Boris Lesjean

Process configurations adapted to membrane bioreactors for enhanced biological phosphorous and nitrogen removal

Abstract Enhanced biological phosphorous (Bio-P) removal process was adapted to membrane bioreactor (MBR). One bench-scale pilot plant (BSP, 200–250 L) and two medium-scale pilot plants (2//MSP, 1000–3000 L each) were operated under several configurations, including pre-denitrification and post-denitrification without addition of carbon source, and two solid retention times (SRT) of 15 and 26 d, in parallel to the full-scale Bio-P removal activated sludge plant of Berlin-Ruhleben (12–18 d SRT). The trials showed that efficient Bio-P removal can be achieved with MBR systems, in both pre- and post-denitrification configurations. Bio-P dynamics could be clearly demonstrated through batch-tests, on-line measurements, profile analyses, P-spiking trials, and mass balances. High P-removal performances were achieved even with high SRT of 26 d (around 9 mgP/L was removed with P/TS∼2.6%). Under similar operation conditions of sludge age and mass organic load, the MBR system achieved slightly higher P-removal than the conventional technology. This was due to the rejection of particles and colloids through the microfiltration membrane. When spiking with phosphate, high Bio-Premoval of up to 35–40 mg/L could be achieved without addition of external carbon source, and P/TS stabilized around 7.5%.

Impacts of membrane flux enhancers on activated sludge respiration and nutrient removal in MBRs

This paper presents the findings of experimental investigations regarding the influence of 13 different flux enhancing chemicals (FeCl3, polyaluminium chloride, 2 chitosans, 5 synthetic polymers, 2 starches and 2 activated carbons) on respirometric characteristics and nitrification/denitrification performance of membrane bioreactor (MBR) mixed liquor. Flux enhancing chemicals are a promising method to reduce the detrimental effects of fouling phenomena via the modification of mixed liquor characteristics. However, potentially inhibiting effects of these chemicals on mixed liquor biological activity triggered the biokinetic studies (in jar tests) conducted in this work. The tested polyaluminium chloride (PACl) strongly impacted on nitrification (-16%) and denitrification rate (-43%). The biodegradable nature of chitosan was striking in endogenous and exogenous tests. Considering the relatively high costs of this chemical, an application for wastewater treatment does thus not seem to be advisable. Also, addition of one of the tested activated carbons strongly impacted on the oxygen uptake rate (-28%), nitrification (-90%) and denitrification rate (-43%), due to a decrease of pH. Results show that the changes in kLa values were mostly not significant, however, a decrease of 13% in oxygen transfer was found for sludge treated with PACl.

Design criteria for semi-central sanitation with low pressure network and membrane bioreactor-the ENREM project

MBR-technology is able to fulfil similar or even higher standard for nutrients removal than conventional activated sludge processes. This paper presents the optimisation of the membrane bioreactor technology, together with a low pressure sewer, to equip a remote and yet unsewered area of Berlin requiring high quality wastewater treatment. The hydraulic flow pattern of the entire system has to be studied carefully due to the small collection system (no time delay between wastewater discharge and treatment to minimise the daily profile). The pollutant concentrations in the wastewater exhibit also stronger variations. In order to flatten out the hydraulic and load profile, and therefore to reduce the size of the biological reactor and the membrane surface, a buffer tank was installed before the MBR-plant. A full analysis of the influent hydraulic flow and wastewater characterisation is provided for the demonstration MBR-plant.

MBR: Technology gets timely EU cash boost

Four international projects subsidised by the European Commission should push forward the development and application of membrane bioreactor processes in the municipal wastewater sector.