Feasibility of a return-sludge nursery concept for mainstream anammox biostimulation: Creating optimal conditions for anammox to recover and grow in a parallel tank

• DOI: 10.1016/j.biortech.2023.129359
• Publication Date: 2023-06-19T06:10:02Z
• Authors: Weiqiang Zhu; Michiel Van Tendeloo; Abbas Alloul; Siegfried E. Vlae...
• Keywords: Anammox; Biostimulation; Mainstream

To overcome limiting anammox activity under sewage treatment conditions, a return-sludge nursery concept is proposed. This concept involves blending sludge reject water treated with partial nitritation with mainstream effluent to increase the temperature, N levels, and electrical conductivity (EC) of the anammox nursery reactor, which sludge periodically passes through the return sludge line of the mainstream system. Various nursery frequencies were tested in two 2.5 L reactors, including 0.5-2 days of nursery treatment per 3.5-14 days of the total operation. Bioreactor experiments showed that nursery increased nitrogen removal rates during mainstream operation by 33-38%. The increased anammox activity can be partly (35-60%) explained by higher temperatures. Elevated EC, higher nitrogen concentrations, and a putative synergy and/or unknown factor were responsible for 15-16%, 12-14%, and 10-36%, respectively. A relatively stable microbial community was observed, dominated by a "Candidatus Brocadia" member. This new concept boosted activity and sludge growth, which may facilitate mainstream anammox implementations based on partial nitritation/anammox or partial nitrification/denitratation/anammox.