Impact of solids retention time on the biological performance of an AnMBR treating lipid-rich synthetic dairy wastewater (original) (raw)
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Treatment of dairy wastewater with a membrane bioreactor
Brazilian Journal of Chemical Engineering, 2013
Among the food industries, the dairy industry is considered to be the most polluting one because of the large volume of wastewater generated and its high organic load. In this study, an aerobic membrane bioreactor (MBR) was used for the treatment of wastewater from a large dairy industry and two hydraulic retention times (HRT), 6 and 8 hours, were evaluated. For both HRTs removal efficiencies of organic matter of 99% were obtained. Despite high permeate flux (27.5 L/h.m²), the system operated fairly stablely. The molecular weight distribution of feed, permeate and mixed liquor showed that only the low molecular weight fraction is efficiently degraded by biomass and that the membrane has an essential role in producing a permeate of excellent quality.
Separation and Purification Technology, 2015
In this study, the filtration performance of anaerobic membrane bioreactors when treating a high strength lipid rich wastewater, corn-to-ethanol thin stillage, is evaluated at different solids retention times (SRTs). Long chain fatty acid (LCFA) inhibition, observed at high SRTs, concomitantly occurred with floc deterioration and soluble microbial product release. On the other hand, accumulation of LCFA on the sludge modified its surface hydrophobicity. Remarkably, a lesser degree of fouling was observed at increased sludge hydrophobicity. Cake layer formation was found as the most important contributor to membrane filtration resistance, whereas chemical cleaning tests indicated a low degree of irreversible organic fouling. Moreover, inorganic fouling in the form of phosphorus precipitates was identified both in the cake layer and on the membrane.
Integrated anaerobic treatment of dairy industrial wastewater and sludge
Water Science & Technology, 2009
Performance parameters were studied in an alternative full-scale dairy effluent treatment system comprising two anaerobic sludge-blanket reactors in parallel arrangement with upward flow, internal fat-separation by flotation, external lamella settler and floated material digester. Reactors were initially inoculated with flocculent sludge and granulated in a high-load stage. Using loading rates up to a maximum 5.5 kgCOD/m 3 .d -hydraulic residence time of 17 hours-reactor efficiency was found to remain stable around 90% of COD. Average sludge digester efficiency using a loading rate of 3.5 kgVS/m 3 .d with a lipid content of 47% of COD amounted to 78% of VS (87% of lipid removal). LCFA inhibition as assayed using palmitate was found to depend not only on the palmitate concentration but also on the palmitate-to-biomass concentration ratio.
Water Research, 2005
A novel high-rate anaerobic reactor, called ''Buoyant Filter Bioreactor'' (BFBR), has been developed for treating lipid-rich complex wastewater. The BFBR is able to decouple the biomass and insoluble COD retention time from the hydraulic retention time by means of a granular filter bed made of buoyant polystyrene beads. Filter clogging is prevented by an automatic backwash driven by biogas release, which fluidizes the granular filter bed in a downward direction. During filter backwash, the solids captured in the filter are reintroduced into the reaction zone of the reactor. The reaction zone is provided with a mixing system, which is independent of the hydraulic retention time.
Internal versus external submerged membrane bioreactor configurations for dairy wastewater treatment
Desalination and Water Treatment, 2013
Two submerged membrane bioreactor (SMBR) configurations, one with the membrane module internal (SMBRi) and the other one external (SMBRe) to the biological tank, were used for the treatment of dairy industry effluent and evaluated in terms of pollutant removal capacity and fouling, focusing on the production of soluble microbial products (SMP) and extracellular polymeric substances (EPS). Both the MBRs presented excellent chemical oxygen demand (COD) removal efficiency (98% average), color (98%), and nutrients (86% for total nitrogen and 86-89% for total phosphorus); however, it was shown that shearing caused by the sludge recirculation pumps in the SMBRe reduced biomass growth considerably. The SMBRe presented better performance in terms of fouling than the SMBRi, which was associated with the higher concentration of suspended solids and SMP and EPS in the SMBRi. The SMP concentrations (mgSMP/gMLVSS) were superior in the SMBRe, showing that the friction from recirculation pumps leads to the breakdown of flocs and/or cells and to the release of polymeric material into the mixed liquor. Since this effect was more intense for SMP quantified in terms of extracellular transparent polymers, the conclusion was that apparently these substances participate in cellular metabolism in a different way than the carbohydrates and proteins, and that these can be more associated with released substances due to shear stress.
Biochemical Engineering Journal, 2011
The dairy industry is generally considered to be the largest source of food processing wastewater in many countries. The highly variable nature of dairy wastewaters in terms of volumes and flowrates and in terms of high organic materials contents such as COD 921-9004 mg L −1 , BOD 483-6080 mg L −1 , TN of 8-230 mg L −1 and SS of 134-804 mg L −1 makes the choice of an effective wastewater treatment regime difficult. A high performance bioreactor, an aerobic jet loop reactor, combined with a ceramic membrane filtration unit, was used to investigate its suitability for the treatment of the dairy processing wastewater. The oxygen transfer rates of the bioreactor were found to be very high (100-285 h −1) on the operating conditions. A loading rate of 53 kg COD m −3 d −1 resulted in 97-98% COD removal efficiencies under 3 h hydraulic retention time. The high MLSS concentrations could be retained in the system (up to 38,000 mg L −1) with the contribution of UF (ultrafiltration) unit. During the filtration of activated sludge, the fluxes decreased with increasing MLSS. Cake formation fouling was determined as dominant fouling mechanisms. The results demonstrate that jet loop membrane bioreactor system was a suitable and effective treatment choice for treating dairy industry wastewater.
Desalination, 2011
This study aimed at evaluating the effect of increasing organic loading rates and of enzyme pretreatment on the stability and efficiency of a hybrid upflow anaerobic sludge blanket reactor (UASBh) treating dairy effluent. The UASBh was submitted to the following average organic loading rates (OLR) 0.98 Kg.m −3 .d −1 , 4.58 Kg.m −3 .d −1 , 8.89 Kg.m −3 .d −1 and 15.73 Kg.m −3 .d −1 , and with the higher value, the reactor was fed with effluent with and without an enzymatic pretreatment to hydrolyze fats. The hydraulic detention time was 24 h, and the temperature was 30 ± 2°C. The reactor was equipped with a superior foam bed and showed good efficiency and stability until an OLR of 8.89 Kg.m −3 .d −1 . The foam bed was efficient for solid retention and residual volatile acid concentration consumption. The enzymatic pretreatment did not contribute to the process stability, propitiating loss in both biomass and system efficiency. Specific methanogenic activity tests indicated the presence of inhibition after the sludge had been submitted to the pretreated effluent. It was concluded that continuous exposure to the hydrolysis products or to the enzyme caused a dramatic drop in the efficiency and stability of the process, and the single exposure of the biomass to this condition did not inhibit methane formation.