Pilot-scale anaerobic submerged membrane bioreactor (AnSMBR) treating municipal wastewater: the fouling phenomenon and long-term operation.

An anaerobic submerged membrane bioreactor (AnSMBR) on pilot-scale treating a mixture composed of municipal wastewater and glucose under mesophilic temperature conditions was operated for 206 days. The performance of the AnSMBR was evaluated at different fluxes, biomass concentrations and gas sparging velocities (GSV). GSV was used to control fouling. In addition, the AnSMBR was operated in cycles that included relaxation and backwashing phases. The increase in the transmembrane pressure (fouling rate) was measured under different operational conditions and was used to evaluate the stability of the process. The fouling rate could be controlled for a long period of time at a flux of 7 l m(-2) h(-1) with a GSV of 62 m/h and an average biomass concentration of 14.8 g TSS/L. The membrane was physically cleaned after 156 days of operation. The cleaning efficiency was almost 100% indicating that no irreversible fouling was developed inside the pores of the membrane. The COD removal efficiency was close to 90%. As in anaerobic processes, nutrients were not exposed to degradation and almost no pathogens were found in the effluent, hence the effluent could be used for irrigation in agriculture.

Treatment of fatty solid waste from the meat industry in an anaerobic sequencing batch reactor: start-up period and establishment of the design criteria.

An anaerobic sequencing batch reactor (AnSBR) was used to treat the dissolved air flotation skimmings from a cooked pork meat plant. During the start-up period, the reactor was operated in fed-batch mode for 25 days and 7 batches were treated. The SBR was inoculated with sludge taken from a reactor treating distillery vinasse. The results showed that this kind of sludge is a very good source of inoculum for digesters treating residues with a high content in fats and long-chain fatty acids because it was able to adapt very rapidly to the new substrate and, from the second batch on, the sludge was already able to metabolize the fatty residue at quite high rates. The AnSBR was then operated with 5 batches per week for 110 days and the quantity of VS added per batch was regularly increased until the maximum treatment capacity of the reactor (i.e. maximum loading rate) was reached. The maximum organic loading rates were found to be 0.16 g VS/g VSS d, or 0.224 g VS/g VSS.batch when the reactor is fed 5 times a week. The biodegradability of the skimmings was very high, with more than 97% of TS removal, and the methane production was 880+/-90 mL of methane/g of VS(added).

Anaerobic digestion of gelatinous water at laboratory and pilot scale and nitrogen inhibition.

The anaerobic digestion of the liquid residue (gelatinous water) coming from the production of fat from animal residue, was studied at laboratory and pilot scale. Biodegradability (>98%) and biogas potential (675 mL of biogas/g of COD(applied)) of this wastewater are very high. However, due to the high content on nitrogen, an inhibition of the anaerobic activity was observed for quite low concentrations of N-NH(3). Dilution of the wastewater and pH regulation in the reactor around 7.3 are the 2 solutions which were investigated to overcome the nitrogen inhibition at industrial scale. These two solutions were validated at laboratory scale in an anaerobic SBR and then onsite at pilot scale in a continuous reactor. A stable anaerobic digestion was observed in both reactors showing that no nitrogen inhibition was obtained when N-NH(3) concentration in the reactor was kept low.