Hydrothermal carbonisation of primary sewage sludge was carried out using a batch reactor. The effect of temperature and reaction time on the characteristics of solid (hydrochar), liquid and gas products, and the conditions leading to optimal hydrochar characteristics were investigated. The amount of carbon retained in hydrochars decreased as temperature and time increased with carbon retentions of 64-77% at 140 and 160°C, and 50-62% at 180 and 200°C. Increasing temperature and treatment time increased the energy content of the hydrochar from 17 to 19 MJ/kg but reduced its energy yield from 88% to 68%. Maillard reaction products were identified in the liquid fractions following carbonisations at 180 and 200°C. Theoretical estimates of the methane yields resulting from the anaerobic digestion of the liquid by-products are also presented and optimal reaction conditions to maximise these identified.

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13Hydrothermal carbonisation (HTC) has the capability to convert wet biomass such as sewage 14 sludge to a lignite-like renewable solid fuel of high calorific value. However, to date 15 assessment of the energy efficiency of the HTC process has not been fully investigated. In 16 this work, mass and energy balances of semi-continuous HTC of faecal waste conducted at 17 200 o C and at a reaction time of 30 min are presented. This analysis is based on recovering 18 steam from the process as well energy from the solid fuel (hydrochar) and methane from 19 digestion of the liquid product. The effect of the feedstock solids content and the quantity of 20 feed on the mass and energy balance were investigated. The heat of reaction was measured at 21 200 o C for 4 h with the wet faecal sludge, and the higher heating value was determined for the 22 hydrochar. The results indicated that preheating the feed to 100 o C using heat recovered from 23 the process would significantly reduce the energy input to the reactor by about 59%, and 24 decreased the heat loss from the reactor by between 50-60%. For feedstocks containing 15-25 25% solids (for all feed rates), after the process is in operation, energy recycled from the 26 flashing off of steam and combustion of the hydrochar and would be sufficient for preheating 27 the feed, operating the reactor and drying the wet hydrochar without the need for any external 28

Drinking water quality of surface and underground water within 1.34 km from a waste landfill site in Kumasi, Ghana was investigated. Physico‐chemical properties and heavy metal concentrations were analysed to determine water quality and pollution indices. It was found that turbidity of 83% of hand dug wells, 50% of the streams and 33% of boreholes were higher than World Health Organisation (WHO) standards for drinking water. Water quality index (WQI) showed that 25% of the water sources are of excellent quality, while 50%, 15% and 5% are good quality, poor quality, very poor quality and unsuitable for drinking, respectively. Heavy metal pollution index (HPI) indicated that the water sources were above the critical limit for drinking water (HPI > 100). Principal component analysis (PCA) revealed 75.30% and 70.88% of the total variance for the physico‐chemical parameters and heavy metals, respectively. The findings concluded that cadmium concentrations in all the water sources were extremely higher (0.0122–0.1090 mg/L) than WHO limit (0.003 mg/L), rendering them unwholesome for consumption.

a b s t r ac tThe hydrothermal carbonisation (HTC) conversion of wet wastes, such as sewage sludge, generates a carbon-rich material (called 'hydrochar'), and an aqueous fraction with a small release of gas. The liquid fraction is high in soluble chemical oxygen demand, from 10 to 50 g/L, and could not be discharged to the natural environment without treatment. This study investigates the anaerobic digestibility of this HTC liquid stream from different HTC temperatures and retention times (140°C-200°C for 30-240 min). It is focused on biogas production in order to improve the energy input of the HTC process and to improve process sustainability. The results demonstrated that liquid products from the lower HTC temperatures gave better biogas production. The biogas yield from the 140°C HTC filtrate digestion was 0.