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UBC Theses and Dissertations

Sidestream control of dissolved nutrients in anaerobically digested sludge centrate using anammox and chemical precipitation Galvagno, Giampiero


The objective of this research was to assess specific side-stream processes for biodegradation and precipitation of dissolved nutrients in dewatering centrate and support the seamless integration of an anaerobic digester (AD) into a biological nutrient removal wastewater treatment plant (WWTP). Anaerobic digestion processes release reactive and non-reactive dissolved nutrients which are returned to the mainstream treatment process in the dewatering centrate. Conventional side-stream treatment processes are typically designed for removal of reactive nutrients (ie, nitrate/nitrite, ammonia and orthophosphate). However, many WWTPs with low total nitrogen and total phosphorus criteria will also be impacted by the non-reactive, difficult-to-degrade nutrient forms such as polyphosphates (poly-P), dissolved organic phosphorus (DOP) and dissolved organic nitrogen (DON). In this study, characterization was made of a conventional suspended growth deammonification treatment (Anammox) process for transforming poly-P, DOP and DON in two types of dewatering centrate. The first centrate feed studied was from the full-scale Annacis Island WWTP (AIWWTP), Canada. The second centrate feed was from a lab-scale AD fed waste sludge from the existing City of Kelowna Wastewater Treatment Facility (KWTF), Canada. The Anammox process showed similar treatment characteristics for both the KWTF and AIWWTP centrates with excellent DON removal and poor non-reactive dissolved phosphorus (NRDP) removal. A statistical comparison of the DOP and poly-P through the Anammox process suggests that DOP has a higher biodegradation potential. Utilization of a post-Anammox, poly aluminum chloride chemical dosing, optimized based on zeta potential, was able to achieve the objective of precipitating residual DON and NRDP and producing an effluent with lower dissolved nutrients than the pre-digestion KWTF dewatering centrate scenario. Additional testing was conducted on final effluent to characterize the dissolved phosphorus and determine an optimal coagulant dose. The testing suggests that the dissolved phosphorus in effluent could be associated with colloidal dissolved organic matter (DOM). Furthermore, coagulant batch dosing experiments using poly aluminium chloride (PACL) and poly epichlorohydrin amine (polyepiamine) provides strong support for the use of zeta potential measurements as a way to optimize coagulant dose.

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