Abstract
Design of treatment plants for faecal sludge management systems relies on a comprehensive accurate knowledge of FS (faecal sludge) characteristics, but this information is lacking. Developing countries like Ghana, where large proportion of the urban population (Accra) rely on onsite sanitation systems, face a lot of FSM (faecal sludge management) design challenges as a result of lack of a comprehensive study data on physicochemical characteristics of raw faecal sludge after primary dewatering. Achieving a fully operational FSM chain would imply a well understanding of the characteristics of the FS and its dynamics after primary dewatering. A study was carried out to determine the characteristics of faecal sludge brought to the Lavender Hill treatment plant, Accra Metropolis, and environs to ensure the treatability and uses of the products after treatment. The treatment plant receives an average of 150 trucks (1350m3) a day with 58% coming from private homes and 42% from public toilets. Composite samples were made from both public and private toilets facilities. Samples were taken from a reservoir holding faecal sludge from both public and private facilities, examined on daily basis and characterized. The values obtained showed high concentrations of BOD and COD values. The COD: BOD ratios showed that the faecal sludge is not stabilized yet and can be further degraded. The calorific value for the dry sludge was found to be 15.16-15.82 MJ/kg and 16.39–18.31 MJ/kg for the wet sludge. The calorific value of the sludge is adequate enough to be used as potential feedstock for green energy generation. The high concentrations of COD and organic matter of the faecal sludge make it suitable enough for biogas generation. A good correlation (r=0.909,R2=82.6%) between the calorific value and the TVS was found to be CV=0.122TVS+7.44. Heavy metal concentrations were low and satisfied the EPA Ghana guidelines for sludge. Thus products from the treatment can be used for agricultural purposes.
Highlights
Faecal sludge management (FSM) has not been given the needed attention for the past decades in Africa [1, 2] making FSM difficult and cumbersome for states to manage [3,4,5] and Greater Accra Region of Ghana is not in exception
The analysis indicated that the FS is of “low strength” for the domestic source samples; this is consistent with the works of Bassan, Heinss, and Koottatep [1, 42, 43]
This study presents for the first time comprehensive insight into the understanding of the raw faecal sludge and its potential utility in composting and feedstock for green energy
Summary
Faecal sludge management (FSM) has not been given the needed attention for the past decades in Africa [1, 2] making FSM difficult and cumbersome for states to manage [3,4,5] and Greater Accra Region of Ghana is not in exception. Accra and other urban areas in Ghana are often faced with poor sanitation situation [3, 6] leading to faecal sludge management crises [3]. It is estimated that one-third of the world’s population, approximately 2.4 billion urban dwellers, rely on onsite sanitation system (OSS) installations such as public latrines, aqua privies, and septic tanks [8]. Faecal sludge (FS) generated in Ghana and many developing countries is mainly made up of public toilet sludge (PTS) and septage [8] which are disposed of untreated and indiscriminately into lanes, drainage ditches, and open urban spaces [3, 4, 6, 9,10,11,12]. The process involved in FSM in Ghana within the context of FSM chain is fourfold: collection, transportation, disposal, and treatment
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