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Abstract: Sequencing batch reactors (SBR) are widely used for wastewater treatment. The use of granular biomass in SBR allows higher organic loading rates (OLR). Nevertheless, the main disadvantage of SBR reactors is the presence of suspended solids in the effluent. In this study, effluents from a flocculent biomass SBR (F-SBR) and a granular biomass SBR (G-SBR) were treated in tertiary membrane filtration chambers to remove suspended solids. The performances of the operating systems were compared to determine the influence of the state of the biomass on the filtration process. No significant differences were observed between the two tertiary filtration systems in terms of capacity and permeability. Tertiary filtration of the effluent from the G-SBR was similar to that of the F-SBR system. The incorporation of wastewater free of suspended solids during one of the operating stages significantly worsened operation of the tertiary membrane filtration systems; permeabilities decreased by up to 40% in both systems. Additionally, other factors such as nitrification, the presence of soluble microbial products and the concentration of dissolved organic carbon seem to play an important role in tertiary membrane filtration. [Copyright &y& Elsevier]

Abstract: A nitrifying activated sludge unit operated in stable conditions was subjected to different instability actuations as overloads due to a sudden increase of the inlet ammonia concentration or a quick change of the inflow rate, pH shocks and limitations of dissolved oxygen (DO) concentration. The response of the unit to these different actuations was evaluated. During concentration overloads there were transitory nitrite accumulations but not during hydraulic overloads. However, efficiencies obtained for both kinds of overloads with respect to ammonia oxidation were very similar. The normal efficiency of the system was always restored and biomass was not washed out in spite of the low values of hydraulic retention time (HRT) used. The pH shocks of 9 and 10 had no appreciable effects, but the pH shock of 11 caused an irreversible loss of efficiency of 60%. An increase of the total organic carbon (TOC) in the effluent after this shock showed that biomass underwent a partial lysis. The specific activity of ammonia-oxidizers decreased from 0.6 to 0.3g NH4 +-N/(gVSSday) but the nitrite-oxidizing specific activity remained practically constant. Finally, the unit was operated at different DO levels, ammonia being fully oxidized to nitrate at DO levels higher than 1mg O2/L. Different proportions of ammonia and nitrite appeared when the reactor was operated at DO values of 0.4 and 0.6mgO2/L. [Copyright &y& Elsevier]

Focuses on a titrimetric method for monitoring toxicity in suspended biomass in order to measure the activity of nitrifying biofilms and to determine the effect of several toxic compounds on the biofilm. Details of study with respect to toxicity of tannery compounds on biofilms; Results suggesting an acceptable repeatability of the method for all the toxicants tested; Comparison of biofilm systems resistance to the toxicants, when the results obtained using suspended nitrifying biomass, with those found in the literature.

Abstract: The start-up of an Anammox process was studied in a membrane sequencing batch reactor (MSBR) in which a submerged hollow fibre membrane module was used to retain the biomass. The reactor was seed with Anammox biomass and fed using the Van de Graaf medium. During a first operating stage, salt precipitation was observed and interfered with microbial activity and caused a decrease of the nitrogen removal rate of the reactor from 100 to only 10mgl−1 per day. Salt precipitation was avoided by diminishing adequately the Ca and P concentrations of the Van de Graaf medium during the last operating stage. This action increased quickly the activity of the system, and nitrogen removal rate reached up to 710mgl−1 per day with almost full nitrite removal. Sporadic flotation of the sludge was observed in the MSBR. The use of the membrane avoided biomass wash-out from the system. Moreover, a surprising fact was that Anammox biomass did not grow in flocs in the MSBR, but in granules. This fact showed that this kind of microorganisms have a trend to grow in aggregates. Results indicated that the use of the MSBR could be a suitable system for nitrogen removal by using the Anammox reaction. [Copyright &y& Elsevier]

Abstract: A new pilot scale hybrid biofilm-suspended biomass membrane bioreactor was used to treat two wastewater streams generated in a fish canning factory. During a first stage, wastewater generated during tuna cooking with brine was treated. COD and N content were between 7.8–11.8 g COD/L and 1.2–1.8 g N/L, respectively. Salt concentration was up to 84 g/L. COD removal efficiency was affected by salinity, but after 73 operating days adaptation of the sludge to the hypersaline conditions took place. COD efficiency of 92% was obtained after adaptation of the sludge to the salinity. During a second stage, wastewaters generated during tuna cooking by steam injection were treated. HRT was fixed at 5 d. Organic loading rate was up to 4 kg COD/m3 d. COD concentration in the permeate was lower than 100 mg/L throughout this period. Salt concentration below 15 g/L did not affect nitrification. NLR was gradually increased up to 0.7 kg N/m3 d. Total nitrogen concentration in the permeate was lower than 100 mg N/L, and nitrate was below 65 mg N/L during the whole experimental period. Moreover, very low nitrate concentrations of less than 1 mg N/L were observed during the period in which a NLR up to 0.55 kg N/m3 d was applied. [Copyright &y& Elsevier]