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The physico-chemical characteristics of the sludge samples of the 30 pit latrines are shown in Table 1. Levene's test for homogeneity of variance revealed a significant variation between the 30 samples analysed, considering the physico-chemical parameters tested. Regarding the pH, the minimum value measured was 5.9, attaining a maximum of 8.9 with a median of 7.2, showing that the pit latrine sludge pH studied is slightly basic. Samples also exhibited a high solids content with a median value of 44.8% of DM. Medians for EC and salinity were, respectively, 4.8 mS/cm and 2.4‰.

Table 1

Descriptive statistics of the physico-chemical parameters of sludge samples (n = 30)

Sludge parameterspHEC (mS/cm)Salinity (‰)COD (g O2/L)BOD5 (g O2/L)NH4+ (g/L)TKN (g/L)DM (%)Moisture content (%)
Minimum 5.9 0.2 0.1 0.4 0.1 0.01 0.04 32.7 44.4 
Maximum 8.9 17.2 10.1 124.2 18.5 2.5 4.9 55.5 67.3 
Median 7.2 4.8 2.4 34.0 3.2 0.3 1.7 44.8 55.2 
Std deviation 0.8 3.8 2.5 34.1 4.2 0.6 1.6 6.3 6.3 
Percentile 25 6.74 3.3 0.7 14.2 2.1 0.2 0.9 38.5 52.5 
75 7.9 8.9 4.7 58.2 7.7 1.2 3.5 47.7 61.9 
Kengne et al. (2008)  6.5–9.3   30.5  0.4 0.9 2.9  
Heinss et al. (1998)     20–50  2–5  ≥3.5  
Bassan et al. (2013)     12.4 2.1     
Sludge parameterspHEC (mS/cm)Salinity (‰)COD (g O2/L)BOD5 (g O2/L)NH4+ (g/L)TKN (g/L)DM (%)Moisture content (%)
Minimum 5.9 0.2 0.1 0.4 0.1 0.01 0.04 32.7 44.4 
Maximum 8.9 17.2 10.1 124.2 18.5 2.5 4.9 55.5 67.3 
Median 7.2 4.8 2.4 34.0 3.2 0.3 1.7 44.8 55.2 
Std deviation 0.8 3.8 2.5 34.1 4.2 0.6 1.6 6.3 6.3 
Percentile 25 6.74 3.3 0.7 14.2 2.1 0.2 0.9 38.5 52.5 
75 7.9 8.9 4.7 58.2 7.7 1.2 3.5 47.7 61.9 
Kengne et al. (2008)  6.5–9.3   30.5  0.4 0.9 2.9  
Heinss et al. (1998)     20–50  2–5  ≥3.5  
Bassan et al. (2013)     12.4 2.1     

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