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1

Investigation on biomass performance of a submerged membrane bioreactor for treating soy sauce wastewater

Lv S., Liang Z., Li X., Fan H., Zen Y.

Environment Protection Engineering

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2016

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Vol. 42, nr 1

135--148

EN

A pilot study for investigating a membrane bioreactor (MBR) performance in treating soy sauce wastewater was divided into three stages. At stage 1, the MBR was operated without excess sludge withdrawal, and pollutants removal increased gradually and entered into a pseudo-stable phase eventually along with increasing mixed liquor suspended solid (MLSS). At stage 2, the growth of biomass and removal of pollutants were obviously decreased by lowering temperature. At stage 3, membrane permeate flux and sludge yield under various MLSSs were studied. Additional polishing steps including coagulation and oxidation were validated to be effective to ensure the treated wastewater to meet the discharge limits.

2

Energy consumption in terms of shear stress for two types of membrane bioreactors used for municipal wastewater treatment processes

Ratkovich N., Bentzen T., Rasmussen M.

Archives of Thermodynamics

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2012

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Vol. 33, no. 2

85-106

EN

Two types of submerged membrane bioreactors (MBR): hollow fiber (HF) and hollow sheet (HS), have been studied and compared in terms of energy consumption and average shear stress over the membrane wall. The analysis of energy consumption was made using the correlation to determine the blower power and the blower power demand per unit of permeate volume. Results showed that for the system geometries considered, in terms the of the blower power, the HF MBR requires less power compared to HS MBR. However, in terms of blower power per unit of permeate volume, the HS MBR requires less energy. The analysis of shear stress over the membrane surface was made using computational fluid dynamics (CFD) modelling. Experimental measurements for the HF MBR were compared with the CFD model and an error less that 8% was obtained. For the HS MBR, experimental measurements of velocity profiles were made and an error of 11% was found. This work uses an empirical relationship to determine the shear stress based on the ratio of aeration blower power to tank volume. This relationship is used in bubble column reactors and it is extrapolate to determine shear stress on MBR systems. This relationship proved to be overestimated by 28% compared to experimental measurements and CFD results. Therefore, a corrective factor is included in the relationship in order to account for the membrane placed inside the bioreactor.

3

DGGE-based monitoring of bacterial diversity in activated sludge dealing with wastewater contaminated by organic petroleum compounds

Ziembińska A., Ciesielski S., Wiszniowski J.

Archives of Environmental Protection

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2010

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Vol. 36, no. 4

119-125

EN

Polycyclic aromatic hydrocarbons (PAHs) belong to the group of recalcitrants that on reaching wastewater can irreversibly inhibit some sensitive biological processes in activated sludge such as nitrification. This situation leads to wastewater treatment failure due to the influence of these substances on bacteria responsible for important biochemical processes. Observation of the changes in bacterial diversity using molecular tools, such as denaturing gradient gel electrophoresis (DGGE), could be the first step in finding a way of preventing wastewater treatment failure. The aim of this experiment was to monitor bacterial biodiversity in a membrane bioreactor (MBR) dealing with synthetic wastewater contaminated with high concentration of petroleum organic compounds (POCs) and to study the influence of POCs contamination on bacterial changeability in activated sludge. COD removal in investigated membrane bioreactors was at a level of 93%. The organics removal efficiency was not affected by the maximal tested dose of petroleum contamination (1000 μl POCs/l of wastewater) and the MBRs wastewater treatment performance was undisturbed. DGGE analysis revealed that the biodiversity fluctuated slightly in control MBR, while in experimental MBR the biodiversity index decreased drastically after adding the highest experimental concentration of POCs. These results suggest that concentrations of POCs at levels from 50 μl/l to 500 μl/l stimulate biodiversity growth, while the concentration 1000 μl POCs/l of wastewater seems to inhibit the most sensitive processes in wastewater treatment by influencing the bacterial biocenosis.

PL

Substancje ropopochodne należą do grupy zanieczyszczeń, które, docierając do oczyszczalni ścieków, mogą zaburzać wrażliwe procesy biochemiczne, takie jak nitryfikacja. Taka sytuacja prowadzi do problemów z oczyszczaniem ścieków, ponieważ substancje te mogą wpływać na bakterie odpowiedzialne za podstawowe procesy biochemiczne. Obserwacja zmian różnorodności bakteryjnej w osadzie czynnym za pomocą narzędzi biologii molekularnej, takich jak elektroforeza w gradiencie denaturacji (DGGE), może być pierwszym krokiem w opracowaniu metody zapobiegania zaburzeniom procesu oczyszczania. Celem tej pracy był monitoring różnorodności bakteryjnej w osadzie czynnym bioreaktora membranowego usuwającego ścieki zanieczyszczone związkami ropopochodnymi i określenie wpływu tych związków na zmienność bakteryjną badanej biocenozy. Usunięcie związków organicznych wyrażonych wskaźnikiem zanieczyszczeń ChZT zarówno w kontrolnym, jak i eksperymentalnym bioreaktorze membranowym, wynosiło powyżej 93%. Najwyższe zastosowane stężenie związku zanieczyszczającego (frakcja P-30, próżniowy destylat ropy naftowej) wynosiło 1000 μl/l ścieków i nie miało wpływu na efektywność oczyszczania ścieków. Analiza wzorów prążkowych DGGE wykazała, że bioróżnorodność bakteryjna w bioreaktorze kontrolnym zmieniała się nieznacznie w trakcie trwania eksperymentu, podczas gdy w bioreaktorze eksperymentalnym spadła drastycznie po dodaniu dawki zanieczyszczającej o najwyższym stężeniu. Wyniki te sugerują, że stężenia modelowych związków ropopochodnych w zakresie 50 μl/l to 500 μl/l stymulują wzrost bioróżnorodności, podczas gdy zastosowanie zanieczyszczenia w stężeniu 1000 μl/l ścieków prawdopodobnie hamuje najbardziej wrażliwe procesy oczyszczania ścieków poprzez wpływ na biocenozę bakteryjną.