Reinvent The Toilet Presented by Prof. Andrew Wheatley at FWR / CIWEM John Street, London on Thursday 1 st November 2012
Familiar Numbers Approaching 50% urbanisation. Worldwide, 2.5 billion people are without a toilet. 1 billion without safe drinking water. Embedded water. Business opportunity is immense.
Gates Criteria No grids. Safe. No Smell, noise, touch. Easy to use (developing countries). Affordable. Secondary users.
More out of waste Biorefinery EU Supergen initiative UK Supported by the Research Councils Midlands Universities Sustainable energy consortium Birmingham,Nottingham Loughborough Sunday, 20 January 2013
Heat Recovery Gas Separation & Purification Methane Hydrogen Supercritical Water Gasification & Partial Oxidation Recovery of Valuable Minerals Phosphate Nitrogen Other Inorganic's + Water Mixed Cellulosic Biomass Mechanical & Thermal pretreatment Anoxic Bioreactor for Hydrolysis Anaerobic Bioreactor Autotrophic Bioreactor Methane Hydrogen CO 2 Thermal Hydrolysis Separation (Filtration & Ion Exchange) Residual Cellulose & Detoxified Hydrolysate Sugar-rich Hydrolysate Catalytic Reactions Furanic Biofuels Furanic Di- Carboxyllic Acids
Interdisciplinary team Developing Countries M Sohail Khan Materials Simon Martin Chemical Engineering Richard Holdich Water Engineering Andrew Wheatley Researchers Julia Zakharova Eric Danso-Boateng Health Ergonomics and Design Diane Gyi
Thermal Treatment Hazardous and polluting No infrastructure recovery of valuable materials, sterilised.
Published Energy Values in Wastewater and Sludges WERF (2011) Wastewater Solids Mj/kg COD MJm 3 MJ/kg DS Primary sludge @ 430 mg/l = 13.5 5.8 15.0 Biomass sludge 13.0 Eckhoff and Wood RITC (2011) 4.0 Shizas and Bagley Toronto (2004) Heodroch,Curtis and Dolfing Newcastle Industrial Domestic @ 431 mg/l = 14.7 6.3 3.2 Oven dry @ 718 mg/l = 22.5-28.7 8.3 5.9 Freeze dry @ 576.2 mg/l = 17.7 16.8 10.5 Oven dry 5.6 5.1 Freeze dry 17.8 7.6 6.9
Faeces and Primary Sludge Characteristics Faeces, % * Primary sludge, % ** Fats 5 25 Fibres 10 30 Nitrogenous material 2 3 Minerals (K, Ca and P) 5 8 Bacterial debris 10 30 * Source: Niwagaba et al., 2007 Fats 18 26 Fibres 5 12 Mineral content 15 25 Proteins 15 21 Total nitrogen 3.2 3.8 Phosphorus 1.4 2.5 ** Source: Yakovlev and Voronov (2002)
Organics in Wastewaters Mean values, g/l This study (4hrs) Ramke et al. (2009) 12 hrs Simulant faeces Primary sludge Mixed organics COD 33.6 37.6 15 62 TOC 5.53 7.27 10 18 Berge et al. 2011 Food Wastes
The Process Flow Sheet
Why Hydrothermal Controlled lower temperatures than direct heating. No drying. Already wet 5-8% DS Captured VOC.
Method Standard synthetic faeces were pressurised to 3 bar, (standard autoclave 120 0 C and 1.5 bar)then heated in batch (140 C, 160 C, 180 C and 200 C). The reaction was then run for different times to collect reaction rate or kinetic data. Mass loss ratio was measured together with observations on carbonisation. the first sample was taken as soon as the mixture reached the desired temperature but then run for variable times according to the carbonisation observed.
140 C Timeline of photos 50mins 20mins 80mins 140mins 260min 380mins Maximum pressure = 7.5bar (Saturated pressure=2.6bar). None of the experiments carbonised. Some products became slightly darker. Product cannot be filtered. From 2 hours, water could be separated off as clear layers in the collecting vessel.
20mins Timeline of photos 80mins 160 C 50mins 140min 260mins 320mins 380mins Maximum pressure = 12bar (Saturated pressure = 5.2bar). Product carbonised after 6 hours. Some products became slightly darker. Carbonised product was easily filterable.
180 C 30mins 60mins 90mins 150min 270mins Maximum pressure = 16bar (Saturated pressure = 9bar). Product fully carbonised from 2 hours. Much darker after 30minutes, with black flecks starting to appear (initial stages of carbonisation).
200 C 40mins 70mins 100min 160min 280min Maximum pressure = 20bar (Saturated pressure = 14.5bar). All products carbonised. Slightly greater mass loss at longer times.
ln(m/m[0]) Civil and Building Engineering 200 C 0 Heating time = 50minutes 0 50 100 150 200 250 300 350-0.2-0.4-0.6 1 st carbonised point This experiment had a leak of pressure, but it could be seen that all other points followed the line of best fit well enough that a repeat was not needed -0.8-1 Gradient = 0.0128-1.2-1.4 Time (minutes)
Summary of experiments to design carbonization conditions Ln (k)
Water Content Experiments were run at 180 C with an initial moisture content of 75% instead of 95%. It was expected for these to carbonise more easily, as the faeces particles were a pellet rather than dispersed in the liquid. Two process times, either side of the carbonisation limit, were tested (30mins, 1hr, 2hr and 4hr). This had no effect on the product, showing there is no need for mechanical handling before processing 180C for 4 hours 5% ds 25% ds
Citric acid catalyst A full set of results was collected at 180 C with a citric acid catalyst. Carbonising after the same amount of time and very similar mass losses. With catalyst No catalyst 180C for 2 hours With catalyst No catalyst 180C for 1 hour
Solids Losses Synthetic 140 o C Pressure Cooker Time min. Mass % 0 0 20 2 50 4 80 6 140 8 260 12 380 15 170 o C Superheated Time min. Mass % 0 0 20 9 30 18 50 22 60 23 80 29 90 38 100 44 150 47 270 52 280 50 380 51
Impact of solid losses on drainage water Solids, % TOC/10, g/l 100 Primary Sludge Solids filt, % TOC/10, g/l 100 Simulant Faeces 80 60 Screened solids % TOC/10, g/l 80 60 Screened solids % TOC/10, g/l 40 40 20 0 100 200 300 20 0 100 200 300 Time, min Time, min
Ammonia in drainage water 1000 Ammonia, mg/l 800 600 400 200 Simulant faeces Primary sludge 0 0 100 200 Time, min The protein content in sludge is greater
The Laboratory scale Unit Continuous hydrothermal carbonisation
Conclusions Reaction time at 160 C would be 6 hours, at 180 C 2 hours. 140 C does not carbonise, even after 12 hours. It has been shown that no mechanical handling is needed before processing or after. Fibre and Rheology improved. The process water contains > 35 g/l COD and > 6 g/l TOC (10-20%)potentially equal amount in the condensate.
Further research Critical particle size requirements fibres, clogging. Mass balances heat, solids, nitrogen and VOC. More valuable by products. Waste treatment with / without grid connections the biorefinery concept other wastes. Scale up, real environments and new materials.
Heat Recovery Gas Separation & Purification Methane Hydrogen Supercritical Water Gasification & Partial Oxidation Recovery of Valuable Minerals Phosphate Nitrogen Other Inorganic's + Water Mixed Cellulosic Biomass Mechanical & Thermal pretreatment Anoxic Bioreactor for Hydrolysis Anaerobic Bioreactor Autotrophic Bioreactor Methane Hydrogen CO 2 Thermal Hydrolysis Separation (Filtration & Ion Exchange) Residual Cellulose & Detoxified Hydrolysate Sugar-rich Hydrolysate Catalytic Reactions Furanic Biofuels Furanic Di- Carboxyllic Acids
Block Diagram for treatment of solids and liquids from Reinvented Toilet 40mins 100mins Components 70mins Partial separation 160mins Hydrothermal reactor Decompression Final separation 280mins Liquids Salt removal ( as appropriate)