مجله آب و فاضلاب
پیاپی 139 (خرداد و تیر 1401)

High levels of iron and manganese in drinking water cause sediment, turbidity, bad taste and color. As there is a wide area of rice and tea under cultivation in Guilan province with an inevitable production of waste from them, it is possible to use it for removal of undesirable elements. The present study was discontinuously performed on a laboratory scale. The impact of important factors such as pH, contact time, initial concentration, adsorbent dosage and temperature were investigated. Also, using group method of data handling, the adsorption process of the batch method was modeled. The results showed that the highest iron adsorption capacity (in terms of mg/g) for tea leaves and rice straw were 19.44 and 19.99, respectively. Considering manganese, it was 19.86 for tea leaves and 19.49 for rice straw. The best conditions for removing iron and manganese from aqueous solution are at neutral pH, contact time 40-50 minutes, absorbent dose 0.05 g and temperature 25-35 °C for tea leaves and rice straw. Overall, the GMDH model performs better in predicting the final concentrations of iron and manganese in water sources. In general, it can be concluded that rice straw and tea leaves can be used as inexpensive and environmentally friendly natural absorbers in the removal of iron and manganese from water sources.

Today, antibiotics are known as one of the major environmental pollutants, particularly of water, due to their widespread use, toxicity, causing drug resistance and their lasting effects. This study was designed to evaluate the efficiency of the advanced oxidation process of sodium monopersulfate activated with steel industry slag in the presence of ultraviolet rays aimed at eliminating the tetracycline antibiotic from aqueous and effluent media. We examined the effect of the variables of pH, solution temperature, reaction time, initial concentration of antibiotics, sodium monopersulfate concentration, and the UV ray intensity on the process efficiency. A high-performance liquid chromatography machine was used to measure the concentration of the tetracycline antibiotic. According to the study results, under optimal and certain conditions (sodium monopersulfate: 2 mM, pH: 2, iron ions level in the steel industry slag: 0.4 g/L, UV intensity: 8 watts) and during 60 minutes, the elimination efficiency rates of tetracycline antibiotic, COD, and TOC were obtained as 98%, 61.8%, and 48.9%, respectively, with a mineralization level higher than 55%. The rate of tetracycline antibiotic removal was directly related to the concentrations of iron ions, sodium monopersulfate, UV intensity, and the temperature, while increasing the pH from 2 to 10 decreased the process efficiency from 98% to 46%; and enhancing the initial concentration of tetracycline antibiotic from 5 to 50 mg/L also reduced the removal rate of the antibiotic from 86% to 47%. The research revealed that the advanced oxidation process of sodium monopersulfate activated by steel industry slag in the presence of ultraviolet rays can be used as a proper method with effective efficiency to eliminate the high concentration of antibiotics found in a real sewage sample.

Cefazolin is a widely used antibiotic in the treatment of bacterial infections that enters the water sources in original or metabolized form through the discharge of sewage and effluents. The presence of antibiotics in the environment can affect non-target pathogens, change the structure, enrich the algae in water sources, interfere with photosynthesis in plants and cause morphological abnormalities in plants. Various methods have been studied to remove antibiotics. Among these, surface adsorption is one of the appropriate methods. Therefore, in this study, the synthesis of polyaniline-polyethylene glycol resin and its evaluation in the removal of cefazolin by the adsorption process were investigated. Polyanyylene-polyethylene glycol resin was prepared by chemical polymerization method. Transfer electron microscope, thermometer and infrared spectrometer were used to determine the properties of the synthesized resin. In this study, the effect of pH parameters in the range of 2 to 8, the amount of adsorbent 0.1 to 5 g, the initial concentration of antibiotics in the amount of 10 to 100 mg/L, contact time 15 to 120 minutes and the temperature range of 20 to 70 °C, adsorbent desorption with nitric acid and sodium hydroxide, the interfering compounds of chloride and sulfate were investigated. The adsorption isotherms of Langmuir, Freundlich, Tamkin and adsorption kinetics were determined. In all stages, spectrophotometer was used to determine the concentration of cefazolin and HPLC was used to determine the effect of interfering ions on the removal of cefazolin and to confirm the results of spectra to determine the effect of interfering ions. The contact time of 60 minutes of adsorbent and cefazolin was selected as the optimal time due to the completion of the adsorption capacity of polyaniline-polyethylene glycol resin and high removal efficiency. Due to the high removal efficiency of cefazolin at (pH = 5), cefazolin was selected as the optimal pH due to the competition between OH- ions and negatively charged molecules. Adsorbent (3 g) was selected as the optimal adsorbent due to the increase in removal efficiency with increasing adsorbent consumption and the presence of a large number of adsorption sites. Elimination of cefazolin was tested in the concentration range (10, 20, 50, 70 and 100 mg/L) and the results showed that with increasing the concentration of cefazolin, the removal efficiency decreased from 69% to 50% due to more adsorption sites on the adsorbent surface in concentrations. Low concentration of cefazolin causes to be rapidly absorbed and the removal efficiency increases. The results of experiments of the effect of disturbing compounds showed that the removal percentage of cefazolin in distilled water from 98.46% to 72.72% in municipal water despite the disturbing compounds of chloride and sulfate due to the formation of anions with the adsorbent surface and the formation of stable complexes and barriers to cefazolin uptake decreased. The results of adsorbent reduction showed that the percentage of removal of cefazolin after 6 steps by nitric acid decreased from 93.99 to 74.55% and decreased by profit from 41.25 to 21.56%.

Wastewater treatment unit in an oil refinery is one of the main emission sources of volatile organic compounds and exposure to these pollutants has major negative impacts on refinery staff and residents of adjacent areas. The purpose of this study is to investigate the concentration of volatile organic compounds in refinery effluents and to estimate the emission of these compounds into the air. Concentration and pollution load of volatile organic compounds in operating units and basins of treatment unit wastewater were analyzed using gas chromatography and emission estimation of them was done using the Rank 2 and Rank 3 of the US Environmental Protection Agency. The pollution received by wastewater plant was 1095 ton/y of five components: benzene, toluene, xylene, ethyl benzene and hexane, while 5379 ton/y for the eleven pollutants including previous five components plus pentane, heptane, methyl cyclohexane, 1-2-4 tri-methylbenzene, 1-3-5 tri-methylbenzene and dodecane. Based on refinery feed, for each ton of crude oil processed, 187 g of the total 5 compounds and 692 g of 11 compounds are produced from operational units; but only 78% of the 11 compounds and 60% of the 5 compounds could reach the treatment unit, which indicates the emission of pollutants in the transfer path. Overall, for each ton of processed crude oil, 48.5 g of 5 compounds and 241.6 g of 11 compounds from effluent treatment ponds are emitted to the atmosphere. Identifying the sources of volatile organic compounds production is one of the ways to reduce the pollution load entering the treatment unit and thus reduces the emission from the refinery. Based on these results, refineries could apply proper strategies for emission decrease. This research has been done for a refinery with ten megatons capacity per year and medium complexity, which could be used by any analogous refinery in the world.

The use of unconventional water sources, such as the reuse of treated wastewater in accordance with environmental principles, is of great importance. The aim of this study was to investigate the effect of artificial wetland treatment of Qasr-e-shirin in Kermanshah province on water quality, growth performance and biochemical composition of fish body for optimal use in the aquaculture industry. In this study, water quality parameters including turbidity, DO, COD, MPN total coliform, nitrate, phosphate, and experiments in sections of bioassay, monitoring of aquatic tissue due to the presence of pathogens were satisfactory.The results show that the COD, turbidity and MPN values of the total effluent from the treatment plant are 33 mg/L, 13.4 NTU and 230,000, respectively. Effluent analysis took place after passing through the UV pool and complete dewatering of the pool with treated and disinfected effluent; COD, turbidity and MPN values of total coliform were 25 mg/L, 13 NTU and 8000, respectively. The microbial load of the effluent is dramatically reduced by passing through the UV pool. The bioassays performed confirmed the proper growth of aquatic animals during the growth process and had a high and appropriate index; also, according to microbiological tests, no traces of human-borne microbes were observed in fish tissue. According to the national standards and the results of the analysis of the output of the treatment and disinfection unit, it is observed that in the current conditions and treatment system, it is not possible to use this treated wastewater for fish farming in the region and more treatment is needed.

Landfills can be considered as a potential threat to groundwater resources, considering the potential of groundwater pollution by leachate with the pollutants such as hydrocarbons and heavy metals. In this study, spatial changes in groundwater quality used in agriculture, in the vicinity of landfill site of municipal solid wastes in the southwest of Zanjan city were investigated. For this purpose, analysis of 18 physicochemical, heavy metals and bacterial parameters in leachate and 14 groundwater samples were investigated around the dumpsite up to a 5 km radius from landfill during two sampling periods (i.e., December 2020 and June 2011). In this study, several indices including leachate pollution index, sodium absorption ratio, Killie index, soluble sodium percentage and permeability index were used to investigate groundwater pollution in the study area due to leachate or other sources. According to the results of LPI, none of the groundwater samples were polluted with leachate. Also, the quality of these resources for use in agriculture was evaluated favorably according to SAR, KR and PI indices, however, according to SSP, 64% and 86% of samples during December 2020 and June 2021, respectively, were reported polluted. In general, the results of qualitative study of groundwater samples in dry season (December 2020) were more pronounced than pollutants. Although based on the results of agricultural indicators and LPI in well number 5 as the closest well to the landfill, no contamination by leachate has been reported, however the high chlorine concentration which was at maximum of allowed range, the potential dangers of landfill leachate were shown. It is noted that chlorine acts as a leachate detector in groundwater. Therefore it is recommended that monitoring wells be dug at different depths and at distances of less than one kilometer from the landfill, and sampling be done in successive periods to determine even the smallest effects of leachate on groundwater.

What is important in the current situation it is important to pay attention to patterns of the water consumption behavior of subscribers and to identify subscribers and consumers with a higher position in the value pyramid in the field of water consumption management policy. Value pyramid is a tool that identifies valuable customers in terms of consumption, and so, has great application and importance in the field of water consumption management to identify high-consumption and low-consumption customers. Therefore, in the present study, in order to identify the patterns of consumption behavior of Shiraz Water and Wastewater Company subscribers based on their consumption value pyramid and to predict the subscribers with a higher position in the value pyramid, data mining techniques have been used. In the framework of the proposed method, first, the data of water subscribers' consumption including residential, commercial and industrial subscribers, public and administrative, religious and educational sites, military and non-governmental, for two consecutive years, were extracted from the database of Shiraz Water and Wastewater Company. After determining the optimal number of clusters using self-organizing map and Davis Bouldin index, clustering operation is performed using K-Means algorithm. It should be noted that the indicators and criteria for subscriber clustering include the type of use, location, consumption, history of unauthorized branching, number of disconnection notices and time of payment of bills which have been identified using the opinion of experts. Then, while calculating the consumption value of subscribers in each cluster and plotting the subscriber consumption value pyramid, the decision tree algorithm is used to predict and discover the behavioral patterns of subscribers. The results show that Shiraz Water and Wastewater Company subscribers are divided into six clusters in terms of consumption behavior patterns. While drawing the consumption value pyramid, these six clusters are classified into three classes: high consumption subscribers, medium consumption subscribers and low consumption subscribers. After implementing the decision tree, the accuracy of the tree was 78.92 that, according to the results of the decision tree, the subscribers of these three classes have 11 patterns of behavior that predict the type of consumption. Thus, according to the 11 behavioral patterns of the subscribers of Shiraz Water and Wastewater Company, the consumption of new subscribers can be predicted and its position in the value pyramid can be determined.

Municipal wastewater treatment and algal biomass production are simultaneously new and efficient methods in the treatment industry. Using artificial culture medium, urban wastewater is used as a food source for microalgae. Cultivation of microalgae in wastewater is an important step in wastewater treatment that, in addition to wastewater treatment, simultaneous production of biomass is done which can be used for many purposes and is of great value. in the present study, the effect of initial pH on the performance of membrane photobioreactor in biomass growth and nutrient removal from municipal wastewater was investigated. In this study, first Chlorella vulgaris microalgae in a membrane optical bioreactor with a light intensity of 300 μmol photons m-2. s-1 in the 24-hour light cycle and an initial concentration of 1 g/L dry weight of microalgae in the initial three pH (4, 7 and 10) were cultivated. Then, due to the direct relationship between microalgae growth and nutrient removal, the best initial pH in nitrate and phosphate removal from municipal wastewater was investigated. According to the results, microalgae were adapted to municipal effluent after 9 days and at the initial pH of 7, the highest growth rate of microalgae equal to 2.37 g dry weight per liter, and removal of nitrate and phosphate were 88 and 87%, respectively. Also, on the 15th day at the same initial pH, the highest amount of nitrate and phosphate removal from municipal effluent was 92% and 91%, respectively. The results show that the regulation of the initial pH of microalgae can have an undeniable effect on the growth of microalgae. It also has a significant effect on the removal of nitrate and phosphate from municipal wastewater through the cultivation of microalgae. By optimizing the initial pH, this removal percentage has increased.

The present study investigates the effects of recirculation on the leachate pollutions and biogas production in a waste processing in the west of Tehran province, Iran. Recirculation is considered as an effective way in leachate pollutants reduction and biogas production rate increase. For this purpose, a trench with a size of 3*3*2.5 m was dug, and one pipe was applied for sampling.  Parameters were examined, including the chemical oxygen demand, biochemical oxygen demand, turbidity, total suspended solids, ammonium, phosphate, copper, iron, cadmium, lead, and zinc. To evaluate the production of gases, the periodical measurements of CH4, H2S, and SO2 were performed. Moreover, biogas production in the trench was measured in seven repetitions. Then, leachate recirculation in the landfill was performed at the leachate volume ratio of 20:1, 10:1, 5:1, and 40:1. Comparison of the results indicated that the recirculation volume ratio of 1:20 maximized the reduction of pollutants. At this volume ratio, the maximum productions of CH4, H2S, and SO2 were obtained to be 50127 ppm, 21.12 ppm, and 0.23 ppm, respectively. The recirculation at the ratio of 20:1 reduced COD, BOD, ammonium, phosphate, TSS, and turbidity by 1650 mg/L (26%), 889 mg/L (20%), 1650 mg/L (26%), 10 mg/L (23%), 63 mg/L (11%), and 11.2 NTU (23%), respectively. Although the effects of recirculation on the reduction of pollutants, particularly organic ones, were found to be satisfactory, complementary treatment is required for the secondary utilization of wastewater.

In the face of growing water demand and insufficient public budgets in developing countries, public-private partnerships play an important role in infrastructure development, such as water supply and transmission. However, carrying out such projects always carries with it many and varied risks that threaten the success of such projects. Due to the research gap on risk identification and assessment in the context of public-private partnership water transfer projects, the purpose of the present research is to identify and prioritize the risks in Safadasht public-private partnership water transfer project. The first phase of the present research identifies the risks of public-private partnership projects. At this stage of the research, through the brainstorming method, an attempt was made to identify the risks related to the project under study. In the second stage, three research criteria including "probability of occurrence", "cost effect" and "time effect" were weighed using the best-worst method. The third stage, which was the final stage of the research, was dedicated to prioritizing the risks identified in the first stage using the simple additive weighting technique. Based on the analyzes performed, respectively, changes in legal conditions and standards by the government, sudden changes in bank interest rates, severe climate change, damage to the investor's manpower and improper performance of the investor project factors were identified as the most important risks. Finally, while pointing out the limitations of the research, some suggestions for future studies were presented.