Randy Perrera

On-farm Treatment Options for Wastewater, Greywater and Fecal Sludge

Fecal contamination  of  urban  and  peri-urban  water  bodies is  a  major  health  issue  in  most  low-  and  middle-income  countries,  where  population  growth  exceeds  the  rate  of  development  of  wastewater  or  fecal  sludge  collection  and  treatment infrastructure. While the  expansion  of  sewer  systems  and  treatment  capacity  remain  a  high  priority  for  municipal  authorities, there are opportunities for applying low-cost, small-scale on-farm options for safe recovery of wastewater and fecal sludge for reuse in forestry, horticulture, fodder and food production. These options can complement other risk reduction measures on farm, in markets and food kitchens as previously shown by IWMI.

On-farm treatment options are based on the same processes as those used in conventional wastewater treatment, such as sedimentation, flocculation,  filtration  and  natural  die-off.  The Resource Recovery and Reuse Report  Number 1 presents an overview of some low-cost wastewater treatment technologies for pathogen removal, which  can  be  adapted  for  use  in  urban  and  peri-urban  areas  in  low-income  countries where the wastewater is of domestic origin. Interventions  which  can  build  on  farmers’  current  practices,  such  as  on-farm  storage ponds or river bank filtration, will probably have the highest potential of acceptance.

Researchers from IWMI have identified three types of options have been highlighted. Information is provided on pathogen removal, use of systems in West African context and their recommendations for use:

1. On-farm treatment systems

Wastewater  treatment  ponds  are  one  of  the  best-known  treatment  systems  which  are  especially  suitable  for  low-income  countries  due  to  their  low  costs,  low  energy  and  maintenance  needs,  and  high  performance  based  on  ‘natural’ processes. Ponds  improve  water  quality  by  allowing  settlement  of  particles  and  pathogens  (sedimentation  process),  and  also exposing pathogens to the environment. Settlement  times  of  particles  and  pathogens  differ  depending  on their sizes and densities. Ponds can be combined to remove pathogens in one, while fetching water in the other.

2. Filtration Systems

Filtering polluted water is also a low-cost  option  taking  advantage  of  natural  processes  for  pathogen  elimination.  Compared  to  pond  systems  it  has  the  additional  advantage  of  working  even  at  the  smallest scale, such as for household water filtration. A number of options are explored here including retention by straining, organic filters, slow sand filters, river bank filtration and trench filter beds and constructed wetlands.

3. Farm-based Fecal sludge treatment

The application  of  excreta-based  fertilizers  has  attracted much attention as a concept of ecological sanitation and due to  increasing  fertilizer  prices.  Besides  its  nutrient  content,  fecal  sludge is  also  rich  in  organic  matter,  which  can  contribute   positively   to   soil   structure   and   water-holding   capacity.  Hence, fecal sludge  represents  an  important  resource  for enhancing  soil  productivity,  in  general. Options here highlight the use of raw fecal sludge collected by vacuum trucks from on-site sanitation systems which is regionally in  high  demand  by  farmers  growing  maize  and  sorghum  on poor savannah soils. While sanitizing fecal sludge through composting is the preferred option, also the application of raw fecal sludge is possible if certain precautions are taken.

These options were documented by IWMI researchers and arose out of various research projects in support of the  GlobE  -  UrbanFood Plus  project,  an  African-German partnership to enhance resource use efficiency and improve food  security  in  urban  and  peri-urban  agriculture  of  West African cities.

For more information and resources go to the UN Water Safe Use of Wastewater in Agriculture Site