Application of Municipal Sewage Sludge Ash for Waste-activatedSludge Thickening and Dewatering: a Comparative Study

In this study, the feasibility and efficiency of using sewage sludge ash (SSA) as a conditioner for wasteactivatedsludge and anaerobic stabilized sludge thickening and dewatering was investigated in a lab-scale.Also, the employing of SSA as an alternative coagulant along with organic and inorganic conditioners wasevaluated based on the results of lab-scale tests. In this regard, the main factors effectiveness, including thesludge pH value and the injection dosage of conditioner on indices such as sludge volume index (SVI), time tofilter (TTF), and specific resistance to filtration (SRF) were surveyed. Based on the results, the highest rate ofSRF decrement and TTF reduction occurred at the pH value of ۳ and SSA dosage of ۰.۲۵ g/g DS for wasteactivatedsludge. While, SSA did not have an acceptable effect on anaerobic stabilized sludge dewatering.Nevertheless, the obtained results from the review of SVI index indicated the poor and inappropriateperformance of SSA for waste-activated sludge thickening. The findings of simultaneous application of SSAwith cationic poly-electrolyte showed no significant improvement in the dewatering efficiency, while the usageof SSA along with ferric chloride indicated that SSA is a suitable alternative for lime in combination with ferricchloride. Finally, it can be concluded that sewage sludge ash has a potential to ameliorate the waste-activatedsludge dewatering alone or as an effective alternative coagulant instead of lime besides ferric chloride, resultingin a reduction of the chemicals consumption.

کلیدواژه ها:

Sludge treatment ، Waste-activated sludge thickening and dewatering ، Conditioning ، Sewagesludge ash