Faecal sludge management – technical developments in South Asia

By Remi Kaupp, Programme Officer – Urban, and Puneet Srivastava, Manager Policy – Urban, WASH and Climate Change, WaterAid India

WASH Matters

12 Sep 2014

In urban areas, providing sanitation for all is a notoriously complex challenge, especially when trying to find alternatives to expensive sewerage systems. Faecal sludge management (FSM) is gaining more attention (e.g. by the Water and Sanitation Programme) as a crucial link in delivering on-site sanitation because both its collection through pit emptying and its treatment are usually expensive, neglected and poorly developed.

However, WaterAid engineers in South Asia are tackling this issue in several exciting ongoing initiatives.

In Bangladesh, research started two years ago on drying bed methods, in which sludge is poured out by tankers and left to become dry, sterile and compact. The research has shown how best to cover the beds to increase temperature and reduce drying time, and how to dispose of liquid effluent. The next step is to pilot co-composting – mixing the dry sludge with poultry litter and compostable solid waste to produce valuable fertiliser.

Challenges of FSM application

In India, a new research collaboration between the University of Delaware, USA, and WaterAid America/India is focusing on the use of vapour-permeable membranes to address some of the biggest FSM challenges and promote urban (and possibly rural) sanitation:

  1. How to enhance the drying rate of sludge
  2. How to contain sludge safely to avoid groundwater pollution in pit toilets
  3. How to provide alternative technologies for FSM in slums where people do not have a space on the ground and want to construct a toilet with on-site systems

Eco vapour toilets

This year, the proposed collaboration is planning to pilot breathable membranes – which allow only water vapour to come out of a membrane enclosing faecal sludge – in varied contexts across ten locations in five cities (Delhi, Puri, Kanpur, Raisen and Velankanni).

WaterAid India has suggested a new name for pilot toilets using these new membranes: eco vapour toilets. The project team plans to pilot the new toilets in congested urban slums using discarded plastic drums lined with a membrane enclosure and twin drum systems located on the first floor. The team will also pilot the eco vapour toilets in school toilet blocks using bio-digesters lined with membranes, and in household pits using twin-pit pour-flush toilet technology. The vapour-condensed water that is collected outside the membrane below the pit is pathogen-free so can enter drainage channels or absorbent cushions, whereas the drum collects only compacted sludge for later emptying. This process could make collection in dense urban centres easier.

Passive ventilation around the membrane (diagram)
Application 1: Passive ventilation around (or through) the membrane

Enclosue for above gground waste collection (diagram)
Application 2: Enclosure for above-ground waste collection

Passive ventilation around the membrane in  pits (diagram)
Application 3: Passive ventilation around (or through) the membrane in Pits

Pakistan’s solution

In Pakistan, a sewage treatment unit (STU) has been developed as a low-cost, compact method of treating waste from flush toilets. The STU is a simple septic tank, which uses an ‘effective microbe’ solution (a simple mixture of macerated raw sugar syrup and rotten fruit) for more effective treatment. The STU is being improved in two ways:

  • For rural and peri-urban areas, there is an anaerobic baffled reactor (a septic tank with several internal walls) with an anaerobic peat filter (similar to the effective microbe solution). The baffles help treat the waste and make sure the effluent contains fewer pathogens.
  • For urban areas, a membrane-based septic tank is being tested whereby, like in India, a semi-permeable membrane helps to filter pathogens from the water being released. Tests have so far shown very good pathogen removal.

Across the whole South Asia region, a mapping exercise is ongoing to assess how FSM is considered and carried out by target municipalities. This exercise will help inform what our key role can be when piloting new solutions and influencing authorities.