Pilot-scale enrichment of anammox biofilm using secondary effluent as source water.

Runxian Tao,Mai Li,Yongli Sun,Fansong Wu,Min Yang,Xingcan Zheng,Xingfang Guo,Shifeng Shen

doi:10.2166/wst.2021.015

Abstract

Enough biomass of anaerobic ammonium oxidation (anammox) bacteria is essential for maintaining a stable partial nitrification/anammox (PN/A) wastewater treatment system. Present enrichment procedures are mainly labor-intensive and inconvenient for up-scaling. A simplified procedure was developed for enrichment of anammox biofilm by using secondary effluent as source water with no supplement of mineral medium and unstrict control of influent dissolved oxygen (DO). Anammox biofilm was successfully enriched in two pilot-scale reactors (XQ-cul and BT-cul) within 250 and 120 days, respectively. The specific anammox activity increased rapidly during the last 2 months in both reactors and achieved 2.54 g N2-N/(m2·d) in XQ-cul and 1.61 g N2-N/(m2·d) in BT-cul. Similar microbial diversity and community structure were obtained in the two reactors despite different secondary effluent being applied from two wastewater treatment plants. Anaerobic ammonium oxidizing bacteria genera abundance reached up to 37.4% and 43.1% in XQ-cul and BT-cul biofilm, respectively. Candidatus Brocadia and Ca. Kuenenia dominated the enriched biofilm. A negligible adverse effect of residual organics and influent DO was observed by using secondary effluent as source water. This anammox biofilm enrichment procedure could facilitate the inoculation and/or bio-augmentation of large-scale mainstream PN/A reactors.

Highlights

Partial nitritation/anammox (PN/A) is an attractive autotrophic nitrogen removal technology for the merits of energy-saving and no need for carbon sources
The PN/A process has been successfully applied in the treatment of sludge liquor, landfill leachate, and other ammonium-rich wastewater (Van der Star et al ; Joss et al ; Lackner et al )
Most mainstream PN/A reactors were inoculated at the start-up period and/or bio-augmented during operation with enriched anammox biomass in the form of granular sludge or carriers-supported biofilm (Lotti et al ; Gilbert et al ; Wett et al )

Summary

Introduction

Partial nitritation/anammox (PN/A) is an attractive autotrophic nitrogen removal technology for the merits of energy-saving and no need for carbon sources. In-situ cultivation and enrichment of anammox bacteria in mainstream conditions is difficult and time consuming due to their sensitivity to operational conditions and slow growth rate with a typical doubling time of about 11 days (Strous et al ; Van der Star et al ). For this reason, most mainstream PN/A reactors were inoculated at the start-up period and/or bio-augmented during operation with enriched anammox biomass in the form of granular sludge or carriers-supported biofilm (Lotti et al ; Gilbert et al ; Wett et al ). It is a necessity to find a practicable enrichment procedure for accumulating enough anammox biomass to promote the establishment of an up-scaling mainstream PN/A system and reduce start-up time, especially if there is no available side-stream system for inoculation

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