A Comprehensive Study on the Physicochemical Characteristics of Faecal Sludge in Greater Accra Region and Analysis of Its Potential Use as Feedstock for Green Energy

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.

Variability of faecal sludge characteristics and its implication for dewaterability across different on-site sanitation containments in unplanned settlements in Dar es Salaam, Tanzania

“…Knowing FS physical-chemical characteristics while still in containment can contribute towards a better understanding of the future design criteria and appropriate selection of FS treatment technologies. Despite numerous studies on FS characteristics (Niwagaba et al 2014;Ahmed et al 2019;Awere et al 2020), the variability of physical-chemical characteristics of FS affected by the type of OSS containments and season has not been documented based on type. Moreover, the physical-chemical predictor of FS also varies with season.…”

Analysis of Soil Quality Status and Accumulation of Potentially Toxic Element in Food Crops Growing at Fecal Sludge Dumpsite in Ubakala, Nigeria

“…The concentration of potentially toxic element in dried fecal sludge is summarized in (Chen et al, 2003) (Table 2). The concentration of Zn (12.41±0.30 mg/kg) from fecal sludge dumpsite at Ubakala, Nigeria is higher than 0.058 to 0.094 mg/kg in fecal sludge at Accra region of Ghana (Ahmed et al, 2019). The concentration of Cd in the dried fecal sample was 0.07±0.00 mg/kg, which is well below the accepted limits of 5 mg/kg and 3 mg/kg set by China (GB 4284-1984 andGB 4284-2018), respectively, 20-40 mg/kg (Cd) by the European Union (Directive 86/278/EEC) and 2 mg/kg (Cd) in Sweden (Chen et al, 2003) (Table 2).…”

Toilet chemical additives and their effect on faecal sludge characteristics

“…The BOD 5 and COD values could be partly because the sludge was fresh and largely undigested. This is possible because it was confirmed during sampling that the public toilets were desludged between 1 and 3 weeks, therefore organic loads could only be partially degraded or not [ 25 ]. Meanwhile, the biodegradability ratio (BOD 5 /COD) ratio was around 0.3, a low value indicating that the sludge is largely composed of slowly degradable substances [ 29 ].…”

“…One of the key challenges faced by managers of these public sanitation facilities is cost burden associated with the management of faecal sludge generated. The toilet facilities receive high usage rates [ 24 ], with quickly filled up pits and always requiring frequent desludging incurring higher cost [ 3 , 22 , 23 , 25 ]. The challenging situation was same for the only functional toilets from which faecal sludge samples were taken at the time of the study.…”