Reuse of Water-Treatment-Plant Sludge Coagulants for Reusing in Water and Wastewater Treatment

This study focused to investigate the effectiveness of recycled iron sludge (RIS)
coagulants for reuse in treating various wastewater streams. Leachate from Kelantan
landfill, river water and petroleum refinery waste were being used in for this study to
evaluate the effectiveness of the recycled iron sludge (RIS). Parameters such as pH,
turbidity, and chemical oxygen demand (COD) were evaluated. For leachate treatment,
RIS coagulant is comparable to alum to treat leachate, with a slight removal of COD at
36% for alum and 8% for RIS. However, it is crucial to evaluate the pH since this metal
coagulant is acidic andthe coagulant addition mayconsume alkalinity andresults in very
acidic treated samples. Addition of 1mLof RIScoagulant into watersample removed the
turbidity to 95%. When the dosage was further increased to 60 mL, the removal increased
slightly to 97%o. It is also found that the optimal dosage of RIS for petroleum refinery
wastewater treatment was 114.74 mg/L, with the final pH of 10.8. The second phase of
the project was focused on only petroleum refinery waste where a series of jar test was
conducted to obtain the optimumdosage pH for alum and RIS, which were found to be 9
and 10 respectively. Without adjusting the pH, the petroleum refinery waste treatment
using RIS as a coagulant showed that 20 mg/L of RIS removed 95% of COD. The test
was repeated with pH adjustment to 10, and it is showed 120 mg/L were needed to
remove 97% ofCOD with the final pH of 7.6.