Treatment of tomato paste wastewater by electrochemical and membrane processes: process optimization and cost calculation.

This study investigated the treatment of wastewater from tomato paste (TP) production using electrocoagulation (EC) and electrooxidation (EO). The effectiveness of water recovery from the pretreated water was then investigated using the membrane process. For this purpose, the effects of independent control variables, including electrode type (aluminum, iron, graphite, and stainless steel), current density (25-75 A/m2), and electrolysis time (15-120 min) on chemical oxygen demand (COD) and color removal were investigated. The results showed that 81.0% of COD and 100% of the color removal were achieved by EC at a current density of 75 A/m2, a pH of 6.84 and a reaction time of 120 min aluminum electrodes. In comparison, EO with graphite electrodes achieved 55.6% of COD and 100% of the color removal under similar conditions. The operating cost was calculated to be in the range of $0.56-30.62/m3. Overall, the results indicate that EO with graphite electrodes is a promising pretreatment process for the removal of various organics. In the membrane process, NP030, NP010, and NF90 membranes were used at a volume of 250 mL and 5 bar. A significant COD removal rate of 94% was achieved with the membrane. The combination of EC and the membrane process demonstrated the feasibility of water recovery from TP wastewater.

The new era hypothesis of coastal degradation: G(s) elements-gallium, gadolinium, and germanium.

Mining of precious metals contributes to environmental pollution, especially in coastal areas, and conventional treatment methods are not always effective in removing metal contaminants. Some of these metals, such as gadolinium, germanium and gallium, have caused increasing concern worldwide, as little is known about their current concentrations in the aquatic environment and their biological significance. Therefore, the aim of this study was to determine for the first time the variation of average G(s) concentrations (gallium, gadolinium and germanium) by month/season/site differences along the coast of Istanbul. The ecological risk index was calculated to assess the contamination of seawater and to serve as a diagnostic tool for the mitigation of water pollution. The average distribution G(s) in seawater was in the following order: Ga > Gd > Ge. In addition, the potential ecological risk in the sampling areas ranged from 68 to 1049. Of the three metals, Gd poses the highest ecological risk (grade III). In the spatial distribution of ecological risks, Gd mainly originated from discharges from wastewater treatment plants. Therefore, the sources of the anthropogenic Gd anomaly in wastewater should be identified, as this indicates the possibility of human exposure to potentially harmful anthropogenic compounds.

Potential Ecological Risk Assessment of Critical Raw Materials: Gallium, Gadolinium, and Germanium.

In recent years, the demand for critical raw materials such as gallium, gadolinium and germanium (G(s)) has steadily increased in various industries. However, treatment or recycling rates of these elements are extremely low, which can lead to environmental pollution. An assessment of the ecological risks was also not possible until now, as there were no calculated toxicity coefficients for G(s). In this study, a well-known method, the so-called potential ecological risk index (PERI), was used for the first time to calculate the toxicity coefficients of these elements using data from recent literature studies on G(s) elements. The toxicity coefficient of each of the three elements was determined as five (5). The results show that G(s) have the same toxicity coefficient as Cu and Pb and are higher than that of Cr. The ecological risk index results varied from 4 to 414, 0.98 to 25.98 and 2.50 to 284.64 for Ga, Gd and Ge, respectively. The results show that Ga and Ge pose high ecological risk while the Eri of Gd is low. The toxicity coefficients of these elements have been calculated for the first time in the literature and provide a practical use for calculating the potential ecological risk index.

Investigation of two different size microplastic degradation ability of thermophilic bacteria using polyethylene polymers.

There are several studies stating that many types of microplastics cannot be retained completely by conventional wastewater treatment systems. Therefore, it is necessary to prevent the discharge of these microplastics to the ecological system. The objective of this study was to investigate the biodegradation ability of two different size of PE (50 and 150 µm) by using two Gram-positive, spore-forming, rod-shaped, and motile thermophilic bacteria, called strain Gecek4 and strain ST5, which can hydrolyse starch, were isolated from the soil's samples of Gecek and Ömer hot-springs in Afyonkarahisar, Turkey, respectively. Phenotypic features and 16S rRNA analyzing of strains also studied. According to these results, Gecek4s and ST5 were identified as Anoxybacillus flavithermus Gecek4s and Bacillus firmus ST5, respectively. Results showed that A. flavithermus Gecek4s could colonise the polymer surface and cause surface damage whereas B. firmus ST5 could not degrade bigger-sized particles efficiently. In addition, morphological changes on microplastic surface were investigated by scanning electron microscopy (SEM) where dimensional changes, irregularities, crack, and/or holes were detected. This finding suggests that there is a high potential to develop an effective integrated method for plastic bags degradation by extracellular enzymes from bacteria.

Impact of coastal wastewater treatment plants on microplastic pollution in surface seawater and ecological risk assessment.

This study aims to understand the influence of wastewater treatment plant discharge on the microplastic status in the surface seawater of Istanbul. For this purpose, for the first time, the distribution, composition, and ecological risk of microplastics at nine sampling stations on the southern coast of Istanbul, Marmara, were investigated at monthly intervals over a one-year period. The results showed that the microplastic abundance ranged from 0 to over 1000 particles per liter. Fibers were the dominant form at all stations. Microplastics 249-100 µm were the dominant size, and transparency was the color most found at all stations. Polyethylene and ethylene-vinyl acetate were the major types of microplastics, accounting for 50% overall. The pollution load index revealed that over 70% of sampling stations were at hazard level I. However, the hazardous index was categorized as level III with a value of 662.3 due to the presence of the most hazardous polymer named polyurethane. Further investigations into the risk assessment of MP can reveal crucial knowledge for understanding the microplastic cycle.

Isolation of Thermophilic Bacteria and Investigation of Their Microplastic Degradation Ability Using Polyethylene Polymers.

Microplastics (MPs) pose potential public health challenges because of their widespread occurrences in all environmental compartments. While most studies have focused on the occurrence fate of microplastics in wastewater treatment systems, the biodegradation of microplastics in wastewater is generally little understood. Therefore, we used two Gram-positive and thermophilic bacteria, called strain ST3 and ST6, which were identified by morphological, biochemical, physiological, and molecular analyses, to assess the growth and biodegradation potential of two different sized (50 and 150 m) polyethylene particles. The degradation was monitored based on structural and surface morphological changes. According to 16S rRNA analyses, ST3 and ST6 were identified as Anoxybacillus flavithermus ST3 and Anoxybacillus sp. ST6, respectively. The occurrence of cracks, holes, and dimensional changes was detected by scanning electron microscopy. Moreover, critical characteristic absorption band formation and modifications were determined by Fourier transform infrared spectroscopy. In addition to these, it was found that Anoxybacillus flavithermus ST3 and Anoxybacillus sp. ST6 produced high level of alpha-Amylase. These results showed that thermophilic bacteria are capable of the biodegradation of microplastics and production of alpha-Amylase.

Synthesis of graphite/rGO-modified fungal hyphae for chromium (VI) bioremediation process.

Bioremediation is a promising technology that can eliminate the drawbacks of conventional treatment methods in removing harmful toxic metals including chromium(VI). Therefore, in this study, fungal hyphae modified with graphite and reduced graphene oxide were synthesized and assessed for their potential to bioremediate heavy metals for the first time in the literature. The effects of the carbon-based materials on microbial structure were characterized using scanning electron microscopy analysis. Thermogravimetric, RAMAN, X-ray diffraction, and enzymatic analyzes were performed to determine the role of functional groups. In addition, batch adsorption experiments utilizing response surface methodology were conducted to optimize operating parameters such as time (1-11 h), chromium (10-50 mg/L), and graphite/reduced graphene oxide (0.1-1 g/L). The maximum adsorption capacity with the graphene fungal hyphae was determined to be 568 mg.g-1, which is 9.7 times that of the crude fungal hyphae. The Cr(VI) removal for fungal hyphae-graphite and fungal hyphae-reduced graphene oxide biocomposites was 98.25% and 98.49%, respectively. The isothermal and kinetic results perfectly matched the 2nd order pseudo-model and Langmuir model in terms of the nature of the adsorption process. The laboratory scale test results indicate that fungal hyphae modified with graphite and reduced graphene oxide have a high adsorption capacity, suitable for the removal of chromium (VI) from wastewater.

Treatment of vegetable oil wastewater by a conventional activated sludge process coupled with electrocoagulation process.

The present work aims to study chemical oxygen demand (COD), oil-grease, and color removal from vegetable oil wastewater by combined electrocoagulation and activated sludge processes. For this purpose, the sample was pretreated using electrocoagulation by various optimization parameters such as electrode type (Al-Al and Fe-Fe), current density (100-400 A/m2 ), pH (2-8), and electrolysis time (15-180 min). The results showed that 89.3% of COD, 100% of oil-grease, and 66.2% of color were removed by electrocoagulation under the conditions of 300-A/m2 current density, pH 2, and 180-min reaction time with Al-Al electrode pairs. Then, the effluent of electrocoagulation was treated by an activated sludge process. The results depicted that the activated sludge process was also effective for vegetable oil wastewater treatment and it enhanced 98.9% COD and 79.2% color removal efficiency. The effluent of the combined process was very clear, and its quality exceeded the direct discharge standard of the water pollution control regulation. The laboratory-scale test results indicate that the combined electrocoagulation and activated sludge process is feasible for the treatment of vegetable oil wastewater. PRACTITIONER POINTS: Vegetable oil wastewater was treated by combination of electrocoagulation and activated sludge processes. The combined electrocoagulation and activated sludge processes supplied 99.9% COD, 100% oil-grease, and 93.0% color removal efficiency. The laboratory-scale test results indicate that the combined EC-SBR processes were feasible for the treatment of vegetable oil wastewater.

The spatial and temporal changes of beach litter on Istanbul (Turkey) beaches as measured by the clean-coast index.

Possible access routes of macro and mesoplastics, acting as the main sources of pollution in the coastal ecosystem, are examined as a case study on four beaches along the Istanbul coast. A total number of 3787 items belonging to 12 categories of debris types were collected as follows: macroplastics 47.8%; mesoplastics 9.2%; and others 43.0% such as paper pieces, glass pieces and metal beverage cans. Clean-coast and carbonyl indexes were also used to identify the level of cleanliness of the sampling sites. The clean-coast index revealed that all of the sample sites were categorized as extremely dirty. Moreover, carbonyl index results indicate that 35.7% of the samples were at a high oxidation level indicating that some of the particles relatively spend more time on beaches. The litter concentration and surface oxidation results were addressing issues that should be taken into consideration to improve litter management strategies of the beaches.

Removal of microplastics from wastewater through electrocoagulation-electroflotation and membrane filtration processes.

Wastewater treatment plants (WWTPs) are one of the major vectors of microplastics (MPs) pollution for the recipient water bodies. Therefore, the recovery of MPs from WWTPs is extremely important for decreasing their accumulation and impact in aquatic systems. In this present study, the electrocoagulation-electroflotation (EC/EF) and membrane filtration processes were investigated in removing MPs from wastewaters. The effectiveness of different electrode combinations (Fe-Al and Al-Fe), current density (10-20 A/m2), pH (4.0-10.0) and operating times (0-120 min) on the removal of two different polymer particles in water were investigated to obtain maximum treatment efficiency. The effect of pressure (1-3 bar) on membrane filtration removal efficiency was also investigated. The maximum removal efficiencies were obtained as 100% for both polymer types with electrode combination of Al-Fe, initial pH of 7, current density of 20 A/m2 and reaction time of 10 min. The membrane filtration method also displayed a 100% removal efficiency. In addition, these laboratory-scale results were compared with the one-year average data of a plant treating with real-scale membranes. The results indicated that the proposed processes supplied maximum removal efficiency (100%) compared to conventional secondary and tertiary treatment methods (2-81.6%) in the removal of microplastics.

Characterization of littered face masks in the southeastern part of Turkey.

A possible source of microplastics has started to be released into nature because of the single-use face masks that protect us against the spread of COVID-19 and are being thrown onto the streets and into seas and nature. This study aims to estimate the amount of face mask use during the COVID-19 pandemic in Turkey, thereby expressing our concerns about waste management and plastic pollution and calling on appropriate solid waste management policies and governments to take the necessary measures to formulate their strategies at all levels. In this context, the number of masks in an area of 1 km2 in 3 different cities was determined theoretically and experimentally. Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscope (SEM) were also used to evaluate plastic polymer characteristics of the single-use face mask. It was determined that the three cities produce roughly 10 tons of face masks in a day. With the increasing use of single-use plastics, the impact of face masks on microplastic pollution is of great concern. Although studies on the recovery of disposable masks continue, the level is insufficient. Therefore, studies to be carried out on technologies that will enable the repeated use of masks are important.

Treatment of slaughterhouse wastewater by electrocoagulation and electroflotation as a combined process: process optimization through response surface methodology.

The contamination of water with organic compounds has become an increasing concern in today's world. The cost-effective and sustainable treatment of industrial wastewaters is a major challenge. Advanced treatment techniques such as electrocoagulation-electroflotation offer economic and reliable solutions for the treatment of industrial wastewater. In this study, the electrocoagulation-electroflotation method was investigated for the simultaneous removal of chemical oxygen demand, total phosphorus, total Kjeldahl nitrogen, and color via response surface methodology. Factors such as electrode combination (Fe and Al), current density (10-20 mA/cm2), pH (3.0-9.0), and electrode distance (1-3 cm) were investigated in the treatment of wastewater to obtain maximum treatment efficiency. It was determined that chemical oxygen demand, total Kjeldahl nitrogen, total phosphorus, and color removal reached up to 94.0%, 77.5%, 97.0%, and 99.0%, respectively. Treatment costs were found as $0.71 with the Al-Fe electrode combination.

Microplastics composition and load from three wastewater treatment plants discharging into Mersin Bay, north eastern Mediterranean Sea.

Copious quantities of microplastics enter the sewage system on a daily basis, and hence wastewater treatment plants (WWTPs) could be an important source of microplastic pollution in coastal waters. Influent and effluent discharges from three WWTPs in Mersin Bay, Turkey were sampled at monthly intervals over a one-year period during 2017. When data from all WWTPs were combined, fibers constituted the dominant particle form, accounting for 69.7% of total microplastics. Although notable oscillations in microplastic particle concentrations were observed throughout the year influent waters on average contained about 2.5-fold greater concentrations of microplastics compared to the effluent waters. An average of 0.9 microplastic particles were found per liter of effluent from the three WWTPs amounting to around 180 × 106 particles per day to Mersin Bay. This shows that despite their ability to remove 55-97% of microplastics, WWTPs are one of the main sources of microplastics to the northeast Mediterranean Sea.

Operating Cost and Treatment of Boron from Aqueous Solutions by Electrocoagulation in Low Concentration.

The objective of this study is to determine the optimum parameters of electrocoagulation process in treatment of boron in low concentrations. Especially, studies on electrode optimization in low boron concentrated waters are insufficient. Therefore, the effect of electrode combination (Al-Al, Al-Fe, Al-SS, Fe-Al, Fe-Fe, and Fe-SS), pH (5-9), current density (8-24 mA cm-2), distance (1-3 cm), and electrolysis time (10-90 min) on treatment of boron containing wastewater is studied to obtain maximum removal efficiency. The maximum removal efficiency of boron is obtained as 95.6%. Operation conditions for maximum removal are the electrode combination of Fe-Al, current density of 16 mA cm-2, pH 7.0, concentration of 30 mg L-1 and the reaction time of 70 min. Operating cost of the electrocoagulation process is calculated as 2.35 $ m-3. This study indicates that the electrocoagulation process can be successfully applied in order to treat boron-polluted wastewaters at low initial concentrations.

Electrocoagulation and nanofiltration integrated process application in purification of bilge water using response surface methodology.

Marine pollution has been considered an increasing problem because of the increase in sea transportation day by day. Therefore, a large volume of bilge water which contains petroleum, oil and hydrocarbons in high concentrations is generated from all types of ships. In this study, treatment of bilge water by electrocoagulation/electroflotation and nanofiltration integrated process is investigated as a function of voltage, time, and initial pH with aluminum electrode as both anode and cathode. Moreover, a commercial NF270 flat-sheet membrane was also used for further purification. Box-Behnken design combined with response surface methodology was used to study the response pattern and determine the optimum conditions for maximum chemical oxygen demand (COD) removal and minimum metal ion contents of bilge water. Three independent variables, namely voltage (5-15 V), initial pH (4.5-8.0) and time (30-90 min) were transformed to coded values. The COD removal percent, UV absorbance at 254 nm, pH value (after treatment), and concentration of metal ions (Ti, As, Cu, Cr, Zn, Sr, Mo) were obtained as responses. Analysis of variance results showed that all the models were significant except for Zn (P > 0.05), because the calculated F values for these models were less than the critical F value for the considered probability (P = 0.05). The obtained R(2) and Radj(2) values signified the correlation between the experimental data and predicted responses: except for the model of Zn concentration after treatment, the high R(2) values showed the goodness of fit of the model. While the increase in the applied voltage showed negative effects, the increases in time and pH showed a positive effect on COD removal efficiency; also the most effective linear term was found as time. A positive sign of the interactive coefficients of the voltage-time and pH-time systems indicated synergistic effect on COD removal efficiency, whereas interaction between voltage and pH showed an antagonistic effect.