Background: This study aimed to model optimization of strategic environmental management decisions in the operation of reverse osmosis desalination, emphasizing the costs required for the environmental protection during the production of freshwater using reverse osmosis technology.
Methods: This analytical research was conducted in five cities of Hormozgan province in Iran for 18 months from February 2018 to September 2019. The research includes eight phases of defining the research problem, data collection, preliminary data analysis and decision criteria, mathematical modeling, model validation, information preparation, analysis and finally discussion, conclusions and suggestions. The main environmental issues were the carbon dioxide (CO2) release rate due to power demand and rejected brine water (RBW) were entered the mathematical model.
Results: The desalination plants of Abu Musa, Bandar Abbas, Qeshm, Sirik, and Hormoz with water production flow rate of 2100, 89 000, 5300, 3300 and 1500 m3/d can generate 2360.82, 100053.80, 5958.260, 3709.86 and 1686.30 tons/year of CO2 emissions respectively. This output requires 1.35, 57.47,3.42, 2.13 and 0.97 million USD for controlling the process, respectively. For reduction of the negative effect of RBW 0.75, 22.79, 1.78, 1.15 and 0.55 million USD respectively, is needed.
Conclusion: Recommendations for environmental impacts protection of RBW, for desalination capacity up to 50 000 m3/d, are; (a) for desalination capacity up to 50 000 m3/d; dilution the RBW using raw water before entering into the sea, (b) for capacity of 50 000-100 000 m3/d; dispersing RBW in sea using diffuser, and (c) for capacity more than 100 000 m3/d; hybrid water desalination plants and power plant. Application of power plant cooling water to dilute RBW may reduce cost.

Background: Discharging wastewaters containing antibiotic into the environment causes some adverse effects on the human health and other organisms. The present study investigated the efficiency of electropersulfate combined with hydrogen peroxide (H2O2) process as a chemical oxidation in amoxicillin (AMX) degradation.
Methods: Optimization of the significant operational independent variables was explored for removal of AMX. Central composite design (CCD) was employed as a statistical tool for experimental design. High-performance liquid chromatography (HPLC) was used for measuring AMX concentration. The most effective factors of the electro-persulfate and H2O2 on the removal efficiency of AMX such as initial concentration of AMX, initial pH, PS/H2O2 molar ratio, and the current density were measured.
Results: The optimum conditions for electro-persulfate removal efficiency of AMX to reach the degradation efficiency of higher than 95.28 ± 2.64% at reaction time of 60 minutes were obtained at pH = 4.23, AMX concentration = 31.9 mmol/L, current density = 39 mA/cm2, and PS/H2O2 molar ratio = 0.82. AMX degradation was satisfactorily predicted by the quadratic model with high possibility and confidence level of 95%. The quadratic model had high regression coefficients (R2 = 0.9964 and R2 adj = 0.9926), which was totally acceptable. The removal efficiency of AMX reduced from 87.3 ± 6.1 to 25.9 ± 9 as pH increased from 5.5 to 7.
Conclusion: According to the results, the electro-persulfate and H2O2 process can be suggested as the most effective, high efficient, and in-situ chemical oxidation for degradation of AMX.

Background: The present study aimed to assess the acute impact of erythromycin (ERY) as an inhibitor on peptone mixture utilization of activated sludge (AS) consortium.
Methods: For this purpose, the inhibition of oxygen consumption was used based on the ISO 8192:2007 procedure. In this method, the AS consortium (10-day age) was extracted from labscale membrane bioreactor, then, percentage inhibition for total, heterotrophic, and nitrifying microorganisms, in separate batch respirometric tests were calculated in the absence and presence of N-allylthiourea (ATU) as a specifc Nitrifcation inhibitor.
Results: The obtained data showed that the height of oxygen uptake rate (OUR) profles and amount of oxygen consumption reduced with increasing ERY dose. The half-maximal effective concentration (EC 50) of ERY for heterotrophic and nitrifer microorganisms were 269.4 and 1243.1 mg/L, respectively. In Run 1, the kinetic coeffcients bH, fA,H, YH, and µH were calculated as 2.61 d-1, 0.44, 0.4945 mg VSS/mg COD, and 0.047 d-1, respectively. Also, for maximum ERY concentration (1000 mg/L), the kinetic coeffcients bH., fA,H, YH, and µH were calculated as 2.27 d-1, 0.3, 0.4983 mg VSS/mg COD, and 0.0049 d-1, respectively.
Conclusion: The fndings showed that the inhibitory impact of ERY was observed as a decrease in the amount of oxygen consumption by OUR profles in rapid respirometric method (ISO 8192), which offered a novel insight for the acute inhibitory impact of this antibiotic. Also, chemical oxygen demand (COD) as an overall substrate parameter is most helpful in interpreting the behavior and the metabolic functions of AS systems.

Background: Treatment of combined industrial wastewater from industrial parks is one of the most complex and difficult wastewater treatment processes. Also, the accuracy of biological models for the prediction of the performance of these processes has not been sufficiently evaluated. Therefore, in this study, the International Association on Water Quality (IAWQ(-Activated Sludge Model No. 1 (ASM1) was implemented for the Jey industrial park in Isfahan province, Iran.
Methods: The Jey IPWWTP process is a combination of anaerobic and aerobic biological processes. To evaluate the overall performance of IPWWTP, organic compounds, suspended solids, nutrients, attached biomass, and some operating parameters were measured during 6 months. Then, the biokinetic coefficients of aerobic processes were determined using Monod equations. Finally, the aerobic processes were modeled using ASM1 implemented in STOAT software.
Results: The values of the biokinetic coefficients K, Y, Ks, Kd, and µmax were calculated as 2.7d-, 0.34 mg VSS/mg COD, 133.36 mg/L COD, 0.03d-, and 0.93d-, respectively. Based on the default coefficients and conditions of the ASM model, the difference between the experiments and model prediction was about 2 to 98%. After calibrating the ASM model, the difference between the experiments and prediction in all parameters was reduced to less than 10%.
Conclusion: Investigations showed that the default coefficients and operation conditions of the ASM1 model do not have good predictability for complex industrial wastewaters and the outputs show a low accuracy compared to the experiments. After calibrating the kinetic coefficients and operating conditions, the model performance is acceptable and the predictions show a good agreement with the experiments.

Background: Microplastics (MPs) are nowadays found in the air and in various terrestrial and aquatic environments and have become emerging pollutants. These particles can absorb other chemicals and microbial contaminants and release them into the environment and food chain. Despite the high efficiency of wastewater treatment plants (WWTPs) in removing MPs, WWTPs are still one of the major sources of MPs discharge to the environment. This study was conducted to evaluate the efficiency of MPs removal in a municipal WWTP with conventional activated sludge in Iran.
Methods: MPs particles were counted using a stereomicroscope after the initial preparation steps (sieving, chemical digestion with the catalytic wet peroxidation-oxidation and density separation with NaCl) and then analyzed for particle composition using a Raman micro-spectrometer.
Results: MPs concentration in the influent, grit chamber, primary sedimentation tank, and effluent were 843.2 ± 147.5, 315.5 ± 54.7, 80.2 ± 19.1, and 11.13 ± 3.14 items/L, respectively. The overall MPs removal efficiency of the WWTP was 98.7%, with the grit chamber, primary sedimentation tank, and secondary sedimentation tank removed 62.6%, 27.9%, and 8.2% of the total MPs, respectively. The most abundant polymers were polypropylene (PP) and polyethylene (PE).
Conclusion: Despite the effective removal of MPs in WWTP, on average 4.47 × 1011 ± 1.03 × 1011 MPs are discharged into the receiving waters through the effluent of this WWTP annually. This means that WWTPs can be one of the major sources of MPs in the environment and efforts should be made to increase the efficiency of WWTPs and equip them with advanced technologies.

Background: Based on the previous studies, antibiotics can have affected biological properties of biomass and fouling properties of mixed liquor in aeration tank. The present study was conducted to explore the fouling mechanisms of membrane bioreactor (MBR) system during the treatment of wastewater containing erythromycin (ERY) antibiotic under several mixed liquor suspended solids (MLSS) concentrations.
Methods: A lab-scale two-chamber MBR system equipped with a polypropylene hollow fiber submerged membrane was fed with synthetic wastewater containing different initial concentrations of ERY. MBR system was operated under the constant flux mode and different MLSS concentrations (5.0-13.0 g/L) and the obtained results were evaluated using different individual and combined fouling models.
Results: The variation of MLSS concentrations had not significantly affected the kind of best-fitted model. From the individual models, the standard model indicated the best performance for permeate prediction under different MLSS concentrations (R2 adj > 0.997). For all studied MLSS concentrations,
the R2 adj values of combined fouling models were higher than 0.986 and demonstrated good fitness performance of combined models compared to individual models. Overall, the cake-intermediate model showed the lowest fitness, and cake-complete and complete-standard models were the most successful models in filtrated volume prediction in comparison with other combined fouling models.
Conclusion: This study indicated that mechanistic models are suitable for fouling prediction of MBR systems in ERY removal and under a wide range of MLSS concentrations and provide valuable information on fouling mechanisms of full-scale MBR systems.