Degradation of 17β-estradiol and its conjugates: Effects of initial concentration and MLSS concentration

There have been many strong retrospective observations regarding adverse effects in reproductive and fertile developments in human and the wildlife caused by the endocrine disrupting compounds (EDCs) present in the aquatic environment recently. Degradation by biomass is one of the main removal mechanisms for 17β-estradiol (E2), the most important EDC, and its conjugates from sewage in wastewater treatment plants. In this batch study, the degradation rates of E2 and its conjugates were found to be affected by initial concentration of concerned pollutants and mixed liquor suspended solids (MLSS) concentration of activated sludge tested. Quantitative analysis was performed by liquid chromatography tandem mass spectrometry (LC-MS-MS). Overall, Michaelis–Menten Model adequately described the degradation of E2 and its conjugates over the range of the initial concentrations and MLSS concentrations tested. The degradation rates increased with the increase of initial concentration and MLSS concentration.     

The impact of different operating conditions on membrane fouling and EPS production

The main goal of this research was to investigate how different factors influence membrane fouling. The impact of the different concentrations of activated sludge and the amount of extracellular polymer substances (EPS) were monitored. Two pilot plants with submerged membrane modules (hollow fiber and flat sheet) were operated and the raw wastewater was used.Humic substances were identified as the major components of EPS in the activated sludge (more than 34%) in both pilot plants. As the basic constituent in permeate, humic substances were identified as the most dominant components in the effluent (61%) in both pilot plants. Conversely, proteins were mostly analyzed in permeate and supernatant below the detection limit. The total amount of EPS [mg g⁻¹ (VSS)] was similar for concentrations of activated sludge 6, 10 and 14 g L⁻¹. Carbohydrates were identified as the component of EPS which tends most to clog membranes.     

Prediction model of DnBP degradation based on BP neural network in AAO system

A laboratory-scale anaerobic-anoxic-oxic (AAO) system was established to investigate the fate of DnBP. A removal kinetic model including sorption and biodegradation was formulated, and kinetic parameters were evaluated with batch experiments under anaerobic, anoxic, oxic conditions. However, it is highly complex and is difficult to confirm the kinetic parameters using conventional mathematical modeling. To correlate the experimental data with available models or some modified empirical equations, an artificial neural network model based on multilayered partial recurrent back propagation (BP) algorithm was applied for the biodegradation of DnBP from the water quality characteristic parameters. Compared to the kinetic model, the performance of the network for modeling DnBP is found to be more impressive. The results showed that the biggest relative error of BP network prediction model was 9.95%, while the kinetic model was 14.52%, which illustrates BP model predicting effluent DnBP more accurately than kinetic model forecasting.     

The influence of fundamental design parameters on ciliates community structure in Irish activated sludge systems

The protozoan community in eleven activated sludge wastewater treatment plants (WWTPs) in the greater Dublin area has been investigated and correlated with key physio-chemical operational and effluent quality parameters. The plants represented various designs, including conventional and biological nutrient removal (BNR) systems. The aim of the study was to identify differences in ciliate community due to key design parameters including anoxic/anaerobic stages and to identify suitable bioindicator species for performance evaluation. BNR systems supported significantly different protozoan communities compared to conventional systems. Total protozoan abundance was reduced in plants with incorporated anoxic and anaerobic stages, whereas species diversity was either unaffected or increased. Plagiocampa rouxi and Holophrya discolor were tolerant to anoxic/anaerobic conditions and associated with high denitrification. Apart from process design, influent wastewater characteristics affect protozoan community structure. Aspidisca cicada was associated with low dissolved oxygen and low nitrate concentrations, while Trochilia minuta was indicative of good nitrifying conditions and good sludge settleability. Trithigmostoma cucullulus was sensitive to ammonia and phosphate and could be useful as an indicator of high effluent quality. The association rating assessment procedure of Curds and Cockburn failed to predict final effluent biological oxygen demand (BOD₅) indicating the method might not be applicable to treatment systems of different designs.     

Aerobic granular sludge: recent advances

Aerobic granulation, a novel environmental biotechnological process, was increasingly drawing interest of researchers engaging in work in the area of biological wastewater treatment. Developed about one decade ago, it was exciting research work that explored beyond the limits of aerobic wastewater treatment such as treatment of high strength organic wastewaters, bioremediation of toxic aromatic pollutants including phenol, toluene, pyridine and textile dyes, removal of nitrogen, phosphate, sulphate and nuclear waste and adsorption of heavy metals. Despite this intensive research the mechanisms responsible for aerobic granulation and the strategy to expedite the formation of granular sludge, and effects of different operational and environmental factors have not yet been clearly described. This paper provides an up-to-date review on recent research development in aerobic biogranulation technology and applications in treating toxic industrial and municipal wastewaters. Factors affecting granulation, granule characterization, granulation hypotheses, effects of different operational parameters on aerobic granulation, response of aerobic granules to different environmental conditions, their applications in bioremediations, and possible future trends were delineated. The review attempts to shed light on the fundamental understanding in aerobic granulation by newly employed confocal laser scanning microscopic techniques and microscopic observations of granules.     

Regulation of DNA synthesis by guanosine-5′-diphosphate, cyclic guanosine-3′,5′-monophosphate, and cyclic adenosine-3′,5′-monophosphate in mouse lymphoid cells

The effect of various adenine and guanine nucleotides and nucleosides on DNA synthesis was studied in various types of mouse lymphoid cells. Two out of the ten compounds tested, namely guanosine-5′-diphosphate (GDP) and cyclic guanosine-3′,5′-monophosphate (cGMP) increased the thymidine incorporation into the DNA of the spleen cells and counteracted completely or partially the inhibitory action of cyclic adenosine-3′,5′-monophosphate (cAMP) on spleen cells stimulated by various B or T cell mitogens. GDP seems to act preferentially on thymus cells while cGMP acts better on bone marrow cells. The possible significance of the results for the mechanism of the mitogenic signal is discussed.     

Removal of organic pollutants and analysis of MLSS–COD removal relationship at different HRTs in a submerged membrane bioreactor

In order to investigate the influence of hydraulic retention time (HRT) on organic pollutant removal in a submerged membrane bioreactor (SMBR), a laboratory-scale experiment was conducted using domestic sewage as influent. The dissolved oxygen (DO) concentration was controlled at 2.0– during the experimental period. The experiments demonstrated that when HRT was 3, 2 and 1 h, the reduction of chemical oxygen demand (COD) was 89.3–97.2, 88.5–97.3 and 80–91.1%, and the effluent COD was 38.9–11.2, 41.6–10.8 and 63.4–, respectively. It is suggested that an HRT of 1 h could meet the normal standard of discharged domestic sewage, and an HRT of 2 h could meet that of water reclamation. In addition, we use mathematical software MATLAB to analyse the relation of mixed liquor suspended solids (MLSS) and COD removal. The results showed that the optimum MLSS concentration should be maintained at around in the SMBR. The results also showed that the COD removal was related to HRT (τ), influent concentration (S₀) and sludge loading rate for COD removal (N_S). Moreover, the high COD removal could be achieved through adjusting τ, S₀ and N_S.