Abstract
This study investigated the chemical and thermal properties of faecal sludge from 10 dry VIP latrines in Bester's Camp in the eThekwini Municipality, Durban, South Africa. Faecal sludge samples were selected at different depths and from the front and back sections of 10 VIP latrines during a manual emptying process. The samples were analysed for: moisture content; volatile solids; chemical oxygen demand; ammonia; total Kjeldahl nitrogen; pH; orthophosphate; thermal conductivity; calorific value and heat capacity. These properties will facilitate the design of faecal sludge emptying and treatment equipment. A manual sorting of the pit contents was carried out to determine the categories and amounts of household waste present. There was a significant difference in the moisture, volatile solids, chemical oxygen demand, ammonia, total Kjeldahl nitrogen and orthophosphate content of the faecal sludge between the front and back sections of the pit. There was minimal change in the thermal properties within the pit. The median values through the pit of each property analysed were: moisture content - 0.81 g water/g wet mass; volatile solids - 1.5 g VS/g ash; COD - 1.7 g COD/g ash; ammonia nitrogen - 10 mg NH3-N/g dry mass; TKN - 39 mg N/g dry mass; pH - 8.03; orthophosphate - 0.06 mg PO4/g dry mass; thermal conductivity - 0.55 W/m K; calorific value - 14 kJ/g dry mass; heat capacity - 2.4x103 kJ/kg K. On average, 87% of pit content is faecal sludge; the remainder consists of wastes such as paper, plastics and textiles.
Highlights
In South Africa, 31.3% of households have their sanitation needs met by a pit latrine; 12.5% are ventilated improved pit (VIP) latrines while 18.8% are pit latrines without ventilation (Statistics SA, 2011)
The second study, by Wood (2013), analysed for a wider selection of properties for samples collected at 4 depths of 2 VIP latrines – these tests included pH, alkalinity, moisture content, volatile solids, chemical oxygen demand (COD), biodegradable COD, total Kjeldahl nitrogen (TKN), ammonia, total phosphorus and orthophosphate, in order to model the degradation processes in a pit and to obtain a baseline understanding of the chemical transformations in the VIP
A student t-test was conducted to determine if the faecal sludge property in one part of the pit was significantly different to the same property in another section of the pit
Summary
In South Africa, 31.3% of households have their sanitation needs met by a pit latrine; 12.5% are ventilated improved pit (VIP) latrines while 18.8% are pit latrines without ventilation (Statistics SA, 2011). The processes occurring in a VIP are: filling (with faecal matter, water and other material); water transfer in and out of the pit; biological transformation; and pathogen deactivation (Buckley et al, 2008) These processes affect the properties of the faecal sludge within the pit. The second study, by Wood (2013), analysed for a wider selection of properties for samples collected at 4 depths of 2 VIP latrines – these tests included pH, alkalinity, moisture content, volatile solids, COD, biodegradable COD, total Kjeldahl nitrogen (TKN), ammonia, total phosphorus and orthophosphate, in order to model the degradation processes in a pit and to obtain a baseline understanding of the chemical transformations in the VIP.
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