The performance of UASBCD and UASBASDIT reactors at different temperatures varying between 17 and 38 C and sludge age ranging from 60 to 180 days is shown in Table 4.
There is an increase in the efficiency of the reactors with an increase in the temperature and sludge age. At a temperature of 17 C and a sludge age of 60 days, COD removal efficiency of UASBCD and UASBASDIT reactors was 62 and 57%, respectively.
Whereas TSS removal efficiency of these reactors at the same temperature and sludge age was 44 and 41%, respectively.
However, their BOD5 removal efficiency was slightly better (66% and 61%, respectively). Low removal efficiency under psychrophilic conditions (17 C) and early sludge age may be attributed to incomplete sludge granulation and insufficient volume of settled solids and biomass, which consequently reduced the methanogenic activity of sludge microorganism and slowed down the hydrolysis and substrate consumption rate