Inoculum-free start-up of biofilm- and sludge-based deammonification systems in pilot scale

摘要

Undiluted reject water from the dewatering of anaerobic sludge with an average total nitrogen content of 718 +/- 117 mg L-1 (n = 63) was used to start-up autotrophic nitrogen removal in three different pilot-scale (3 m(3)) deammonification configurations: (1) biofilm; (2) activated sludge sequence batch; and (3) two-staged (nitritation-anammox). Time- and concentration-based aeration control with alternating aerobic/anaerobic phases was applied for all reactor configurations. All reactors were initiated without anammox-specific inoculum, and biofilm was grown onto blank carriers. During the initial start-up period, biological nitrogen removal was found to be inhibited by an excessive free ammonia content ( 10 mg-N L-1), resulting from the use of high-strength reject water as the process feed. After implementation of free ammonia control by pH adjustment to 6.5-7.5, propagation of the deammonification process was observed with increased nitrogen removal with slight accumulation of NO3 (-)-N. The highest total nitrogen removal rates were achieved with the single-reactor biofilm- and sludge-based deammonification processes (1.04 and 0.30 kg-N m(-3) day(-1), respectively). The critical factors for successful start-up and stable operation of deammonification reactors turned out to be control of pH below 7.5, dissolved oxygen at 0.3-0.8 mg-O-2 L-1 and influent solids values below 1000 nephelometric turbidity units. Microbial analysis demonstrated that highest anammox enrichment was achieved in the biofilm reactor (9.40 x 10(8) copies g(-1) total suspended solids). These data demonstrate the potential of an in-situ grown sludge- or biofilm-based concept for the development and propagation of deammonification process.