Assessment of dry and wet fenton sludge reusability in treating palm oil mill secondary effluent and toxicity level on Cyprinus carpio Linnaeus

Biological treatment which is commonly adopted in palm oil mill wastewater treatment has contributed to massive sludge production. Thus, Solar Fenton Oxidation was proposed as a tertiary treatment since the sludge produced from the treatment contained iron which can be reused. Therefore, this study aims to assess the feasibility of wet and dry Fenton sludge as iron sources in Solar Fenton Oxidation treatment and determine the toxicity against Cyprinus carpio Linnaeus. Results showed the mean reading of COD, colour, BOD, turbidity and TSS for untreated POMSE are 3507mg/L, 4959ADMI, 260mg/L, 2867mg/L and 1744mg/L respectively, which exceeded the standard limit set by DOE and EQA. Compared to dry Fenton sludge, wet Fenton sludge exhibit soft and watery texture with 91.9% moisture, while dry Fenton sludge is hard, soil like and 0% moisture. Both have a specific gravity of 2.4- 2.5. The TSS, VSS and VSS% for the wet Fenton sludge are 4050mg/L, 2760mg/L and 68.15% while 0% for the dry Fenton sludge. The optimum condition obtained for pH, H2O2/COD, and Fe/COD were 3, 1.59 and 1.0 respectively. The usage of recycle wet and dry Fenton sludge are significant only for COD removal in R1, R2 and R3 (pvalue0.05). The toxicity test showed that most of the effluent treated with recycle wet and dry Fenton sludge were less toxic compared to untreated POMSE. In conclusion, it is justifiable to reuse the Fenton sludge in Solar Fenton Oxidation as iron sources. However, further research is required to determine the possible toxic component in POMSE and Solar Fenton Oxidation treated effluent to ensure the safety of aquatic life.