Concentration Of Mixed Liquid Suspended Solids Research Articles

Combination of biodegradation and fenton process for efficient removal of PDM/ZnO

In the present study, an investigation was conducted on the removal of polydiallyldimethylammonium chloride-acrylic-acrylamide-hydroxyethyl acrylate/ZnO nanocomposites (PDM/ZnO) through biodegradation and Fenton process coupled treatments. As revealed from the results of the chemical oxygen demand, the total organic carbon, the biochemical oxygen demand and the CO2 production analysis, PDM/ZnO could be partially biodegraded. The optimal initial pH, the mixed liquid suspended solids concentration and additional carbon source (glucose) dosage in the biodegradation were 7.0, 4.0 g/L and 1.0 g/L, respectively. On the whole, NaCl, the coexisted metal cations (Cu2+, Zn2+ and Cr3+) and additional NH4Cl inhibited the biodegradation of PDM/ZnO. PDM/ZnO was suggested to adversely affect on microbial community structure and activity. Optimum conditions for Fenton treatment were 50 mg/L Fe2+, 20 mL/L H2O2 and pH 2.0. Biodegradation showed that 64% of PDM/ZnO was removed. Besides, the combination of Fenton post-treatment could achieve an over 97% removal of PDM/ZnO. Thus, Fenton process combined biodegradation pre-treatment can act as an effective method to remove PDM/ZnO.

Investigation of textile dyeing effluent using activated sludge system to assess the removal efficiency.

In this current work, the performance of an aerobic granular sludge (AGS) for real textile wastewater was investigated based on system operational parameters evaluation. The study was performed for 90 days, and sampling was done once a week in which textile dyeing effluent from the textile mill was collected and subjected to laboratory-scale treatment. The samples from the inlet, the outlet of the wastewater plant, and within the bioreactor were collected at various concentrations of mixed liquid suspended solids (MLSS), and hydraulic retention remained the same in the investigated period of 53 h. The objective of this study was to analyze the AGS system performance assessment by evaluating the effect of different MLSS concentrations on chemical oxygen demand (COD), total suspended solids (TSS), and oil/grease removal from real-based textile water. The results showed that removal of organic material from the process water increases with an increase in MLSS concentration in the bioreactor and gradually shifts removal of COD from 91.2% to 94.5%. As the concentration of microorganisms in the reactor (aeration tank) increases, the degradation of waste organics in the wastewater increases as well. Moreover, the % removal of TSS (83.5% to 98%) and removal of oil/grease (62.5% to 76.4%) were also increased. These results ultimately suggest that the utilization of an activated sludge system can effectively treat complex and highly polluted denim textile wastewater to avoid secondary pollution posed by this industry. PRACTITIONER POINTS: The effectiveness of aerobic granular sludge was investigated for industrial textile effluent. The increase in MLSS results in increase of % COD removal efficiency to 94.5%. The AGS system can efficiently treat complicated and highly contaminated textile wastewater.

An evaluation of lysozyme enzyme and thermal pretreatments on dairy sludge digestion and gas production.

Anaerobic digestion is one of the common methods of managing and stabilizing sludge. However, due to the limitations of the biological sludge hydrolysis stage, anaerobic decomposition is slow and requires a long time. This study evaluated the effects of thermal (80 °C) (TH-PRE) and a combination of thermal with the lysozyme enzyme (LTH-PRE) pretreatments on the enhancement of anaerobic activated sludge digestion. Response surface methodology was implemented to optimize enzyme pretreatment conditions (enzyme and mixed liquid suspended solids concentration). The results showed that both pretreatment methods increase soluble chemical oxygen demand (COD) and reduces total and volatile suspended solids (VSS), and phosphate concentration. The COD removal rate in LTH-PRE and TH-PRE was 95% and 81%, respectively. The value of VSS reduction in LTH-PRE and TH-PRE was 41% and 31%, more than the control operation, respectively. The biogas production in LTH-PRE and in TH-PRE also increased by 124% and 96%, respectively.

Influence of mixed liquid suspended solids and hydraulic retention time on oxygen transfer efficiency and viscosity in a submerged membrane bioreactor using pure oxygen to supply aerobic conditions

The performance of a wastewater bench-scale membrane bioreactor (MBR) treatment plant using pure oxygen conditions was monitored daily to provide aerobic conditions. The results showed the capacity of the MBR system to remove organic material over at hydraulic retention time (HRT) of 12 h and 18 h. The alpha-factors of aeration were determined at three different mixed liquid suspended solids (MLSS) concentrations, in order to understand the system performance when pure oxygen was used to provide the aerobic conditions of the MBR system. Under these working conditions, an alpha-factor in the range 0.90–0.12 was obtained when the HRT of 18 h was performed, and the MLSS concentration increased from 4300 to 10,275 mg/L. Additionally, an alpha-factor in the range of 0.28–0.02 was obtained at HRT of 12 h and the MLSS increased from 4071 to 11,192 mg/L. Our study suggested significant changes in the behaviour of the biological system (viscosity, aeration efficiency, organic matter removal) when the concentration of MLSS was increased and the HRT decreased in the bioreactor, decreasing the aeration efficiency in both cases. Furthermore, the efficiency of aeration seems to be more affected by MLSS concentration than by HRT under our operating conditions over the range studied.

Kinetic study and oxygen transfer efficiency evaluation using respirometric methods in a submerged membrane bioreactor using pure oxygen to supply the aerobic conditions

The performance of a wastewater bench-scale ultrafiltration membrane bioreactor (MBR) treatment plant using pure oxygen to supply the aerobic conditions for 95 days was studied. The results showed the capacity of the MBR systems to remove organic material under a hydraulic retention time of 12 h and a sludge retention time of 39.91 days. Aeration represents its major power input; this is why the alpha-factor of the aeration and kinetic parameters (design parameters) were determined when the mixed liquid suspended solids (MLSS) was increased from 3420 to 12,600 mg/l in order to understand the system. An alpha-factor in the range 0.462–0.022 and the kinetic parameters measured with the respirometric method ( K M of 73.954–3.647 mg/l, k d of 0.0142–0.104 day −1, k H of 0.1266–0.655 day −1, and the yield mean coefficient of 0.941) were obtained. Our study suggested significant changes in the behaviour of the biological system when the concentration of MLSS was increased.

Development of a correlation to study parameters affecting nitrification in a domestic wastewater treatment plant

AbstractBACKGROUND: Nitrification performance of an activated sludge reactor treating weak domestic wastewater was investigated for 11 months. Ammonia nitrogen removals were investigated as a function of wastewater composition and operational conditions. Backward elimination experimental design was used to determine the influence of the most important independent variables on NH3‐N removal efficiencies. Influent ammonia and biological oxygen demand (BOD5) concentrations, hydraulic retention time (HRT), mixed liquid suspended solids (MLSS), temperature, pH and dissolved oxygen (DO) concentration were considered as independent variables. This study aimed to find the most important parameters to describe nitrification performance.RESULTS: The presence of nitrification was confirmed by ammonia and nitrate variations throughout the reactor; ammonia oxidizing bacteria (AOB) populations were determined using a fluorescence in situ hybridization (FISH) method. MLSS concentration, influent BOD5 concentration and temperature were found to be the most influential factors on nitrification performance. The empirical correlation using multiple linear regressions was statistically significant and produced an adjusted coefficient of multiple determinations (R2adj) of 92.5%.CONCLUSION: Correlation provides a good understanding of the various parameters that affect the nitrification process, and could be extended to other case studies. Using these results, operators can apply proper operational strategies to maintain nitrification in wastewater treatment plants. Copyright © 2007 Society of Chemical Industry

Application of fractal permeation model to investigate membrane fouling in membrane bioreactor

Cake layer formed on membrane surface presents a major challenge to membrane permeation, and it can be considered as a porous media. Determination of the cake layer permeability is critical for an accurate analysis and design of membrane filtration. A permeation model, based on fractal theory and Darcy's law, for evaluating cake layer permeability in microfiltration of activated sludge wastewater was developed. The cake layer permeability was derived and found to be a function of the pore-area fractal dimension and microstructural parameters. The validity of the model was studied systematically in this paper. The permeation model was applied to study the effect of mixed liquid suspended solids (MLSS) concentration, particle size distribution (PSD) and extracelluler polymeric substance (EPS) on cake layer permeability in a submerged membrane bioreactor. Results showed that the permeation model was a useful tool to study the micromechanism of membrane fouling. There was a close correlation between MLSS concentration and cake layer permeability. There were a slight and a distinct decrease of the cake layer permeation as MLSS increased less and larger than 10,000 mg/L, respectively. PSD and EPS are two significant factors affecting cake layer permeability in membrane bioreactor. Effect of activated sludge on cake layer permeability was mainly caused by EPS and small particles attached on membrane surface.