bbk 000000

UDC 628.336

Koulakov A. A., Terekhova E. M., Kutsevol M. A.

Improvement of municipal wastewater sludge treatment methods

Summary

The introduction of the process schemes of removing nitrogen and phosphorus from wastewater demands a customized approach to handling the generated sludge. Permanent residence of sludge during thickening in anoxic conditions results in its septicity, deterioration of dewatering properties and phosphorus yield into supernatant. The results of the study of possible enhancement of municipal wastewater sludge thickening processes through the example of the Vologda wastewater treatment facilities that use nitrification-denitrification and biological dephosphorization in wastewater treatment are presented. During sludge dewatering in belt filter presses two return flows are generated – filtrate and washwater. Filtrate contains residual flocculant that can be reused. It was found that adding 10–15% filtrate from the dewatering facilities to the sludge during thickening resulted in increasing the thickening rate within first 30 minutes of the process, in particular; this fact provides for almost double reduction of the sludge amount. It is noted that 3 hours preaeration of sludge during thickening reduces the time of thickening by increasing the settling rate from 0.8 to 1.2–1.4 mm/min. A process flow scheme of sludge processing that includes two-stage thickening with preaeration and filtrate dosing and subsequent mechanical dewatering has been developed. Combining preaeration and filtrate dosing provides for reducing the sludge thickening time to 3–6 hours; improving its dewatering properties and reducing the dosage of flocculant during dewatering.

Key words

filtrate , activated sludge , compaction , wastewater sludges , dephosphatization , preaeration