Long term performance of a pilot scale anaerobic membrane bioreactor treating beet molasses based industrial wastewater.

Baker's yeast industries (BYI) generate highly polluted effluents, especially vinasse from yeast separators, with very high chemical oxygen demand (COD), nitrogen, sulphate and salts, mainly potassium and calcium. Anaerobic treatment is the most commonly applied method for treating BYI wastewaters. However, it is quite challenging to obtain a high performance due to the difficulties in biomass retention. Moreover, it does not provide compliance with COD and color discharge limits when used as a sole treatment process. In this context, a pilot scale anaerobic membrane bioreactor, which provides excellent biomass retention, was operated to investigate its treatment performance for vinasse from a BYI. The reactor achieved a COD removal between 48% and 92% up to a volumetric load of 10 kg COD m3 d-1. A specific methane production of 0.37 m3 CH4 kg-1 CODremoved was observed in the study. On the other hand, passage of inert organic compounds through membrane deteriorated permeate quality and treatment efficiency. High alkalinity and pH led to the accumulation of calcium precipitates, which reduced volatile solids fraction of sludge and biomass activity in the reactor. The present study showed the operational challenges and potential drawbacks of AnMBR systems for BYI wastewater treatment. The experience gained in the pilot system can be utilized in the design and operation of full scale AnMBRs for high strength industrial effluents.

Demand response through reject water scheduling in water resource recovery facilities: A demonstration with BSM2.

The objective of this paper is to determine the importance of integrating peak demand mitigation and future energy pricing structures for process modelling of conventional water resource recovery facilities (WRRFs) when evaluating energy cost and control strategies. The well-established benchmark simulation model (BSM2) is used to monitor energy usage, and a detailed holistic study of different flow streams is performed in order to establish potential opportunities for flexible control of WRRF energy demand. Secondly, a detailed framework is introduced to optimize scheduling control strategies for the reject water stream while considering peak electricity demand avoidance as well as completing a comprehensive energy cost model based on current and anticipated future energy tariff structures. The reject water scheduling strategies, without other active controls (e.g. aeration), revealed 63.4% average peak demand mitigation and €10,755 cumulative annual energy cost savings on a 100k population equivalent WRRF without a deterioration in effluent quality. Analysis of different reject water scheduling control strategies shows that reject water scheduling can be an effective tool for energy cost optimisation under alternative electricity tariff structures. These strategies also deliver electricity peak demand mitigation.

Effect of sludge retention time on the biological performance of anaerobic membrane bioreactors treating corn-to-ethanol thin stillage with high lipid content.

The potential of anaerobic membrane bioreactors (AnMBRs) for the treatment of lipid rich corn-to-ethanol thin stillage was investigated at three different sludge retention times (SRT), i.e. 20, 30 and 50 days. The membrane assisted biomass retention in AnMBRs provided an excellent solution to sludge washout problems reported for the treatment of lipid rich wastewaters by granular sludge bed reactors. The AnMBRs achieved high COD removal efficiencies up to 99% and excellent effluent quality. Although higher organic loading rates (OLRs) up to 8.0 kg COD m(-3) d(-1) could be applied to the reactors operated at shorter SRTs, better biological degradation efficiencies, i.e. up to 83%, was achieved at increased SRTs. Severe long chain fatty acid (LCFA) inhibition was observed at 50 days SRT, possibly caused by the extensive dissolution of LCFA in the reactor broth, inhibiting the methanogenic biomass. Physicochemical mechanisms such as precipitation with divalent cations and adsorption on the sludge played an important role in the occurrence of LCFA removal, conversion, and inhibition.