Comparison of EDCs removal in full and pilot scale membrane bioreactor plants: Effect of flux rate on EDCs removal in short SRT.

Currently, it is estimated that over 1 billion people are short of adequate portable water and this is expected to increase to 2.5 billion in the year 2025. Membrane Bioreactors (MBR) are now accepted as important tools to extend the availability of water by facilitating the reuse of wastewaters. Sludge Retention Time (SRT) and liquid flux rate are the two most important parameters for controlling the MBR process. In this study, the removal of selected endocrine disrupter compounds (EDCs), diltiazem, progesterone, estrone (E1), carbamazepine (Cbz) and acetaminophen (Acet), by one full scale (VRM) and one pilot scale (clear-box) MBR plants was investigated. During the study, sludge age was set at 10 days and the sludge concentration was fixed at about 5.0 g/L. The transmembrane pressure (TMP) got higher with either increasing flux or sludge concentration in the membrane chamber. Therefore, changing the flux from 13 to 30 L/m2-h in both plants caused enhancement in TMP from -25 to -300 mbar in the clear-box and from -160 to over -350 in the full scale MBRs. It was understood that flux had very little effect on the removal of EDCs at very low concentrations. Moreover, diltiazem was completely removed in the full scale whereas no removal was achieved in the pilot scale. Estrone and progesterone were completely removed by biodegradation in both plants. Acetaminophen was completely removed in the full scale plant whereas over 95% removal was achieved in the pilot scale MBR.

Removal of endocrine disrupting compounds in a lab-scale anaerobic/aerobic sequencing batch reactor unit.

The fate and removal of six selected endocrine disrupting compounds in a lab-scale anaerobic/aerobic (A/O) sequencing batch reactor (SBR), operating at 5 days, solids retention time (SRT) were investigated. A carbamazepine (CBZ), acetaminophen (ATP), diltiazem (DTZ), butyl benzyl phthalate (BBP), estrone and progesterone mix was spiked as model endocrine disrupting compounds (EDC) into domestic wastewater obtained from a nearby sewage treatment plant. The influent, effluent and sludge samples from the SBR unit were analysed by using an LC/MS/MS instrument equipped with electrospray ionization. More than 80% removal was observed for all the EDCs tested. It was found that biodegradation is the most important mechanism for BBP, ATP and progesterone. Biodegradation constants were calculated according to the simplified Monod model for these compounds. The DTZ seemed to have lower rate of biodegradation. The CBZ appeared totally resistant to biodegradation. However, it presented a high rate of sorption onto the sludge and was thereby treated. This contradicts with the literature studies.

Application of ADM1 model to a full-scale anaerobic digester under dynamic organic loading conditions.

The IWA Anaerobic Digestion Model No. 1 (ADM1) was used to simulate the full-scale anaerobic sludge digester of Ankara Central Wastewater Treatment Plant. The digester is a completely mixed, once through continuous flow type which is being fed with a primary and secondary sludge mixture. The variability and unpredicted nature of the primary sludge composition was expected to challenge the model. A one-year dynamic data set from the digester was used for model calibration and validation in the study. The standard ADM1 model was corrected in the study with regard to nitrogen and carbon mass balances. A good correlation between the measured and simulated data was obtained for biogas yield, total volatile fatty acids and pH after heuristically calibrating stoichiometric and kinetic parameters of the ADM1 model. The simulation is sensitive to influent composition.

Influence of nickel (II) and chromium (VI) on the laboratory scale rotating biological contactor.

High concentration of heavy metals is toxic for most microorganisms and cause strict damage in wastewater treatment operations and often a physico-chemical pretreatment prior to biological treatment is considered necessary. However, in this study it has been shown that biological systems can adapt to Ni (II) and Cr (VI) when their concentration is below 10 and 20 mg/L, respectively. The aim of this study was to evaluate the effect of Ni (II) and Cr (VI) on the lab-scale rotating biological contactor process. It was found that, addition of Ni (II) up to 10 mg/L did not reduce the chemical oxygen demand removal efficiency and on the contrary concentrations below 10 mg/L improved the performance. The influent Ni (II) concentration of 1 mg/L was the concentration where the treatment efficiency produced a maximum COD removal of 86.5%. Moreover, Ni (II) concentration above 10 mg/L was relatively toxic to the system and produced lower treatment efficiencies than the baseline study without Ni (II). Turbidity and suspended solids removals were not stimulated to a great extent with nickel. Addition of Ni (II) did not seem to affect the pH of the system during treatment. The dissolved oxygen concentration did not drop below 4 mg/L at all concentrations of Ni (II) indicating aerobic conditions prevailed in the system. Experiments conducted with Cr (VI) revealed that addition of Cr (VI) up to 20 mg/L did not reduce the COD removal efficiency and on the contrary concentrations below 20 mg/L improved the performance. The influent Cr (VI) concentration of 1 mg/L was the concentration where the treatment efficiency produced a maximum COD removal of 88%. Turbidity and SS removals were more efficient at 5 mg/L Cr (VI) concentration, rather than 1 mg/L, which lead to the conclusion that 5 mg/L Cr (VI) concentration is the optimum concentration, in terms of COD, turbidity and SS removals. Similar with Ni (II) experiments, addition of Cr (VI) did not significantly affect the pH value of the effluent. The DO concentration remained above 5 mg/L.

Modeling of a large-scale wastewater treatment plant for efficient operation.

Environmental legislations in the Western world impose stringent effluent quality standards for ultimate protection of the environment. This is also observed in Turkey. The current paper presents efforts made to simulate an existing 0.77 million m3/day conventional activated sludge plant located at Ankara, AWTP. The ASM1 model was used for simulation in this study. The model contains numerous stoichiometric and kinetic parameters, some of which need to be determined on case by case bases. The easily degradable COD (S(S)) was determined by two methods, physical-chemical and respirometric methods, namely. The latter method was deemed unreliable and rejected in the further study. Dynamic simulation with SSSP program predicted effluent COD and MLSS values successfully while overestimating OUR. A complete fit could only be obtained by introducing a dimensionless correction factor (etaO2 = 0.58) to the oxygen term in ASM1.