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Mathematical modelling was used to investigate the possibility to use membrane aerated biofilm reactors (MABRs) in a largely anoxic suspended growth bioreactor to produce the nitrate-nitrogen required for heterotrophic denitrification and the growth of denitrifying phosphorus accumulating organisms (DPAOs). The results indicate that such a process can be used to achieve a variety of process objectives. The capture of influent biodegradable organic matter while also achieving significant total inorganic nitrogen (TIN) removal can be achieved with or without use of primary treatment by operation at a relatively short suspended growth solids residence time (SRT). Low effluent TIN concentrations can also be achieved, irrespective of the influent wastewater chemical oxygen demand (COD)/total nitrogen (TN) ratio, with somewhat larger suspended growth SRT. Biological phosphorus and nitrogen removal can also be effectively achieved. Further experimental work is needed to confirm these modelling results. HIGHLIGHTS Hybrid MABRs can achieve lower effluent TIN concentrations, and more carbon capture, at lower SRTs than conventional systems.; Influent carbon composition affects denitrification, but modelling shows better performance in hybrid MABR systems.; Primary treatment benefits carbon capture, but can be eliminated depending on treatment goals.; Combined biological nitrogen and phosphorus removal is possible and improved in hybrid MABRs.

This paper shows the potential application of a new sewage treatment process with technologies of excess sludge reduction and phosphorus recovery. The process incorporated ozonation for excess sludge reduction and crystallisation process for phosphorus recovery to a conventional anaerobic/oxic (A/O) phosphorus removal process. A lab-scale continuous operation experiment was conducted with the ratio of sludge flow rate to ozonation tank of 1.1% of sewage inflow under 30 to 40 mgO3/gSS of ozone consumption and with sludge wasting ratio of 0.34% (one-fifth of a conventional A/O process). Throughout the operational experiment, a 60% reduction of excess sludge production was achieved in the new process. A biomass concentration of 2,300 mg/L was maintained, and the accumulation of inactive biomass was not observed. The new process was estimated to give a phosphorus recovery degree of more than 70% as an advantage of excess sludge reduction. The slight increase in effluent COD was observed, but the process performance was maintained at a satisfactory level. These facts demonstrate an effectiveness of the new process for excess sludge reduction as well as for phosphorus recovery.

This investigation aims to monitor a strategy for biological nutrient removal (nitrogen and phosphorus) in a Sequencing Batch Reactor (SBR) treating domestic wastewater. For this, the performance of an SBR with nitrification, denitrification, carbon oxidation and phosphorus removal is evaluated. During this study the influent used was pre-settled domestic wastewater from Bennekom-Municipal Treatment Plant (The Netherlands). The average influent COD, TKN and phosphate were 443 mg COD/1, 71 mg N/1 and 7 mg P/1, respectively. Acetic acid was added to this influent from a feed solution, to increase the COD by an extra 100 mg COD/1. In this study, a pilot plant SBR was operated during 5 months in order to have: i) a mixed culture able to perform carbon oxidation, nitrification, denitrification and biological phosphorus removal and ii) long term assessment of the biological nitrogen and phosphorus removal processes. Pilot plant SBR consists of two cylindric polystyrene vessels, the first with total volume of 0.35 m3 (Reactor 1) and the second with total volume of 1.3 m3 (Reactor 2). The effluent had, in average, phosphate concentration lower than 1 mg P/1 and nitrogen concentration lower than 12 mg N/1.

Experimental work was carried out with a lab-scale SBR, whose operation was divided into three runs: I run (glucose + acetate feed, 3′ fill), II run (only glucose feed, 3′ fill), III run (only glucose feed, 60′ fill). The results show that the bacteria growing in alternating anaerobic/aerobic systems can remove organic substrates under anaerobic conditions even without using the hydrolysis of polyphosphates or the transformation of glycogen into poly-hydroxyalkanoates as the energy sources for the uptake and storage of substrate. However, in the case of acetate plus glucose feed, EBPR can be steadily established with typical PP-bacteria like metabolism even if most of the COD removal takes place under not truly anaerobic conditions.

Some of the advantages of on-line automatic measurement of ammonia, nitrate and phosphate for studying activated sludge systems are pointed out with the help of examples of batch experiments. Sample taking is performed by cross-flow filtration and measurement of all three analytes is performed by Flow Injection Analysis (FIA). Two batch set-ups are described. In the first, one of the two 800 1 nitrifying/denitrifying tanks of a pilot-scale alternating process is employed as batch reactor, which has the advantage of a high measurement frequency and little preparatory and clean-up effort. The second consists of four 5 1 jars connected to the FIA system and allows on-line measurement of ammonia, nitrate and phosphate while performing batch reactions in parallel. Each of the four examples described was designed to study a particular aspect pertaining to Enhanced Biological Phosphate Removal (EBPR): the effect of acetate addition on aerobic P-uptake; the recovery of aerobic P-uptake after a disturbance; the interaction between denitrification and P-release when acetate is added at various rates; and the effect of stored PHB levels on denitrification by phosphate accumulating organisms.