Investigation of direct waste‐activated sludge dewatering benefits and costs in a water resource recovery facility. (19th October 2021)

• Record Type: Journal Article
• Authors: Mentzer, Casey; Drinkwater, Michael; Pagilla, Krishna R.
• Is Part Of: Water environment research. Volume 93:Number 12(2021)
• Page Start: 2998
• Page End: 3010
• Publication Date: 2021-10-19
• Subjects: decreased chemical use -- direct WAS dewatering -- enhanced biological phosphorus removal -- reduced nutrient recycles -- struvite; Water quality management -- Periodicals; Water -- Purification -- Periodicals; Water -- Pollution -- Periodicals; Water -- Pollution; Water -- Purification; Water quality management; Sewage; Water Pollution; Periodicals; Electronic journals; Periodicals; 628.16
• DOI: 10.1002/wer.1651
• Languages: English
• ISSNs: 1061-4303

Abstract

Abstract: Dewatering of anaerobic digested (AD) sludge containing waste‐activated sludge (WAS) from enhanced biological phosphorus removal (EBPR) poses numerous challenges including poor dewaterability, struvite scale formation, and recycling of high N and P levels in the sludge liquor to the treatment process. A full‐scale water reclamation facility was investigated to mitigate these problems by experimenting with direct dewatering of EBPR WAS, bypassing the AD step. The investigations experimented with various blends of AD primary sludge with undigested thickened WAS to achieve dewatering performance improvements and overall operational cost savings. Direct thickened WAS dewatering has had many positive impacts including enhanced sludge cake solids concentration, reduced chemical use for facility operations, reduced struvite scaling, reduced biogas conditioning media servicing, eliminated need for centrate treatment, recovered capacity of existing unit operations including anaerobic digesters, and eliminated several proposed capital improvement projects that were previously deemed necessary. Although bypassing of WAS to AD reduced total biogas production, the specific gas yield increased to meet all of the facility's biogas demands and minimized excess gas flaring. The overall biosolids production mass increased causing increased transportation costs for disposal and caused notable odors, both of which are being currently investigated. Practitioner Points: Direct WAS dewatering bypassing anaerobic digestion yields operational and process benefits in an EBPR water resource recovery facility Dewatered cake solids were increased compared with combined primary and WAS anaerobic digestion and dewatering Nutrient loads in sludge processing returns streams and operational costs are reduced by direct WAS dewatering Abstract : Two modes of waste activated sludge (WAS) treatment was investigated. Blending of thickened WAS with primary sludge prior to digestion (status quo) was compared with direct thickened WAS dewatering bypassing digestion. Direct thickened WAS dewatering was operationally better than the status‐quo.