Robust Decentralised Low Energy Faecal Sludge Dewatering leading to Sanitation, Clean Water and Sustainable Energy Resource

The project concerns dewatering/treatment of faecal sludge (black waters). Natural Synergies Ltd's (NS) aims are to develop a stand-alone dewatering process for rural areas of the UK/EU, reducing transport costs and carbon footprint and in developing countries as a low cost decentralised/localised sanitation system. The developed system can be also be used as a pre/post-cursor to a small scale anaerobic digestion (a follow-on proposal) or thermal unit, leading to closed loop decentralised, localised sanitation and off-grid energy generation. The dewatering process being developed will incorporate ultrasound to make available free, interstitial and cell water, together with electrokinetics to drive/separate water from faecal sludge via filter mesh. Preliminary work has shown potential for high levels of dewatering (15 - >40 % DM) and pathogen reduction (incl. helminths) at low energy inputs. System design will aim at non-specialised component manufacture, where possible, using local industries.
Our vision is to develop an entire new system of treating pit latrine wastes in developing countries, which not only generates renewable energy, but also a safe, useable fertilizer. In theory, this could be achieved now using conventional process technology. What is lacking, however, is a small scale robust system at relatively lower cost that can be operated with ease in remote areas. Our research contribution to delivering this is focussing on two specific challenges: Firstly, how to destroy human parasitic worms or their eggs, so as to allow safe reuse of the solidified material for agricultural fertilizer; Secondly, can we use locally available plant material to simultaneously increase the amount of energy, as biogas, which can be produced. The systems that Natural Synergies Ltd have been developing are highly effective but also highly innovative. We need to be sure of the overall environmental performance and social benefits of any new system, as well as its cost effectiveness. If successful this technology could also offer significant cost-savings and environmental benefits in developed countries at small-scale wastewater treatment plants in remote locations (e.g. Scottish Highlands), reducing road-tanker traffic, transport fuels and carbon emissions.

This research is primarily directed towards developing a technology which will have positive impacts on human health and the environment in developing countries. The commercial viability or efficiency of the technology is a pre-requisite to widespread implementation, so economic impacts are also a secondary priority.
The following groups might benefit from this research:
(1) NGOs providing effective local sanitation infrastructure in developing countries as part of overseas aid and or official development assistance
(2) Developing countries without access to grid electricity, biogas, refrigeration, with agricultural productivity limited by soil fertility and cost of fertilizer
(3) Water companies in developed countries attempting to simultaneously improve treatment standards while reducing cost and carbon footprint at isolated small PE waste water treatment sites.
(4) Developed countries committed to reducing fossil fuel use from manufacture of agricultural fertilisers and greenhouse gas emissions from transport of residual materials used for agricultural benefit

These possible benefits will be achieved in the following ways:
(A) Through more effective elimination of human health pathogens in small-scale, cost-effective local treatment plants in developing countries
(B) By adding renewable energy and useable fertilizer to the health benefits achievable from small-scale sewage-treatment plants in developing countries or crisis zones or areas receiving overseas aid
(C) By reducing the total volume of sludge transported from rural sewage treatment works in developed countries
(D) By earlier capture of biogas and so increasing the recovery rate of the renewable energy potentially available in sewage treatment
(E) By reducing the unnecessary water transported with nutrients in biosolids destined for land application, from 99.6-97% to 60-85% water content by mass, corresponding to a 5- to 100-fold increase in dry matter content (and hence an equivalent reduction in sludge volume)