Among various desalination methods, Reverse osmosis (RO) has emerged as the most widely adopted technology due to its efficiency and the availability of advanced polymeric membranes 1. This method not only produces potable water but is also increasingly utilized in tertiary wastewater treatment. . .

Iran is one of the arid and semi-arid countries which face with many problems in water supply. Membrane process such as Reverse osmosis (RO) is one of the advanced methods of water treatment which are widely used in arid and semi-arid areas. Reverse osmosis system produces two types of water, one purified water and the other concentrated wastewater. To reuse the concentrated wastewater in Reverse osmosis, it is necessary to remove some of the critical elements that cause problems for the membrane. In this research ZLD processes were used for removing the critical elements of Reverse osmosis wastewater of Lar city in Fars Province, Iran. The purpose of this study was to evaluate ZLD processes and determine the optimal process for recycling of Reverse osmosis wastewater. In this research different scenarios were selected for Reverse osmosis wastewater treatment including the processes of absorption, chemical precipitation and combination of these processes. Fluidized bed crystallization (calcium carbonate particles) was used for absorption process and sodium hydroxide, lime, sodium aluminate and aluminum sulfate were used for chemical precipitation processes. These chemicals were combined with wastewater in concentrations of 100, 200, 300, 400, 500 and 600 mg/L and some parameters including calcium, magnesium, chloride, sodium, potassium, pH, salinity, silica and turbidity were measured and optimum chemical concentration was determined. Optimal concentration was chosen based on maximum removal efficiency of harmful elements for Reverse osmosis membrane. Optimum removal efficiency of sodium hydroxide, lime, sodium aluminate and aluminum sulfate, were in concentration of 500, 400, 200 and 100 mg. L-1, respectively. To improve removal efficiency, the chemicals were combined together based on the optimal concentration of each chemical which was determined in the previous step. Therefore, aluminum sulfate and sodium hydroxide, aluminum sulfate and lime, sodium aluminate and sodium hydroxide and sodium aluminate and lime were mixed together. At this step the best removal efficiency was obtained in combination of optimal concentration of sodium aluminate and sodium hydroxide. Absorption process in fluidized bed crystallization was investigated for difference fluxes and optimum flux was 1. 94 m3. h-1. m-2. The maximum removal efficiency of harmful elements for Reverse osmosis membrane was observed in the combination processes of chemical deposition and absorption which occurred in fluidized bed crystallization with flux of 1. 94 m3. h-1. m-2 with adding optimized values of sodium aluminate (200 mg. L-1) and hydroxide sodium (500 mg. L-1).

Laboratory-scale Reverse osmosis (RO) studies were carried out to determine feasibility of the process for treatment of Tehran refinery oily wastewater. The effects of transmembrane pressure (TMP), cross flow velocity (CFV), temperature and pH on permeation flux and separation performance of the thin film composite (TFC) polyamide (PA, type UTC-70UB) RO membrane were investigated. At original effluent composition, high rejection of TDS (87.0%), COD (95.0%), BOD5 (95.3%), TOC (90.0%), turbidity (81.8%) and oil and grease content (86.1%) along with complete rejection of color, free oil and TSS were achieved with a reasonably high flux of 50 L/m2h. Permeation flux was found to improve with increasing TMP, CFV and temperature at constant feed concentration but rejection decreased slightly. The pH effects were found to be complex; by increasing acidic and basic nature of the feed, permeation flux was found to increase and rejection to reduce. The results showed that, RO is very suitable for treating and recycling refinery oily wastewater effluents. Also, fouling of the membrane completely followed Hermia’s model (cake filtration mechanism).

As fluoride concentration in drinking water is one of the effective parameters in human health, finding the way to remove excess amount of fluoride from drinking water is very important in water supply projects. Today, with developing in technology and finding new methods, the use of membrane technology for producing fresh water get improved. In this study the efficiency of Reverse osmosis method to remove fluoride from water was investigated. Initial concentration of fluoride, sulfate and electrical conductivity in feed water and the effect of associated cation with fluoride ion were studied. All tests adapted from “Standard Methods for Examination of Water and Wastewater”. Determination of fluoride concentration was done according the standard SPANDS method by using a spectrophotometer DR/5000. Obtain results show that with increasing in concentration of fluoride and sulfate and electrical conductivity in feed water the efficiency of RO membrane to remove fluoride reduced. In addition, this efficiency for CaF2 was higher than NaF.

Corn steep water as effluent which arrives in environment from starch processing industry has adverse effects on the environment and also large volume of fresh water is wasted. Corn step water is composed of high concentration of proteins, sugar, starch, vitamin and minerals, so it can be used as substrate for production of biological products. Hence, corn steep water concentration is important task both in environmental consideration and reuse of water. In this study, Reverse osmosis membrane was used for concentration of steep water. The pilot consisted of two parts: pretreatment and Reverse osmosis membrane. Pretreatment section contains ceramic filter with pore size of 50 micron and polypropylene filter which operates at 3-7 bar pressure. Surface area of Reverse osmosis membrane was 1.11 m2 and operating pressure is 250 psi. Results showed that permeate flux is reduced exponentially over time and transmission through the polyamide membrane of calcium ions are less than sodium and potassium ions. For membrane cleaning, at first acid solution (pH= 3.5) and then soda solution (pH= 11-11.5) were used. For removal of microorganism like bacteria from polyamide membrane, acetic acid solution (4000ppm) or hydrogen peroxide (2000ppm) could be used. In general, Reverse osmosis system with polyamide membrane is suitable process for concentration of steep water.

In the present study modeling and formulation of the thermal gradient effect on Reverse osmosis process for evaluation treated water penetration and water production are studied. Modeling is done by MATLAB using the Solution-Diffusion model. At present work, the effect of two different parameters (temperature difference gradient and salt concentration) on different parameters is studied. Studying important parameters for temperature-driven Reverse osmosis shows the direct effect of the temperature difference between the permeate-water part and the saline water part on different parameters. On temperature-driven Reverse osmosis, the temperature difference between the permeate-water part and the saline-water part acts as a driving force. The penetration rate at each salt concentration rises by increasing the temperature difference between the permeate-water part and the saline-water part. The variations of different parameters versus temperature differences for two different saline water part concentrations (1 gr/lit and 0.35 gr/lit) are presented. For 1 gr/lit salt concentration and 1.5, 2.5, and 10.8 OC temperature difference between the permeate-water part and saline-water part, treated water penetrations are obtained 0.9, 0.9545, and 1.3118 l/m2.h.bar respectively. Also, for 0.35 gr/lit salt concentration and 1.5 and 9.3 OC temperature difference between the permeate-water part and saline-water part, treated water penetrations are obtained at 0.917 and 1.167 l/m2.h.bar respectively.

Biofouling is one of the major problems in seawater membrane processes, especially in Reverse osmosis (RO) plants. Biofouling occurs as a result of the attachment and growth of microorganisms onto the membrane. Fouling increases the pressure drop across the membrane and consequently increases the energy consumption, decreases the efficiency and shortens the life time of the RO membrane. In particular, biofouling causes a decline in water flux, an increase in salt passage and an increase in biodegradation of the membrane. There is an interest to eliminate or reduce the potential of scaling and biofouling on membranes to minimize cleaning frequency. Monitoring and control of biofouling is the most difficult issue among the other types of fouling, because microorganisms and organic matters that are responsible for biofouling behave differently under different conditions. In this review article, biofilm formation and its effective parameters, conventional and novel methods of monitoring and prevention of biofouling are investigated.

The aim to achieve in this study is to recover the Cr (III) and process waters used in the wastewaters of chrome tanning operation by membrane process during leather production. In the treatment alternative contains, cartridge filter, nanofiltration (NF (NP10)), nanofiltration NF (XN45) and Reverse osmosis RO(ACM2) membranes. The raw chrome wastewater from the cartridge filter was given to NF(NP10) membranes with 3 different pressures (12bar, 16bar, 18bar). In this alternative, the most appropriate pressure is determined as 20 bar and the COD, Cr (III) and SS values were detected as, in order, 65%, 49% and 87% for the removal efficiency. 2,7 times more concentration for Cr (III) was achieved in the NF (XN45) membrane, which was used after NF(NP10) membrane and COD, SS, SO4-2, Na+ and conductivity parameters showed removal efficiencies as, 75%, 89%, 95%, 38% and 16%. The permeate from RO (ACM2) membrane was decreased to the discharge criteria’s; (Cr (III):2 mg/L, COD: 200 mg/L). As a result, the investment and the process cost of these membranes are more feasible.

Generation of electrical energy requires water as well as water conveyance and treatment to energy. For encounter to challenges and uncertainty about the water and energy nexus, requires to understand the nature of this linkage to identify, approve and execute the appropriate policies. The aim of this study is the evaluation of water and energy nexus at freshwater production by SWRO desalination. For this purpose, assuming that the electric power supplier for the desalination plant is a thermal power plant with a cooling tower or once-through-cooled, the specific water withdrawal in a thermal wet tower-and once-through-cooled plants using S-GEM model and specific energy consumption in RO plants using solution– diffusion model was calculated. The results indicate in the production energy sector, the practical power effect on fuel consumption and consequently water withdrawal. Also, in the desalination plant, the physio-chemical parameter, and temperature of feed water, and ERD type effect on specific energy consumption. Finally, the indirect volume of water withdrawal, fuel and thermal energy consumption to produce a cubic meter of desalting water was obtained which could be used by effective institutions to better manage the supply and demand of water and energy.