Department of Architecture and Civil Engineering

Naomi Deering

Instagram" @futurepoodoctor

Naomi Deering

BEng Civil Engineering MA International Relations

Covered, unplanted sludge drying beds

2.7 billion people rely on onsite sanitation systems as the predominant form of dealing with human waste. Poor understanding of the risks involved in handling and disposing this waste untreated has resulted in much of the faecal sludge (FS) being disposed of into nearby drains, open ditches or water bodies. Such practice undermines the gains made through increased sanitation coverage as the pathogens contained in untreated FS cause illness such as diarrohea which results in the death of 750,000 children under five every year as well as decreasing productivity and increasing health costs. It is estimated that every $1 spent on improved sanitation delivers $5 in social and economic benefits.

Sanitation is important and containing the waste produced  is just one link in the chain, the FS must then be collected, transported and treated to then be disposed of safely or re-used as compost or soil conditioner. Given the unsuitablility of the traditionally accepted solution of piped sewerage and centralised wastewater treatment works, new simpler, effective and lower cost solutions whic don't affect existing toilet technology is necessary. One of those solutions is covered,  unplanted drying beds whereby the FS is emptied onto a sand filter, and dries by drainage and evaporation, during which process the temperature within the sludge increases to kill pathogens. Once dry it is then raked off the bed and co-composted to further increase the temperature and continue pathogen reduction.

The aim of the research is to produce a chart to enable prediction of sludge drying time based upon the sludge moisture content, relative humidity and outside temperature.