it is important to have a plan in place that includes rice straw and chaff in the supply chain of compost collection, transport, and use.

To control running costs, it is advisable to use a toilet bowl designed to take the urine separately, and to collect the urine and feces separately, as urine requires energy for evaporation. This approach would be better than the type commonly used in Japan, which uses an electric heater to evaporate the moisture. In addition, separate collection of urine and feces permits the use of a smaller composting reactor. For example, a 100-liter reactor, using about 50 liters of medium, could provide two to three months of continuous waste treatment for a five-person household. 

Co-benefit, suitability for developing countries

Benefits in Improving Health and Sanitation

• Improves access to safe drinking water.
• Prevents the spread of parasitic infections, cholera, and other diseases.
• Eliminates unpleasantness and improves comfort of living conditions.

Economic Benefits

• Significantly less expensive than initial and running costs of installing sewage treatment facilities. 
• Composting is better for the environment and is useful for soil improvement, and can significantly increase agricultural yields. 
• New employment is created by development of maintenance system for the bio-toilets. 

Information Resources

• Asia Water Environment Improvement model project, Japan Ministry of the Environment (JP)
• Model project for improvement of the Asian water environment, 2012  (Using biotoilets to improve the water environment)