Abstract:
It is estimated that 61 % and 29 % of the global population lack safely managed
sanitation and clean water services respectively. The water Sustainable Development
Goals (SDG 6) actioned by the UN, aim to provide global access to sanitation and clean
water by 2030. However, in low income countries (LICs) conventional centralised
wastewater treatment plants are economically unfeasible and for affordable
decentralised alternatives, only 22 % of the waste is safely managed, leading to
contamination of water resources. The Reinvent the Toilet Challenge (RTTC) initiated
by the Bill & Melinda Gates Foundation (BGMF) proposes to innovate off-grid, self-
sustaining systems, which are able to safely manage human waste and provide
opportunity for resource recovery, at ≤US$0.05 user⁻¹ d⁻¹. In response, the Nano
Membrane Toilet (NMT) developed at Cranfield University propositions a household
scale sanitation system which combusts human faeces and provides an off-grid
opportunity for advanced treatment technologies to treat the liquid fraction, comprising
faecally contaminated urine (FCU). This thesis investigated a series of potential
separation processes which integrate with the combustor, for FCU treatment.
It was demonstrated that solids liquid separation can be facilitated post flush
with a screw auger, which allowed for effective faecal solids recovery for the
combustor. Thermally driven membrane processes, which operate from heat energy,
evidenced that high water quality where reuse standards could be achieved (with
operational optimisation) in a single stage. In addition, they proved robust to faecal
contamination and manipulated odour profiles to change negative perception. The most
adaptable process, membrane distillation (MD), provided a salinity gradient consisting
of a concentrated retentate and deionised permeate where salinity gradient energy was
converted to electrical energy through reverse electrodialysis (RED), sufficient to power
an auxiliary low voltage fluidic device (0.25 W) for 4.9 hours. Importantly, the
integrated separation processes within this thesis, evidenced high quality water and
energy recovery, which are the foundations of an SDG 6 solution.
