Novel approach to improving wastewater treatment and sewage sludge combustion using pulverized coal-activated sludge

Abstract

Sewage and sludge are usually treated separately. Considering improving sludge treatment while improving sewage treatment is beneficial to the synergetic effect of sewage treatment and sludge treatment. The efficiency of pulverized coal-activated sludge (PAS) on contaminant removal, sludge calorific value, and combustion characteristic was investigated in contrast to conventional activated sludge (CAS) using the laboratory-scale sequencing batch reactor (SBR). Results indicated that the average chemical oxygen demand, ammonium nitrogen, total nitrogen, and total phosphorus removal efficiency of PAS were highest under a dosage of 0.4 g/L, which were 98.56%, 94.22%, 68.60%, and 95.96%, respectively. The average effluent concentration satisfied the Level A discharge standard of pollutants for municipal wastewater treatment plants (GB18918-2002). The calorific value and maximum weight loss of PAS gradually increased adjusting the dosage of pulverized coal. At the pulverized coal dosage of 0.2 g/L, the calorific value of PAS with 70% water content is 3,824.07 kJ/kg, which can satisfy the requirement of self-maintained combustion. Overall, the pulverized coal can simultaneously improve the treatment of wastewater in SBR and promote the sludge combustion by increasing calorific value. Therefore, PAS system is an innovation based on improving the sewage treatment sludge combustion. PRACTITIONER POINTS: An innovative method to simultaneously improving wastewater treatment and sewage sludge combustion using pulverized coal-activated sludge was developed. The average COD, ${\text{NH}}_4^{+}-N$ , TN, and TP removal efficiency of PAS-0.4 is best. The 70% moisture content sludge calorific values of 3,824.07 kJ/kg in PAS-0.2 can satisfy the requirement of self-maintained combustion.

Keywords: pulverized coal-activated sludge; sequencing batch reactor; sludge combustion; wastewater treatment.