Wastewater Reverse Osmosis Research Articles

Impact of salinity on organic matter and nitrogen removal from a municipal wastewater RO concentrate using biologically activated carbon coupled with UV/H2O2

The concentrate streams generated from reverse osmosis (RO)-based municipal wastewater reclamation processes contain organic substances and nutrients at elevated concentrations, posing environmental and health risks on their disposal to confined receiving environments such as bays. The impact of salinity (TDS at 7, 10 and 16 g/L) of a RO concentrate (ROC) on the treatment efficiency of a biological activated carbon (BAC) system after pre-oxidation with UV/H2O2 was characterised in terms of removal of organic matter and nitrogen species, and the bacterial communities. Organic matter removal was comparable for the ROC over the tested salinity range, with 45–49% of DOC and 70–74% of UVA254 removed by the combined treatment. However, removal in total nitrogen (TN) was considerably higher for the ROC at the high salinity (TDS ∼ 16 mg/L) compared with the low (∼7 g/L) and medium salinity (∼10 g/L). Effective nitrification with high ammonium removal (>90%) was achieved at all salinity levels, whereas greater denitrification (39%) was obtained at high salinity than low (23%) and medium salinity (27%) which might suggest that the bacterial communities contributing to the greater denitrification were more halotolerant. Microbiological characterisation using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and culture based techniques showed that diversified bacterial communities were present in the BAC system as evident from different 16S rDNA. The major bacterial groups residing on the BAC media belonged to Bacillus (Firmicutes), Pseudomonas (γ-Proteobacteria), and Rhodococcus (Actinobacteria) for all salinity levels, confirming that these microbial communities could be responsible for carbon and nitrogen removal at the different salinity levels. This has implications in understanding the effectiveness and robustness of the BAC system over the salinity range of the ROC and so would be useful for optimising the treatment efficiency of the BAC system.

Impact of coagulation as a pre-treatment for UVC/H2O2-biological activated carbon treatment of a municipal wastewater reverse osmosis concentrate

After coagulation of high salinity reverse osmosis concentrate (ROC) with either alum or ferric chloride followed by UVC/H2O2 treatment, biological activated carbon (BAC) was investigated for the removal of DOC. BAC treatment mainly removed low molecular weight (LMW) neutral molecules indicating that biodegradation was the predominant mechanism of organic matter removal. Coagulation with ferric chloride gave greater DOC reductions than alum both as a stand-alone treatment and after the sequence of UVC/H2O2 and BAC treatment. However, overall reduction after the sequence of coagulation, UVC/H2O2 and BAC treatment was only marginally greater for ferric chloride (68%) than for alum (62%). Trihalomethane formation potential and N-Nitrosodimethylamine concentration decreased markedly after UVC/H2O2 treatment. UVC/H2O2 treatment of the ROC led to the generation of extreme toxicity according to the Microtox assay, but no toxicity was observed after BAC, demonstrating its advantage for enabling safe disposal of the treated ROC. Implementation of coagulation as a pre-treatment and BAC as a post-treatment markedly reduced (6–8 times) the electrical energy dose (EED) required for the UVC/H2O2 process. The sequence of coagulation, UVC/H2O2 and BAC treatment was demonstrated as a potential process for the removal of organic matter from high salinity municipal ROC.

Comparison of coagulation efficiency of aluminium and ferric-based coagulants as pre-treatment for UVC/H2O2 treatment of wastewater RO concentrate

Coagulation using two aluminium- (alum and aluminium chlorohydrate (ACH)) and two ferric-based coagulants (ferric chloride and ferric sulphate) was investigated as a pre-treatment for the UVC/H2O2 treatment of a high salinity municipal wastewater reverse osmosis concentrate (ROC). The ferric-based coagulants were generally better than alum, and ACH was the least efficient in removing dissolved organic carbon (DOC), colour, and A254 (and thus improving UV transmittance (UVT)). Ferric-based coagulants removed a greater proportion of most of the DOC fractions. However the reduction of DOC was comparable (46–49%) for alum and ferric chloride at a similar metal dosage (1mM) for UV fluence of 32×103mJ/cm2, whereas ferric sulphate performed significantly better (58%). A similar trend was observed for colour and A254 reduction, and UVT improvement. The biodegradability almost doubled for UV fluence of 32×103mJ/cm2 without pre-treatment. The change in biodegradability of the pre-treated samples during UVC/H2O2 treatment was different for each coagulant, due to the difference in the content and type of organic matter removed. Ferric chloride was superior in terms of total DOC reduction and electrical energy dose (EED) for the treatment of the high salinity ROC to meet the target residual of 15mgC/L.

Removing organic and nitrogen content from a highly saline municipal wastewater reverse osmosis concentrate by UV/H2O2–BAC treatment

Reverse osmosis (RO) concentrate (ROC) streams generated from RO-based municipal wastewater reclamation processes pose potential health and environmental risks on their disposal to confined water bodies such as bays. A UV/H2O2 advanced oxidation process followed by a biological activated carbon (BAC) treatment was evaluated at lab-scale for the removal of organic and nutrient content from a highly saline ROC (TDS 16gL−1, EC 23.5mScm−1) for its safe disposal to the receiving environment. Over the 230-day operation of the UV/H2O2–BAC process, the colour and UV absorbance (254nm) of the ROC were reduced to well below those of the influent to the reclamation process. The concentrations of DOC and total nitrogen (TN) were reduced by approximately 60% at an empty bed contact time (EBCT) of 60min. The reduction in ammonia nitrogen by the BAC remained high under all conditions tested (>90%). Further investigation confirmed that the presence of residual peroxide in the UV/H2O2 treated ROC was beneficial for DOC removal, but markedly inhibited the activities of the nitrifying bacteria (i.e., nitrite oxidising bacteria) in the BAC system and hence compromised total nitrogen removal. This work demonstrated that the BAC treatment could be acclimated to the very high salinity environment, and could be used as a robust method for the removal of organic matter and nitrogen from the pre-oxidised ROC under optimised conditions.

BAC filtration to mitigate micropollutants and EfOM content in reclamation reverse osmosis brines

The effluent organic matter (EfOM) including micropollutants present in the concentrate streams generated from reverse osmosis (RO) based municipal wastewater reclamation processes entails environmental and health risks on its disposal to the receiving environment. The suitability of a biological activated carbon (BAC) process to treat municipal wastewater RO concentrate was evaluated at lab scale during 320days of operation. BAC alone and combined UV/H2O2–BAC and ozone–BAC were performed. The combination of both advanced oxidation processes with the BAC filter improved considerably the water quality parameters. Overall eliminations for dissolved organic carbon, chemical oxygen demand and ultraviolet absorbance at 254nm ranged between 50–66%, 48–66% and 73–87%, respectively, improving considerably the removals obtained without pretreatment step (28%, 19% and 37%, respectively). Moreover, although some pharmaceuticals were partially removed by the BAC filter, the integration of the UV/H2O2 or the ozone step was necessary to achieve the total removal of those micropollutants. Finally, biomass assessment techniques allowed determining the diversity of different BAC filter scenarios.

Soil Quality of a Semi-Arid Pasture Irrigated with Reverse Osmosis Wastewater—A Case Study from Northern New Mexico

Soil quality indicators were assessed in two adjacent fields in northern New Mexico near a reverse osmosis (RO) facility. One field had been cleared of native vegetation, sowed with a pasture mix and irrigated with saline RO wastewater (electrical conductivity (EC) of 2.73 dS/m) (WW) for two years. An adjacent field of non-irrigated, undisturbed native vegetation (NV) that received only natural rainfall was sampled for comparison and assumed to be representative of baseline values. Measurements included mean weight diameter (MWD), dry aggregates > 2 mm (D > 2 mm), dry aggregates < 0.25 mm (D < 0.25 mm), wet aggregate stability, permanganate oxidizable carbon (POXC), soil organic matter, EC, pH, sand, silt and clay contents, and chemical parameters (NO3-N, P, Ca, Mg, Na, Zn, Fe, Mn and Cu). The wastewater irrigated field had more favorable soil quality indicators than the non-irrigated field, presumably due to the pasture mix and irrigation. However, the EC is higher in the WW irrigated field and will affect long-term utilization of the land for cropping, unless good soil salinity management is implemented.

Small-angle neutron scattering studies of mineralization on BSA coated citrate capped gold nanoparticles used as a model surface for membrane scaling in RO wastewater desalination.

Bovine serum albumin (BSA) coated on citrate capped gold nanoparticles (BSA-GNPs) was exposed to a simulated wastewater effluent (SSE) in order to study the mineralization and thereby mimic scaling at biofouled membranes of reverse osmosis (RO) wastewater desalination plants. RO is a leading technology of achieving freshwater quality as it has the capability of removing both dissolved inorganic salts and organic contaminants from tertiary wastewater effluents. The aim was to better understand one of the major problems facing this technology which is fouling of the membranes, mainly biofouling and scaling by calcium phosphate. The experiments were performed using the small-angle neutron scattering (SANS) technique. The nanoparticles, GNPs, stabilized by the citrate groups showed 30 Å large particles having a homogeneous distribution of gold and citrate with a gold volume fraction of the order of 1%. On the average two BSA monomers are grafted at 2.4 GNPs. The exposed BSA-GNPs to SSE solution led to immediate mineralization of stable composite particles of the order of 0.2 μm diameter and a mineral volume fraction between 50% and 80%. The volume fraction of the mineral was of the order of 10(-5), which is roughly 3 times larger but an order of magnitude smaller than the maximum possible contents of respectively calcium phosphate and calcium carbonate in the SSE solution. Considering the extreme low solubility product of calcium phosphate, we suggest total calcium phosphate and partially (5-10%) calcium carbonate formation in the presence of BSA-GNPs.

Recent Advancements in the Treatment of Municipal Wastewater Reverse Osmosis Concentrate—An Overview

Greater use of reverse osmosis (RO)-based processes in municipal wastewater reclamation presents the water industry with a major challenge regarding the sustainable management of the resultant RO concentrate (ROC) generated. This has promoted interest in investigating different approaches for the cost-effective treatment of ROC to reduce the risks associated with its disposal or reuse. This review highlights and discusses research on the treatment of ROC generated mainly from domestic wastewater.Methods employed for the treatment of municipal ROC are predominantly physicochemical processes, although biological processes with varying degrees of success in terms of the removal of organic content have also been reported. Relatively little attention has been paid to the quantification and removal of micropollutants. Due to the recalcitrant nature of some of the organics in ROC, advanced oxidation processes (AOPs) have been demonstrated to be the most effective for breaking down various pollutants and improving the biodegradability of the ROC. UV/H2O2, electrochemical oxidation, and ozonation are among the most studied AOPs for the treatment of ROC, and some have investigated posttreatment changes such as effect on molecular weight distribution and biodegradability improvement. Although these treatments appear to be promising, high energy consumption and the formation of harmful by-products during oxidative treatments are challenges that are yet to be fully addressed. Most studies have been conducted at laboratory scale and therefore large-scale investigation should be carried out to validate the effectiveness of these technologies.

Treatment of municipal wastewater reverse osmosis concentrate using UVC-LED/H2O2 with and without coagulation pre-treatment

Abstract The potential of a prototype batch reactor using ultraviolet light emitting diodes (UVC-LEDs) which emit at 255 nm in conjunction with H 2 O 2 for the treatment of a highly saline (electrical conductivity ∼22 mS/cm; DOC 32–37.5 mg/L) municipal wastewater reverse osmosis concentrate was investigated. Mineralization of organic content (measured as DOC) was low (22%) due to the low fluence rate (0.14 mW/cm 2 ), however, a large reduction in colour (94%) and A 254 (75%) occurred after delivering a UV fluence of 48 × 10 3 mJ/cm 2 at the original pH of 8.3. Fairly similar results were obtained at pH 7, but the reduction of DOC increased at lower pH with 38% and 36% achieved at pH 4 and 5, respectively. Similar trends were observed for colour and A 254 reduction. These results, in conjunction with excitation–emission matrix spectra, biological dissolved organic carbon (BDOC) assay and apparent molecular size distribution, demonstrated that the prototype system led to the breakdown of the chromophore bonds and thus changes in the molecular structure, and degradation of high molecular weight (MW) compounds to low MW compounds. Coagulation (1.5 and 3 mmol L −1 Al 3+ at pH 5) led to a significant reduction of DOC (34–38%), colour (50–66%) and A 254 (47–54%), and subsequent UVC/H 2 O 2 treatment led to further reduction in these parameters. For a target DOC reduction of 15 mg/L, the EE/O was 15 kWh/m 3 when coagulation was used as pre-treatment to the UVC/H 2 O 2 treatment (UV fluence 36 × 10 3 mJ/cm 2 ) and it reduced to less than half after biological treatment (as BDOC assay). This study demonstrated the potential of UV-LEDs as an alternative UV source for degrading the organic matter in ROC using advanced oxidation.

RO membrane cleaning using microbubbles at 6,800 m3/d wastewater RO plant in UAE

It is well known that any fouling of the membrane surface has a dramatic effect on energy consumption and plant efficiency; this is particularly true for waste water reverse osmosis (RO) plants due to the higher fouling rate. Such fouling can be very difficult to clean using commodity chemicals or even speciality chemicals. This paper explores the use of a novel cleaning process designed to increase the efficiency of membrane cleaning using microbubbles. The microbubbles were created by both a physical and chemical process, which circulate in the cleaning solution increasing turbulence at the membrane surface. These bubbles create shear forces which agitate and dislodge the foulant giving greater removal in a reduced time period. In order to demonstrate that there was no damage to the membrane surface or element using this cleaning method with microbubbles, we selected a number of 8″ membranes from the major membrane manufacturers and performed repeat cleans over a 12 month period. Membranes were autopsied to analyse presence of damage, flux and salt rejection performance, results showed that no damage was caused by using this method. These compatibility results were presented in papers at IDA Tianjin 2013. This paper explains how the multiple cleaning mechanisms (both physical and chemical) help remove foulants and restore performance at a tertiary treated sewage effluent treatment plant producing high quality water for reuse. The 6,800 m3/d plant treats conventional activated sludge with microfiltration and RO. Cleans were conducted every 2 or 3 months due to reduced flows and high differential pressures. The new cleaning method using microbubbles with specially formulated cleaning compound cleaners demonstrated that the plant could be cleaned more efficiently and in a shorter timescale than using conventional cleaners.

Photo-assisted electrochemical treatment of municipal wastewater reverse osmosis concentrate

Abstract The combination of a photochemical (UV) and electrochemical (EL) process led to enhanced degradation of dissolved organic matter in reverse osmosis (RO) concentrate produced from municipal wastewater. Treatment by UV and EL alone resulted in 25% and 35% removal of dissolved organic carbon (DOC) after 5 h, respectively. However, the hybrid process (UVEL) degraded more than 80% of DOC after the same treatment time. Fluorescence excitation–emission matrix spectroscopy and size exclusion chromatography suggest simultaneous and cooperative degradation of backbone aliphatic bonds by UV and aromatic ring cleavage by EL within the UVEL process. Overall, UVEL treatment led to efficient and non-selective degradation of dissolved organics over a wide range of molecular weights. Further, energy consumption and halogenated by-product formation (typically a limiting factor for the application of oxidation technology) were reduced in the UVEL process relative to the UV and EL processes, respectively.

Effect of coagulation on treatment of municipal wastewater reverse osmosis concentrate by UVC/H2O2

Disposal of reverse osmosis concentrate (ROC) is a growing concern due to potential health and ecological risks. Alum coagulation was investigated as pre-treatment for the UVC/H2O2 treatment of two high salinity ROC samples (ROC A and B) of comparable organic and inorganic content. Coagulation removed a greater fraction of the organic content for ROC B (29%) than ROC A (16%) which correlated well with the reductions of colour and A254. Although the total reductions after 60min UVC/H2O2 treatment with and without coagulation were comparable, large differences in the trends of reduction were observed which were attributed to the different nature of the organic content (humic-like) of the samples as indicated by the LC-OCD analyses and different initial (5% and 16%) biodegradability. Coagulation and UVC/H2O2 treatment preferentially removed humic-like compounds which resulted in low reaction rates after UVC/H2O2 treatment of the coagulated samples. The improvement in biodegradability was greater (2–3-fold) during UVC/H2O2 treatment of the pre-treated samples than without pre-treatment. The target DOC residual (≤15mg/L) was obtained after 30 and 20min irradiation of pre-treated ROC A and ROC B with downstream biological treatment, corresponding to reductions of 55% and 62%, respectively.

Assessing the potential of a UV-based AOP for treating high-salinity municipal wastewater reverse osmosis concentrate

The UVC/H(2)O(2) process was studied at laboratory scale for the treatment of one moderate (conductivity ∼8 mS/cm) and two high salinity (∼23 mS/cm) municipal wastewater reverse osmosis concentrate (ROC) samples with varying organic and inorganic characteristics. The process efficiency was characterized in terms of reduction of dissolved organic carbon (DOC), chemical oxygen demand (COD), colour and absorbance at 254 nm (A(254)), and the improvement of biodegradability. The reduction of colour and A(254) was significantly greater than for DOC and COD for all samples due to the greater breakdown of humic compounds, as confirmed by fluorescence excitation-emission matrix spectra. Fairly small differences in the reduction of DOC (26-38%) and COD (25-37%) were observed for all samples, suggesting that the salinity of the ROC did not have a significant impact on the UVC/H(2)O(2) treatment under the test conditions. The biodegradability of the treated ROC samples improved markedly (approximately 2-fold) after 60 min UVC/H(2)O(2) treatment. This study indicates the potential of UVC/H(2)O(2) treatment followed by biological processes for treating high-salinity concentrate, and the robustness of the process where the characteristics of the secondary effluent (influent to RO) and thus resultant ROC vary significantly.

Relationship between phosphate scales and silica fouling in wastewater RO membrane systems

Precipitation of calcium phosphate scale on reverse osmosis (RO) membranes continues to be a major challenge for wastewater recycling facilities. In most cases, antiscalant is dosed in combination with sulfuric acid because calcium phosphate solubility improves at lower pH. Several waste water RO plants in California that have attempted to reduce the costly acid dosing have experienced fast scale formation that has offset any savings with downtime and expensive cleaning chemicals. Online cleanings were attempted by reducing the pH to 6 for 1 week in order to reduce downtime; however, they did not fully restore flux in the tail elements and performance progressively declined over time. When these membranes were autopsied, silica was surprisingly the predominant deposit on the membrane surface, even though brine silica concentrations were only in the range of 130–160 ppm. An extensive study was conducted to simulate these conditions in a laboratory setting. Tests were conducted using various antiscalants av...

Potential of BAC combined with UVC/H2O2 for reducing organic matter from highly saline reverse osmosis concentrate produced from municipal wastewater reclamation

The organic matter present in the concentrate streams generated from reverse osmosis (RO) based municipal wastewater reclamation processes poses environmental and health risks on its disposal to the receiving environment (e.g., estuaries, bays). The potential of a biological activated carbon (BAC) process combined with pre-oxidation using a UVC/H2O2 advanced oxidation process for treating a high salinity (TDS∼10000mgL−1) municipal wastewater RO concentrate (ROC) was evaluated at lab scale during 90d of operation. The combined treatment reduced the UVA254 and colour of the ROC to below those for the influent of the RO process (i.e., biologically treated secondary effluent), and the reductions in DOC and COD were approximately 60% and 50%, respectively. UVC/H2O2 was demonstrated to be an effective means of converting the recalcitrant organic compounds in the ROC into biodegradable substances which were readily removed by the BAC process, leading to a synergistic effect of the combined treatment in degrading the organic matter. The tests using various BAC feed concentrations suggested that the biological treatment was robust and consistent for treating the high salinity ROC. Using Microtox analysis no toxicity was detected for the ROC after the combined treatment, and the trihalomethane formation potential was reduced from 3.5 to 2.8mgL−1.

Effects of operating conditions on hollow fiber membrane systems used as pretreatment for spandex wastewater reverse osmosis

Three different types of ultrafiltration (UF) membranes were investigated to treat the effluents of secondary sedimentation tank of spandex wastewater. The main parameters studied consist of the UF membrane pore size, the backwash frequency and duration time, filtration mode and the stability of the UF system. The results showed that (1) the cross-flow filtration was better in restoring K decline than the dead-end filtration; (2) the optimized backwash frequency and duration were 30 min and 2 min, respectively; (3) the modified polysulfone (PSf) UF membrane (100 kDa) was determined to be the appropriate membrane; (4) the continuous operation experiment showed that this UF system was stable.

Fouling of ultrafiltration membrane during secondary effluent filtration

Ultrafiltration (UF) membranes have been increasingly used for the pretreatment of secondary effluent in reverse osmosis wastewater reclamation plants. The fouling behavior of UF membranes during secondary effluent filtration was studied under constant pressure conditions in a cross flow filtration unit. The rate of flux decline was found to be strongly dependent on the permeate flux level, and drastic flux decline was observed at high flux during the initial period of filtration (within the first 30 min of each fouling test). Further flux decline was insignificant and a limiting flux behavior was observed. Membranes with high initial flux (>the limiting value) approached asymptotically to an identical stable flux, i.e., the limiting flux. The stable flux was strongly affected by solution chemistry (both pH and calcium concentration), with more severe membrane fouling occurred near the isoelectrical point of the foulant (pH 6) or at greater calcium concentration. Zeta potential measurements revealed that the stable flux may be correlated to the square of zeta potential of fouled membrane samples. The current study seems to suggest that foulant-foulant electrostatic repulsion plays a significant role in membrane fouling by effluent organic matter.

Oxidation of organics in retentates from reverse osmosis wastewater reuse facilities

The use of membrane processes for wastewater treatment and reuse is rapidly expanding. Organic, inorganic, and biological constituents are effectively removed by reverse osmosis (RO) membrane processes, but concentrate in membrane retentates Disposal of membrane concentrates is a growing concern. Applying advanced oxidation processes (AOPs) to RO retentate is logical because extensive treatment and energy inputs were expended to concentrate the organics, and it is cheaper to treat smaller flowstreams. AOPs (e.g., UV irradiation in the presence of titanium dioxide; UV/TiO 2) can remove a high percentage of organic matter from RO retentates. The combination of AOPs and a simple biological system (e.g., sand filter) can remove higher levels of organic matter at lower UV dosages because AOPs produce biologically degradable material (e.g., organic acids) that have low hydroxyl radical rate constants, meaning that their oxidation, rather than that of the primary organic matter in the RO retentate, dictates the required UV energy inputs. At the highest applied UV dose (10 kWh m −3), the dissolved organic carbon (DOC) in the RO retentate decreased from ∼40 to 8 mg L −1, of which approximately 6 mg L −1 were readily biologically degradable. Therefore, after combined UV treatment and biodegradation, the final DOC concentration was 2 mg L −1, representing a 91% removal. These results suggest that UV/TiO 2 plus biodegradation of RO retentates is feasible and would significantly reduce the organic pollutant loading into the environment from wastewater reuse facilities.

Fouling assessment in a municipal water reclamation reverse osmosis system as related to concentration factor

A study was conducted to assess possible formation of inorganic scaling and organic fouling in a municipal wastewater reverse osmosis (MWRO) system with microfiltration membrane treated secondary effluent as feed water. Results indicate that reject from the MWRO process can be supersaturated with sparingly soluble phosphate salts and hydroxide compounds that may form scales on the reverse osmosis (RO) membrane. The degrees of saturation, however, are much less than that in the seawater RO (SWRO) process. Therefore, a concentration factor as high as 10 can be applied to the MWRO, reflecting a recovery of 90%. Such high recovery was demonstrated using RO design software and operating a two 3-elements-in-series RO pilot plant. As the recovery rate increases, organic substances from the feed water concentrate in membrane elements at locations where flowrate is substantially reduced. At CF 5, total organic carbon and total nitrogen in the reject can be greater than 40 g/m3. The challenge of high recovery in the MWRO process then is the design and configuration of an efficient RO process in which organic and bio-fouling can be effectively controlled and advanced technologies can be integrated for fouling minimization. Key words: wastewater reclamation, reverse osmosis, membrane inorganic scaling, organic fouling, concentration factor.

Water Management In Textile Industry: Technical And Economic Aspects

Textile industry is an intensive water use sector. Consequently, enormous quantities of wastewater are generated from different manufacturing processes. Numerous opportunities for water reuse could be exploited by rational management of water use and reuse via segregation and upgrading of specific effluents using membrane filtration systems comprising ultrafiltration (UF) and reverse osmosis (RO). This paper is an endeavor to develop technoeconomic indicators for extended water reuse applications in textile industry using UF and RO. Extensive data gathered from a typical Egyptian dye house have been utilized to rationalize water use and reuse management based on different levels of pollutants in waste streams. A developed rationale enabled the identification of four applicable intervention scenarios comprising three reuse scenarios ranging from limited reuse (about 25%) to maximum reuse (about 87%) and a total end of the pipe treatment scenario. The financial assessment for a typical wastewater load (about 3500 r m/day) reveals that the maximum reuse scenario comprising UF, two stage RO in addition to direct use and low press RO is the most preferred one. Further, sensitivity analysis indicates that the annual cost of the total end of pipe treatment scenario will equal the annual cost of the maximum reuse scenario when the unit cost are US$ 0.5, 0.43 and 0.3 per cubic meter for wastewater treatment, RO and UF respectively.