The flow pattern effects of hydrodynamic cavitation on waste activated sludge digestibility.

The disintegration of raw sludge is of importance for enhancing biogas production and facilitates the degradation of substrates for microorganisms so that the efficiency of digestion can be increased. In this study, the effect of hydrodynamic cavitation (HC) as a pretreatment approach for waste activated sludge (WAS) was investigated at two upstream pressures (0.83 and 1.72 MPa) by using a milli-scale apparatus which makes sludge pass through an orifice with a restriction at the cross section of the flow. The HC probe made of polyether ether ketone (PEEK) material was tested using potassium iodide solution and it was made sure that cavitation occurred at the selected pressures. The analysis on chemical effects of HC bubbles collapse suggested that not only cavitation occurred at low upstream pressure, i.e., 0.83 MPa, but it also had high intensity at this pressure. The pretreatment results of HC implementation on WAS were also in agreement with the chemical characterization of HC collapse. Release of soluble organics and ammonium was observed in the treated samples, which proved the efficiency of the HC pretreatment. The methane production was improved during the digestion of the treated samples compared to the control one. The digestion of treated WAS sample at lower upstream pressure (0.83 MPa) resulted in higher methane production (128.4 mL CH4/g VS) compared to the treated sample at higher upstream pressure (119.1 mL CH4/g VS) and control sample (98.3 mL CH4/g VS). Thus, these results showed that the HC pretreatment for WAS led to a significant increase in methane production (up to 30.6%), which reveals the potential of HC in full-scale applications.

Impact of food waste addition in energy efficient municipal wastewater treatment by aerobic granular sludge process.

Recently, one of the main purposes of wastewater treatment plants is to achieve a neutral or positive energy balance while meeting the discharge criteria. Aerobic granular sludge (AGS) technology is a promising technology that has low energy and footprint requirements as well as high treatment performance. The effect of co-treatment of municipal wastewater and food waste (FW) on the treatment performance, granule morphology, and settling behavior of the granules was investigated in the study. A biochemical methane potential (BMP) test was also performed to assess the methane potential of mono- and co-digestion of the excess sludge from the AGS process. The addition of FW into wastewater enhanced the nutrient treatment efficiency in the AGS process. BMP of the excess sludge from the AGS process fed with the mixture of wastewater and FW (195 ± 17 mL CH4/g VS) was slightly higher than BMP of excess sludge from the AGS process fed with solely wastewater (173 ± 16 mL CH4/g VS). The highest methane yield was observed for co-digestion of excess sludge from the AGS process and FW, which was 312 ± 8 mL CH4/g VS. Integration of FW as a co-substrate in the AGS process would potentially enhance energy recovery and the quality of effluent in municipal wastewater treatment.

Modelling of high-rate activated sludge process: Assessment of model parameters by sensitivity and uncertainty analyses.

The objective of this study is to develop a mechanistic model to predict the long-term dynamic performance of High-Rate Activated Sludge (HRAS) process, including the removal of carbon (COD), nitrogen (N), and phosphorus (P). The model was formulated with inspiration from Activated Sludge Models No. 1 and 3 (ASM1 and ASM3) to incorporate essential mechanisms, such as adsorption and storage substrate, specific to HRAS systems. A stepwise protocol was followed for calibration with dynamic data from a pilot-scale HRAS plant. Sensitivity analysis identified influential model parameters, including maximum specific growth rate (µ), growth yield (YH), storage yield (YSTO), storage rate (kSTO), decay rate (b), and half saturation of the readily biodegradable substrate for growth (KS1). The calibrated model achieved prediction efficiencies above the normalized Mean Absolute Error (MAE) of 70 % for mixed liquor suspended solids (MLSS), total chemical oxygen demand (TCOD), soluble COD (SCOD), particulate COD (XCOD), total nitrogen (TN), ammonia nitrogen (SNH), total phosphorus (TP), soluble TP (STP), and particulate TP (XTP). Uncertainty analysis revealed that SCOD was underestimated. Based on the dynamic profiles of uncertainty bands and observed data, there is potential for improving the estimation of dynamic behavior in STP. The observed discrepancies may be attributed to variations in wastewater characteristics during the monitoring period, particularly concerning the phosphorus (P) fractions of the readily biodegradable substrate (SS) and soluble inerts (SI), which were not considered as dynamically changing parameters in the model.

Environmental impact of sewage sludge co-digestion with food waste and fat-oil-grease: Integrating plant-wide modeling with life cycle assessment approach.

Anaerobic co-digestion of fat-oil-grease (FOG) and food waste (FW) with sewage sludge (SS) in wastewater treatment plants is a method used to increase biogas production. In this study, digestion scenarios were compared using plant-wide modeling and life cycle assessment: Scenario-0 (mono-digestion of waste-activated sludge (WAS)), Scenario-1 (co-digestion of WAS with FOG), and Scenario-2 (co-digestion of WAS with FW). Scenario-0, with the highest energy use and landfilling of FOG/FW, has the worst environmental impact. Scenario-1 and Scenario-2 minimize the environmental load by energy recovery and avoiding landfilling of organic waste. Scenario-wise, the change in greenhouse gas (GHG) emissions from treatment was negligible. However, due to the impact of landfilling, GHG emissions in Scenario-0 were 21% and 30% higher than in Scenario-1 and 2, respectively. The environmental benefit of anaerobic co-digestion of FOG/FW with SS is not only in the contribution to energy production but also in the recycling of organic waste.

Use of water treatment plant sludge in high-rate activated sludge systems: A techno-economic investigation.

Coagulants such as aluminum sulfate (Al2(SO4)3 (alum)) and ferric chloride (FeCl3) used in water treatment plants (WTPs) led to the generation of sludge that is usually disposed to landfills. However, the utilization of WTP sludge is being encouraged by authorities to achieve sustainable development. This study aims to investigate WTP sludge utilization in a pilot-scale high-rate activated sludge (HRAS) system as a substitute for conventional coagulants. Based on jar tests, the iron sludge was selected for pilot-scale testing due to its superior ability to enhance the treatment efficiency of the HRAS process compared to alum sludge. Iron sludge addition (20.1 ± 1.6 mg dry sludge/L wastewater) slightly improved the removal efficiency of particulate chemical oxygen demand (pCOD) from 74 % to 81 % (p-value: 0.014). Iron sludge addition had a distinct effect on the sludge characteristics of the HRAS process. The average median particle size (d50) increased from 96 ± 3 to 163 ± 14 µm (p-value<0.00) with the addition of iron sludge, which improved the settleability of the HRAS process sludge. However, the biochemical methane potential (BMP) of the HRAS process sludge decreased by 8.9 % (p-value<0.00) after iron sludge addition. In a scenario analysis of WTP sludge use in a hypothetical HRAS plant, the effluent quality index (EQI), an indicator of environmental impact, was calculated and the cost related to the operation (the transfer and landfill disposal of WTP and HRAS process sludge, energy and chemical consumption of the HRAS plant) was estimated. As a result, using WTP sludge in the HRAS plant did not significantly affect the EQI of the plant but decreased overall cost by 11 %. The results showed that the use of WTP sludge as a coagulant in wastewater treatment could achieve mutual benefits for WTPs and WWTPs and have the potential to realize the circular economy model.

Impact of primary treatment methods on sludge characteristics and digestibility, and wastewater treatment plant-wide economics.

Biogas production from anaerobic sludge digestion plays a central role for wastewater treatment plants to become more energy-efficient or even energy-neutral. Dedicated configurations have been developed to maximize the diversion of soluble and suspended organic matter to sludge streams for energy production through anaerobic digestion, such as A-stage treatment or chemically enhanced primary treatment (CEPT) instead of primary clarifiers. Still, it remains to be investigated to what extent these different treatment steps affect the sludge characteristics and digestibility, which may also impact the economic feasibility of the integrated systems. In this study, a detailed characterization has been performed for sludge obtained from primary clarification (primary sludge), A-stage treatment (A-sludge) and CEPT. The characteristics of all sludges differed significantly from each other. The organic compounds in primary sludge consisted mainly of 40% of carbohydrates, 23% of lipids, and 21% of proteins. A-sludge was characterized by a high amount of proteins (40%) and a moderate amount of carbohydrates (23%), and lipids (16%), while in CEPT sludge, organic compounds were mainly 26% of proteins, 18% of carbohydrates, 18% of lignin, and 12% of lipids. The highest methane yield was obtained from anaerobic digestion of primary sludge (347 ± 16 mL CH4/g VS) and A-sludge (333 ± 6 mL CH4/g VS), while it was lower for CEPT sludge (245 ± 5 mL CH4/g VS). Furthermore, an economic evaluation has been carried out for the three systems, considering energy consumption and recovery, as well as effluent quality and chemical costs. Energy consumption of A-stage was the highest among the three configurations due to aeration energy demand, while CEPT had the highest operational costs due to chemical use. Energy surplus was the highest by the use of CEPT, resulting from the highest fraction of recovered organic matter. By considering the effluent quality of the three systems, CEPT had the highest benefits, followed by A-stage. Integration of CEPT or A-stage, instead of primary clarification in existing wastewater treatment plants, would potentially improve the effluent quality and energy recovery.

Nutrient recovery from municipal solid waste leachate in the scope of circular economy: Recent developments and future perspectives.

Holistically considering the current situation of the commercial synthetic fertilizer (CSF) market, recent global developments, and future projection studies, dependency on CSFs in agricultural production born significant risks, especially to the food security of foreign-dependent countries. The foreign dependency of countries in terms of CSFs can be reduced by the concepts such as the circular economy and resource recovery. Recently, waste streams are considered as a source in order to produce recovery-based fertilizers (RBF). RBFs produced from different waste streams can be substituted with CSFs as input for agricultural applications. Municipal solid waste leachate (MSWL) is one of the waste streams that have a high potential for RBF production. Distribution of the published papers over the years shows that this potential was noticed by more researchers in the millennium. MSWL contains a remarkable amount of nitrogen and phosphorus which are the main nutrients required for agricultural production. These nutrients can be recovered with many different methods such as microalgae cultivation, chemical precipitation, ammonia stripping, membrane separation, etc. MSWL can be generated within the different phases of municipal solid waste (MSW) management. Although it is mainly composed of landfill leachate (LL), composting plant leachate (CPL), incineration plant leachate (IPL), and transfer station leachate (TSL) should be considered as potential sources to produce RBF. This study compiles studies conducted on MSWL from the perspective of nitrogen and phosphorus recovery. Moreover, recent developments and limitations of the subject were extensively discussed and future perspectives were introduced by considering the entire MSW management. Investigated studies in this review showed that the potential of MSWL to produce RBF is significant. The outcomes of this paper will serve the countries for ensuring their food security by implementing the resource recovery concept to produce RBF. Thus, the risks born with the recent global developments could be overcome in this way besides the positive environmental outcomes of resource recovery.

One-stage anaerobic fermentation of excess sludge for caproate production by supplementing chain elongation enrichments with ethanol as electron donor.

Medium chain fatty acids (MCFAs) production from excess sludge have recently received great research interest due to higher energy densities, easy-separation capability and high economic benefits. Here, the addition of chain elongation (CE) enrichments with ethanol as electron donor was used to enhance caproate production from one-stage sludge fermentation. Compared with 0.20 g/L of controls, caproate production reached 9.00 g/L by supplementing CE enrichments with ethanol/acetate ratio of 3:1 after 7 days of acidification of organic matter in pretreated sludge fermentation. Clostridium_sensu_stricto_12, that refers to CE, was enriched in the first and second transfer of the sludge microbial consortium. Maintaining the stability of the microbial consortium would be the key that enables stable and efficient caproate production from sludge fermentation by supplementing CE enrichments.

Coupling high-rate activated sludge process with aerobic granular sludge process for sustainable municipal wastewater treatment.

Achieving a neutral/positive energy balance without compromising discharge standards is one of the main goals of wastewater treatment plants (WWTPs) in terms of sustainability. Aerobic granular sludge (AGS) technology promises high treatment performance with low energy and footprint requirement. In this study, high-rate activated sludge (HRAS) process was coupled to AGS process as an energy-efficient pre-treatment option in order to increase energy recovery from municipal wastewater and decrease the particulate matter load of AGS process. Three different feeding strategies were applied throughout the study. AGS system was fed with raw municipal wastewater, with the effluent of HRAS process, and with the mixture of the effluent of HRAS process and raw municipal wastewater at Stage 1, Stage 2 and Stage 3, respectively. Total suspended solids (TSS), chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total phosphorus (TP) concentrations in the effluent were less than 10 mg/L, 60 mg/L, 0.4 mg/L, and 1.3 mg/L respectively at all stages. Fluctuations were observed in the denitrification performance due to changes in the influent COD/total nitrogen (TN) ratio. This study showed that coupling HRAS process with AGS process by feeding the AGS process with the mixture of HRAS process effluent and raw municipal wastewater could be an appropriate option for both increasing the energy recovery potential of WWTPs and enabling high effluent quality.

Enhanced visible-light driven photocatalytic degradation of bisphenol A by tuning electronic structure of Bi/BiOBr.

Visible-light (VL) photocatalysis has been regarded as an intriguing technology for the control of persistent environmental pollutants. In this study, the novel homogeneous Co doped-Bi/BiOBr nanocomposites (CB-X) were prepared via a facile one-step hydrothermal method, featured with a uniform 0D Bi nanodots distribution on 2D Co-doped BiOBr nanosheets, and the photocatalytic performance was evaluated by decomposing the BPA as a prototype contaminant. The degradation experiment indicated that the optimal CB-2 nanocomposite exhibited the best photocatalytic activity with a 94% removal efficiency of BPA under the VL irradiation of 30 min; And the corresponding apparent rate constant (k) was as high as 0.107 min-1, which was 10.7 times greater than that of Bi/BiOBr (0.010 min-1). Benefiting from the modulation effect of Co-doping on the intrinsic electron configuration of Bi/BiOBr, the elevated VL adsorption capacity and accelerated h+/e- pairs separation rate were achieved, which were evidenced by photoluminescence (PL) spectroscopy, photo-electrochemical measurements and density functional theory (DFT) calculation. Moreover, the major reactive species in CB-X/VL system were uncovered to be •O2- and 1O2, whereas •OH and h+ presented a secondary contribution in the BPA elimination. Finally, the possible photocatalytic mechanism involved in CB-X nanocomposites and BPA degradation pathways were proposed on the basis of the various intermediates and products detected by LC-MS/MS.

Antiviral drugs against influenza: Treatment methods, environmental risk assessment and analytical determination.

Over the past few years, antiviral drugs against influenza are considered emerging contaminants since they cause environmental toxicity even at low concentrations. They have been found in environmental matrices all around the world, showing that conventional treatment methods fail to remove them from water and wastewater. In addition, the metabolites and transformation products of these drugs can be more persistent than original in the environment. Several techniques to degrade/remove antiviral drugs against influenza have been investigated to prevent this contamination. In this study, the characteristics of antiviral drugs against influenza, their measurement by analytical methods, and their removal in both water and wastewater treatment plants (WWTPs) were presented. Different treatment methods, such as traditional procedures (biological processes, filtration, coagulation, flocculation, and sedimentation), advanced oxidation processes (AOPs), adsorption and combined methods, were assessed. Ecotoxicological effects of both the antiviral drug and its metabolites as well as the transformation products formed as a result of treatment were evaluated. In addition, future perspectives for improving the removal of antiviral drugs against influenza, their metabolites and transformation products were further discussed. The research indicated that the main tested techniques in this study were ozonation, photolysis and photocatalysis. Combined methods, particularly those that use renewable energy and waste materials, appear to be the optimum approach for the treatment of effluents containing antiviral drugs against influenza. In light of high concentrations or probable antiviral resistance, this comprehensive assessment suggests that antiviral drug monitoring is required, and some of those substances may cause toxicological effects.

Impact of primary sedimentation on granulation and treatment performance of municipal wastewater by aerobic granular sludge process.

Aerobic granules contain microorganisms that are responsible for carbon, nitrogen, and phosphorus removal in aerobic granular sludge (AGS) process in which aerobic/anoxic/anaerobic layers (from surface to core) occur in a single granule. Optimizing the aerobic granular sludge (AGS) process for granulation and efficient nutrient removal can be challenging. The aim of this study was to examine the impact of settling prior to AGS process on granulation and treatment performance of the process. For this purpose, synthetic wastewater mimicking municipal wastewater was fed directly (Stage 1), and after primary sedimentation (Stage 2) to a laboratory-scale AGS system. In full-scale wastewater treatment plants, primary sedimentation is used to remove particulate organic matter and produce primary sludge which is sent to anaerobic digesters to produce biogas. Performances obtained in both stages were compared in terms of treatment efficiency, granule settling behavior, and granule morphology. Granulation was achieved in both stages with more than 92% chemical oxygen demand (COD) removal efficiencies in each stage. High nutrient removal was obtained in Stage 1 since anaerobic phase was long enough (i.e., 50 min) to hydrolyze particulate matter to become available for PAOs. Primary sedimentation caused a decrease in influent organic load and COD/N ratio, as a result, low nitrogen and phosphorus removal efficiencies were observed in Stage 2 compared to Stage 1. With this study, the effect of the primary sedimentation on the biological removal performance of AGS process was revealed. COD requirement for nutrient removal in AGS systems should be assessed by considering energy generation via biogas production from primary sedimentation sludge.

Nanomaterials in membrane bioreactors: Recent progresses, challenges, and potentials.

The use of nanomaterials (NMs) in the fabrication and modification of membranes as well as the coupling of nanomaterial-based processes with membrane processes have been attracted many researchers today. The NMs due to a wide range of types, different chemistry, the possibility of various kinds of functionality, different properties like antibacterial activity, hydrophilicity, and large surface area were applied to enhance the membrane properties. In the membrane bioreactors (MBRs) as a highly successful process of membrane technology in wastewater treatment, the NMs have been applied for improving the efficiency of MBR process. This review assessed the application of NMs both as the modifiers of membrane and as the effective part of hybrid techniques with MBR system for wastewater treatment. The efficiency of NMs blended membranes in the MBR process has been reviewed in terms of antifouling and antibacterial improvement and removal performance of the pollutants. Novel kinds of NMs were recognized and discussed based on their properties and advantages. The NMs-based photocatalytic and electrochemical processes integrated with MBR were reviewed with their benefits and drawbacks. In addition, the effect of the presence of mobilized NPs in the sludge on MBR performance was surveyed. As a result of this review, it can be concluded that nanomaterials generally improve MBR performance. The high flux and antifouling properties can be obtained by adding nanomaterials with hydrophilic and antibacterial properties to the membrane, and further studies are required for photocatalytic NMs applications. In addition, this review shows that the low amounts of NMs in the membrane structure could have an effective influence on the MBR process. Besides, since many studies in the literature are carried out at the laboratory scale, it is thought that pilot and real-scale studies should be carried out to obtain more reliable data.

Primary and A-sludge treatment by anaerobic membrane bioreactors in view of energy-positive wastewater treatment plants.

Energy-rich sludge can be obtained from primary clarifiers preceding biological reactors. Alternatively, the incoming wastewater can be sent to a very-high-loaded activated sludge system, i.e., a so-called A-stage. However, the effects of applying an A-stage instead of a primary clarifier, on the subsequent sludge digestion for long-term operation is still unknown. In this study, biogas production and permeate quality, and filterability characteristics were investigated in a lab-scale anaerobic membrane bioreactor for primary sludge and A-stage sludge (A-sludge) treatment. A higher specific methane yield was obtained from digestion of A-sludge compared to primary sludge. Similarly, specific methanogenic activity was higher when the anaerobic membrane bioreactor was fed with A-sludge compared to primary sludge. Plant-wide mass balance analysis indicated that about 35% of the organic matter in wastewater was recovered as methane by including an A-stage, compared to about 20% with a primary clarifier.

Removal of micropollutants from municipal wastewater by membrane bioreactors: Conventional membrane versus dynamic membrane.

In this study, fate of micropollutants was investigated in a membrane bioreactor (MBR) having dynamic membrane (DM) and ultrafiltration (UF) membrane for the treatment of raw municipal wastewater. Removal efficiencies of different micropollutants including sulfamethoxazole, ciprofloxacin, trimethoprim, caffeine and acetaminophen were assessed. A commercial hollow fiber UF membrane was used in parallel with a DM that was formed on a low-cost hollow fiber support material, made of polyester. MBR was operated at a flux of 10 L/m2·h. High total suspended solids (>99%) and chemical oxygen demand (>91%) removal efficiencies were achieved with each membrane. Besides, high removal efficiencies of micropollutants (>68.3->99.7%) were achieved. Morphological analyses were conducted for each membrane in order to get insight to the cake (dynamic) layer that was accumulated on the membrane. DM technology provides an effective alternative to the conventional membrane systems for micropollutant removal from municipal wastewater.

Comparative evaluation of ultrafiltration and dynamic membranes in an aerobic membrane bioreactor for municipal wastewater treatment.

This study investigated the applicability of self-forming hollow fiber dynamic membrane (DM) as a low-cost alternative to ultrafiltration (UF) membrane. A hollow fiber polyester fabric was used as a support material to form the DM layer. Submerged DM and UF hollow fiber membrane were placed in the same reactor in order to compare the treatment and filtration performance of each membrane. Morphological analyses were also carried out for DM surface. The system was operated continuously at a flux of 5 L/m2 h for 85 days. High COD removal efficiency and total suspended solids (TSS) rejection were achieved by the DM. Transmembrane pressure (TMP) of the DM was higher in comparison to the UF membrane, which was related with the formation of cake layer in DM. DM technology can be used as an alternative to UF membrane for municipal wastewater treatment.

High-rate activated sludge processes for municipal wastewater treatment: the effect of food waste addition and hydraulic limits of the system.

Conventional activated sludge (CAS) process is one of the most commonly applied processes for municipal wastewater treatment. However, it requires a high energy input and does not promote energy recovery. Currently, high-rate activated sludge (HRAS) process is gaining importance as a good option to reduce the energy demand of wastewater treatment and to capture organic matter for valorizing through anaerobic digestion (AD). Besides, food waste addition to wastewater can help to increase the organic matter content of wastewater and thus, energy recovery in AD. The objective of this study is to evaluate the applicability of co-treatment of municipal wastewater and food waste in a pilot-scale HRAS system as well as to test the minimal hydraulic retention times (HRTs) such as 60 and 30 min. Food waste addition to the wastewater resulted in a 10% increase in chemical oxygen demand (COD) concentration of influent. In the following stages of the study, the pilot-scale system was operated with wastewater solely under the HRTs of 60 and 30 min. With the decrease of HRT, particulate COD removal increased; however, soluble COD removal decreased. The results demonstrated that if the settling process is optimized, more particulate matter can be diverted to sludge stream.

Anaerobic Digestion Model No. 1 (ADM1) for mathematical modeling of full-scale sludge digester performance in a municipal wastewater treatment plant.

Anaerobic digestion of sludge is considered to be one of the most appropriate technologies for energy production via conversion of organic matter into methane containing biogas. Biogas produced by anaerobic digestion of municipal wastewater sludge can be utilized as fuel to offset heat and electricity consumption of wastewater treatment facilities. Modeling can be used effectively to evaluate the impact of different process and operation variables on the performance of the treatment processes including complex ones such as anaerobic digestion. Therefore, the Anaerobic Digestion Model No. 1 (ADM1) was applied in order to evaluate the performance of a full-scale anaerobic sludge digester in this study. With the calibration of the most sensitive parameters used in the ADM1, model outputs corresponded well with the measured data obtained from the operation of the full-scale digester. The model was validated with the data acquired from the same anaerobic digester at a different operation period (360 days) and simulation results successfully predicted the digester performance. The overall results of this study demonstrated that the ADM1 can be used as a very useful tool to simulate the digestion of mixed sludge generated from full-scale wastewater treatment plants under mesophilic conditions.

Impact of salinity on the population dynamics of microorganisms in a membrane bioreactor treating produced water.

Biomass characteristics may change subject to a salinity increase when treating high strength wastewater. In this study, the impact of salinity in a membrane bioreactor (MBR) was investigated for the treatment of produced water (PW). MBR was operated as a pre-treatment prior to nanofiltration (NF) and reverse osmosis (RO). Mixed PW, that was originated from different oil, gas, and oil-gas wells, were subjected to pre-treatment for 146 days including three different operational phases: Low-salinity (~10 mS/cm), gradual increased salinity (10-40 mS/cm) and high salinity (~40 mS/cm). The results of this study showed that microorganisms could adapt using real wastewater and treat PW up to a certain level of the salinity. At high salinity levels of PW, the floc structure started to be disrupted and membrane fouling was accelerated. PCR-DGGE analysis confirmed the changes in microbial communities' composition in relation with high salinity. The results of the final treatment experiments presented that NF and RO treatment produced high-quality effluents that could be suitable for reuse.

Treatment of produced water originated from oil and gas production wells: a pilot study and cost analysis.

Produced water originated from oil and gas production wells was treated by a pilot-scale system including pre-treatment (chemical precipitation), pre-filtration, and post-filtration units. Pre-filtration unit consisted of sand filter, granulated activated carbon (GAC) filter, and ultrafiltration (UF) membrane. Post-filtration unit included reverse osmosis (RO) membrane unit. In this study, two different RO membranes including sea water (SW) and brackish water (BW) membranes were comparatively evaluated in terms of treatment and filtration performance. Besides, a cost analysis was conducted for a real scale RO membrane unit by using the data obtained from the pilot plant study. Average fluxes of 12.7 and 9.4 L/m2 h were obtained by SW and BW membrane units, respectively. Higher COD and conductivity removal efficiencies were obtained by SW membrane in comparison to BW membrane. Total cost of 0.88 €/m3 was estimated for a RO plant treating produced water with a flowrate capacity of 300 m3/d.