Investigating biodegradation of polyethylene and polypropylene microplastics in Tehran DWTPs.

Microplastic (MP) pollution is a growing concern and various methods are being sought to alleviate the level of pollution worldwide. This study investigates the biodegradation capacity of MPs by indigenous microorganisms of raw water from Tehran drinking water treatment plants. By exposing polypropylene (PP) and polyethylene (PE) MPs to selected microbial colonies, structural, morphological, and chemical changes were detected by scanning electron microscope (SEM), cell weight measurement, Fourier transform infrared (FTIR), Raman spectroscopy test, and thermal gravimetric analysis (TGA). Selected bacterial strains include Pseudomonas protegens strain (A), Bacillus cereus strain (B), and Pseudomonas protegens strain (C). SEM analysis showed roughness and cracks on PP MPs exposed to strains A and C. However, PE MPs exposed to strain B faced limited degradation. In samples related to strain A, the Raman spectrum was completely changed, and a new chemical structure was created. Both TGA and FTIR analysis confirmed changes detected by Raman analysis of PP and PE MPs in chemical changes in this study. The results of cell dry weight loss for microbial strains A, B, and C were 13.5, 38.6, and 25.6%, respectively. Moreover, MPs weight loss was recorded at 32.6% for PP MPs with strain A, 13.3% for PE MPs with strain B, and 25.6% for PP MPs with strain C.

Optimisation of soil washing method for removal of petroleum hydrocarbons from contaminated soil around oil storage tanks using response surface methodology.

Total petroleum hydrocarbons (TPHs), which are often found in soil, water, sediments, and air. These compounds are a type of pollutant that can have a serious negative impact on living things and human health. Soil washing method is a remediation technique used to remove contaminants from the soil. This process involves the use of water or other solvents to extract contaminants from the soil, followed by separation and disposal of the contaminated solution. This research engineered the effectiveness of soil washing method to remove TPHs from a genuine, sullied soil sample. After analyzing the physical and chemical properties of the soil, the Box-Benken Design (BBD) technique was used to optimize the variables that influence the process's effectiveness. A quadratic model was suggested based on the BBD design, correlation coefficients, and other factors. The minimum, maximum and mean removal of TPHs during the stages of the study were 63.5, 94.5 and 76.7%, respectively. The correlation between the variables was strong, as shown by the analysis of variance (ANOVA), F-value (1064.5) and P-value (0.0001), and the proposed model was highly significant. The most effective soil washing method (SWM) was obtained with pH 7.8, liquid to solid ratio 50:1, reaction time 52 min, surfactant concentration 7.9 mg kg-1, and three washings. A removal rate of 98.8% was accomplished for TPHs from the soil in this context. The kinetic results indicate that the kinetic of TPHs removal follows the first-order kinetics (R2 = 0.96). There was not a major difference in the process's efficiency based on temperature. The removal efficiency heightened from 0 to 150 rpm and then remained steady. Introducing air flow increased the rate of removal, and the combination of ultrasonic waves with the reaction environment increased the process efficiency and decreased the time for the process and the amount of times it needed to be washed. An analysis of the washed soil both physically and chemically revealed a substantial decrease in the concentration of other elements.

Effect of Fe and Al based coagulants and disinfectants on polyethylene microplastics removal in coagulation process through response surface methodology.

Microplastic (MP) pollution has been rising as a threatening risk and recently has appealed to the attention of more researchers. In this study, influential parameters affecting the removal rate of polyethylene microplastics (PEMPs) were optimized through response surface methodology (RSM). In Box Behnken Design (BBD), independent parameters were pH, PEMP size, coagulant dosage and polyacrylamide dosage. Two experimental sets were conducted, one with ferric chloride and the second with poly aluminum chloride as two commonly applied coagulants in drinking water treatment plants (DWTPs). Comparing the results of optimized parameters, PAC was a better coagulant with the predicted removal rate of 58.19%, while the removal rate with ferric chloride as a coagulant was predicted to be 56.37%. Moreover, some experiments were conducted to analyze the effect of ozone gas and sodium hypochlorite as disinfectants on removal rate. The highest removal rate was observed when 2 ppm of O3 was added to the solution coagulated with optimal dosage of PAC, reaching the removal rate of 76.8%.

Optimization of the biological salt removal process from artificial industrial wastewater with high TDS by Spirulina microalga using the response surface method.

This study aimed to examine the direct applicability of Spirulina maxima as a new conceptual method for removing total dissolved solids (TDS) from artificial industrial wastewater (AIW). In this study, live microalgal cells were used in a photobioreactor for TDS removal. The effects of TDS levels, pH, light intensity, and light retention time on microalgal growth and TDS removal were investigated, and optimal conditions were determined using the response surface method and Box-Behnken Design (RSM-BBD). The calculated values of coefficient of determination (R2), adjusted R2, and predicted R2 were 0.9754, 0.9508, and 0.636, respectively, which are close to the R2 values and validated the proposed statistical model. A second-order model could optimally determine the interactions between the studied variables according to the one-way analysis of variance (ANOVA). The results showed that increasing TDS levels reduced microalgal growth and TDS removal efficiency in AIW. S. maxima reduced TDS by 76% and 47% at TDS concentrations of 2,000-4,000 mg/L, respectively, when used in AIW. Maximum biomass efficiency (1.8 g/L) was obtained at a TDS concentration of 2,000 mg/L with other parameters optimized.

Simultaneous study of the interaction effect of chemical and hydrothermal pretreatment on the yield of methane produced from municipal waste.

Municipal waste has the potential to be a significant source of energy production. This study investigated pretreatment methods such as NaOH, hydrothermal, and ozonation to increase biomethane production from municipal waste. In addition, these pretreatments were further evaluated using ultrasonic pretreatment after achieving optimal conditions by RSM CCD methods. The optimum pretreatment conditions were observed to be 8% NaOH concentration, 132 °C hydrothermal temperature, and O3 equal to 0.19 g/g TS. The maximum biomethane produced and achieved during the tests was 394 mL/kg TS, which increased to 410 mL/kg TS after ultrasonic pretreatment. The best sCOD reduction in the optimal pretreatment conditions and after the ultrasonic pretreatment was 87% and 91%, respectively. Also, in the absence of ozone pretreatment, the highest yields of biomethane and biogas occurred at a 6.4% concentration of NaOH and a temperature of 135 °C; however, in the presence of ozone, the yield of biomethane and biogas produced was greater and the inhibitory effect of sodium hydroxide also occurs in higher amounts. Experiments have shown that ozonation increases biomethane production rather than increasing biogas production (hence the ratio of methane to biogas).

Optimization of polypropylene microplastics removal using conventional coagulants in drinking water treatment plants via response surface methodology.

Background and purpose: The ubiquitous presence of microplastics (MPs) in aquatic environments has been studied widely. Due to toxicological impacts of MPs and associated contaminants, it is crucial to understand the performance of MPs removal in drinking water treatment plants (DWTPs). Few studies have investigated removal characteristics of MPs via coagulation/flocculation processes, yet removal characterization of polypropylene microplastics (PPMPs) in this process is poorly understood. This study aims to optimize coagulation of virgin PPMPs in conventional DWTPs. Methods: In this study, samples were synthesized through response surface methodology (RSM), polyaluminium chloride (PACl) was applied as a conventional coagulant to remove PPMPs in the coagulation/flocculation process, which has the least density among common polymers and is one of the most abundant manufactured polymers worldwide. A particle size analyzer (PSA) was used to measure floc size at different pH levels. Additionally, a zeta potential analyzer was used to measure stability of the flocs at different pH. Results: Base on the experimental range in Design-Expert, results revealed that the optimum removal rate was predicted to be at pH 9, PACl concentration of 200 ppm, polyacrylamide (PAM) concentration of 21 ppm, and PPMPs size of d < 0.25 mm. According to the predicted optimum condition, actual and predicted removal rates were 18.00 ± 1.43% and 19.69%, respectively. Conclusion: According to this study, PACl is not capable of efficiently removing virgin PPMPs in DWTPs, thereby exposing humans to eco-toxicological impacts of PPMPs through tap water.

Identification of microplastics in conventional drinking water treatment plants in Tehran, Iran.

The presence of microplastics (MPs), as an emerging pollutant is a growing concern in drinking water, yet most of the studies have been carried out in surface waters and wastewater treatment plants and there are few studies on MPs in drinking water treatment plants (DWTPs). This study investigates these particles in three different conventional DWTPs in the city of Tehran, Iran, and aims to analyze these particles down to the size of 1 µm. A scanning electron microscope was utilized in this study to quantitatively analyze MPs. Accordingly, the average abundance of MPs in raw and treated water samples varied from 1996 ± 268 to 2808 ± 80 MPs L-1 and 971 ± 103 to 1401 ± 86 MPs L-1, respectively. While particles smaller than 10 µm comprised 65-87% of MPs. Moreover, µ-Raman spectroscopy was used to characterize MPs. As the results, polypropylene, polyethylene terephthalate, and polyethylene were the most abundant identified polymers among MPs, comprising more than 53% of particles. Additionally, MPs were categorized as fibers, fragments, and spheres. This study fills the knowledge gap of MPs presence in Tehran conventional DWTPs which is of high importance since they supply drinking water for more than 8 million people and investigates the performance of conventional DWTPs in removing MPs. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40201-021-00737-3.

Effect of Base Transceiver Station (BTS) waves on some blood factors in domestic pigeons: an experimental study.

PURPOSE: BTS waves are one of the most important environmental pollutants, but there is inadequate data of its effects on living creatures. Birds have major role in environmental balance and hematologic factors are good describers of animal health. Therefore, we studied hematological factors in pigeons to assess the health effects of BTS waves in urban birds. METHODS: This experiment has been run on 120 six month-old pigeons. After adaptation to laboratory settings, they divided to six random groups of distance from BTS and daily exposure time. G1: 50 cm/30 min, G2: 100 cm/30 min daily, G3: 150 cm/30 min, G4: 50 cm/60 min, G5: 100 cm/60 min and G6: 150 cm/60 min. Daily exposure done for 30 consecutive days. Hematologic studies done before and after exposure for analysis of WBC, Neut, Mono, Lymph, RBC, Hb, HCT, MCV, MCHC and platelets. Results processed statistically by SPSS software. RESULTS: The results of this study showed a significant difference between the six experimental groups. The results showed distance from the BTS source had the largest effect on PLT followed by HCT, MCV, MCHC, Neut, Hb, RBC, Lymph, WBC, and Mono, respectively. Moreover, the duration of exposure to BTS wave had the largest effect on Mono followed by PLT, Neut, MCV, MCHC, WBC, HCT, Lymph, RBC and Hb, respectively. CONCLUSIONS: Study showed that increasing exposure time and decreasing distance from the wave source have significant effect on hematologic factors. The distance has more effect than exposure time. Further investigation on protection and reducing the side effects are recommended.

Optimization of zinc bioleaching from paint sludge using Acidithiobacillus thiooxidans based on response surface methodology.

The reduction of zinc metal in the paint sludge, a hazardous waste, was investigated using Acidithiobacillus thiooxidans by a two-stage bioleaching process. This process was performed using the response surface methodology (RSM) method based on the central composite design (CCD). Four variables, a temperature range of 32-34.5-37 °C, rotation speed of shaker 120-150-180 rpm, pH of 4.2-3.2-2.2, and particle sizes of 1-2-3 mm, were used to optimize the experiments. The results showed that with a constant pulp density of 10 g/L at 32 °C, shaker speed of 120 rpm, a particle size of 1 mm and pH of 4.2, the highest removal predicted by the software (Design Expert version 11) was 22.89%. Repeating the experiments confirmed a decrease in zinc to the nearest predicted point. According to the ANOVA result, the rotation speed of the shaker has the greatest effect on the bioleaching process, followed by the two variables of the rotation speed of shaker and pH together affects. After the bioleaching process, energy dispersive X-ray (EDX) and mapping analysis showed quantitative changes in the chemical composition of the paint sludge, and morphological changes of texture were confirmed by scanning electron microscopy (SEM).

Comparing the performance of the conventional and fixed-bed membrane bioreactors for treating municipal wastewater.

Membrane bioreactor (MBR) is relatively a new technology in wastewater treatment. It can efficiently remove soluble and suspended organics. However, it may constantly encounter bio-fouling and cannot efficiently remove nutrient pollutants. These two deficiencies have motivated researchers to upgrade the design and operation of conventional MBR (CMBR). This study evaluates the performance of hybrid fixed bed MBR (FBMBR) treating real domestic wastewater in different operational conditions. It also compares the experimental results of FBMBR with the CMBR. For this purpose, two identical reactors are constructed as CMBR and FBMBR. Each module contains the net volume of 140 L and is operated continuously in two aerobic (DO > 4 mg/L) and anoxic (DO < 1 mg/L) conditions with average organic loading rates (OLRs) of 0.58, 0.71 and 1.55 kgCOD/m3d. The pore sizes of flat sheet membranes are 0.2-0.8 µm with total surface area of 1.4m2 per module. The experimental results revealed that the removal efficiencies of BOD, COD and TSS are above 95 % in both CMBR and FBMBR in all operating conditions. However, fouling occurs with lower rates in FBMBR. The growing rate of transmembrane pressure (TMP) in aerobic condition is 1.7mBar/day in CMBR, while it reduces to 1.2mBar/day for FBMBR in solid retention time (SRT) of 75 days and OLR of 0.58 and 0.71 kgCOD/m3d. In anoxic condition with SRT of 100 days and OLR of 1.55 kgCOD/m3d, the TMP in FBMBR is 59 % of CMBR. In addition, total nitrogen (TN) removal is between 12 % (aerobic) and 27 % (anoxic) in CMBR, while it is between 25 % (aerobic) and 49 % (anoxic) in FBMBR. Total phosphorous (TP) removal also ranges between 50 and 66 % in CMBR, while it is between 51 and 86 % in FBMBR. Consequently, using hybrid systems of FBMBR can reduce membrane fouling rate and improve nutrient removal efficiency in comparison with CMBR. This approach can reinforce the biological treatment efficiency and preserve permeate quality in higher OLRs or in lower DO level.