Integrated side-stream reactor for biological nutrient removal and minimization of sludge production

Integrated processes to reduce in situ the sludge production in wastewater treatment plants are gaining attention in order to facilitate excess sludge management. In contrast to post-treatments, such as anaerobic digestion which is placed between the activated sludge system and dewatering processes, integrated technologies are placed in the sludge return line. This study evaluates the application of an anoxic side-stream reactor (SSR) which creates a physiological shock and uncouples the biomass metabolism and diverts the activity from assimilation for biosynthesis to non-growth activities. The effect of this system in biological nutrient removal for both nitrogen and phosphorus was evaluated for the anaerobic, anoxic and aerobic reactors. The RedOx potential within the SSR was maintained at -150 mV while the sludge loading rate was modified by increasing the percentage of recycled activated sludge feed to the SSR (0 and 40% at laboratory scale and 0, 10, 50 and 100% at pilot scale). The use of the SSR presented a slight reduction of phosphorus removal but maintained the effluent quality to the required discharge values. Nitrogen removal efficiency increased from 75 to 86% while reducing the sludge production rate by 18.3%

Response to high nitrite concentrations of anammox biomass from two SBR fed on synthetic wastewater and landfill leachate

The present work aimed to assess nitrite inhibition on granular anammox biomasses and to verify the following recovering ability. The granular biomass used came from two lab-scale sequencing batch reactors (SBRs) treating synthetic wastewater (SBR-1) and real landfill leachate (SBR-2), with similar nitrogen removal efficiencies (around 85–90%). The specific anammox activity (SAA) was determined by manometric batch tests where different concentrations of nitrite _100 to 500 mg NO2-N/L and exposure times (3–4 h, 24 h) were applied. The biomass from both reactors was consisted of Brocadia enrichments and presented similar behavior under high nitrite exposure, in spite of being adapted to very different matrix of wastewater. Anammox granules from both reactors were proven to be quite tolerant to moderate to high nitrite shocks, as long as the exposure time was limited to 3–4 h (less than 40% activity loss at 500 mg NO2—N/L). The activity loss was substantial after prolonged exposure (24 h) and the IC50 (half maximal inhibitory concentration) for SBR-1 and SBR-2 granules was set at 173 +/-23 mg NO2—N/L and 171 +/- 8mg NO2—N/L, respectively. The biomass recovered the activity with values up to 60–80% of the initial maximum SAA immediately after washing to remove the nitrite

Simultaneous domestic wastewater treatment and renewable energy production using microbial fuel cells (MFCs)

Microbial fuel cells (MFCs) can be used in wastewater treatment and to simultaneously produce electricity (renewable energy). MFC technology has already been applied successfully in lab-scale studies to treat domestic wastewater, focussing on organic matter removal and energy production. However, domestic wastewater also contains nitrogen that needs to be treated before being discharged. The goal of this paper is to assess simultaneous domestic wastewater treatment and energy production using an air-cathode MFC, paying special attention to nitrogen compound transformations. An air-cathode MFC was designed and run treating 1.39 L d(-1) of wastewater with an organic load rate of 7.2 kg COD m(-3) d(-1) (80% removal efficiency) and producing 1.42 W m(-3). In terms of nitrogen transformations, the study demonstrates that two different processes took place in the MFC: physical-chemical and biological. Nitrogen loss was observed increasing in line with the power produced. A low level of oxygen was present in the anodic compartment, and ammonium was oxidised to nitrite and nitrate

Effect of cycle changes on simultaneous biological nutrient removal in a sequencing batch reactor (SBR)

The destabilization of a microbial population is sometimes hard to solve when different biological reactions are coupled in the same reactor as in sequencing batch reactors (SBRs). This paper will try to guide through practical experiences the recovery of simultaneous nitrogen and phosphorus removal in an SBR after increasing the demand of wastewater treatment by taking advantage of its flexibility. The results demonstrate that the length of phases and the optimization of influent distribution are key factors in stabilizing the system for long-term periods with high nutrient removal (88%, 93% and 99% of carbon, nitrogen and phosphorus, respectively). In order to recover a biological nutrient removal (BNR) system, different interactions such as simultaneous nitrification and denitrification and also phosphorus removal must be taken into account. As a general conclusion, it can be stated there is no such thing as a perfect SBR operation, and that much will depend on the state of the BNR system. Hence, the SBR operating strategy must be based on a dynamic cycle definition in line with process efficiency

Combining partial nitritation and heterotrophic denitritation for the treatment of landfill leachate previous to an anammox reactor

Landfill leachate can present extremely elevated concentrations of ammonium (up to 6,000 mg N-NH(4)(+)L(-1)) and a low biodegradable organic matter fraction. As an alternative to conventional systems, this wastewater can be treated on a more sustainable way by a fully autotrophic partial nitritation-anammox system. The operation of the first step of this system, the partial nitritation, is critical since the elevated concentrations of ammonium and nitrite in the reactor can severely inhibit ammonium oxidizing bacteria (AOB) activity. In this way, the inclusion of anoxic phases during the feeding events to promote the denitrification via nitrite can be a good option for upgrading the process performance and increasing the stability of the system. This paper deals with the evaluation of an anoxic-aerobic step-feed strategy for the operation of a partial nitritation SBR. Results of this study have revealed a decrease on the total nitrogen inside the reactor of more than 200 mg NL(-1) without prejudice on the partial nitritation process. Furthermore, this study has also allowed detecting an AOB activity reduction at the end of aerobic phases due to bicarbonate limitation and/or free nitrous acid inhibition