The effectiveness of reverse osmosis (RO) membrane systems may be compromised due to fouling, of which biofouling (excessive growth of biomass) is the most troublesome. Effective control of biofouling is essential to improve membrane performance and reduce operating costs. The periodic application of chemical cleaning agents is possibly the most widely practiced method of biofouling control in RO membranes. This research investigated advanced chemical cleaning strategies for biofouling control. The first part of this study concluded that short-term accelerated biofouling studies using lab-scale membrane fouling simulators (MFSs) are a representative and suitable approach for the prediction of long-term biofouling development in membrane systems. Thereon, the superior efficiency of urea as an alternative to conventional chemical cleaning agents was demonstrated (i) at lab-scale using MFSs, (ii) for full-scale industrial spiral-wound membranes and (iii) for multiple cleaning cycles during long-term operation. Periodic chemical cleaning with urea resulted in better restoration of membrane performance, higher biomass inactivation, enhanced biofilm solubilization and removal, disintegration of extracellular polymeric substances (EPS) particularly proteins, and a considerable reduction of key biofilm-forming bacteria. This research presented enhanced chemical cleaning strategies aiming to increase the removal of biofilms, reduce biomass accumulation and its impact on membrane performance, and delay fresh biofilm formation.

Low-pressure membrane systems such as Microfiltration (MF) and Ultrafiltration (UF) have been presented as viable option to pre-treatment systems in potable water applications. UF membranes are sporadically backwashed with ultra-filtered water to remove deposited matter from the membrane and restore it. Several factors that may cause permeability and selectivity decrease are involved and numerous procedures are applicable to achieve this objective. Membrane cleaning is the most important step required to maintain the characteristics of the membrane. This research was made with the purpose of investigating the effects of acid cleaning during chemically enhanced backwashing (CEB) on the performance of ultrafiltration (UF) membranes in seawater reverse osmosis (SWRO) pretreatment. To accomplish this, the questions made were: Does the acid addition (before or after the alkali CEB) influence the overall CEB cleaning effectiveness on Dow UF membrane? Does the CEB order of alkali (NaOCl) and acid (H2SO4) affect the overall CEB cleaning effectiveness? If yes, which order is better/worse? What is the optimal acid CEB frequency that will ensure the most reliable performance of the UF?. To answer this queries, a series of sequences were carried out with different types of chemical treatments: Only NaOCl, daily NaOCl plus weekly acid, daily NaOCl plus daily acid, and weekly acid plus daily NaOCl. To investigate the consequence of acid by studying the effect of operational data like the trans-pressure membrane, resistance or permeability and support that by the analytical experiments (organic, inorganic and microbial characterization). Microorganisms were removed almost completely at hydraulic cleaning and showed no difference with addition of acid. As a conclusion of the operational data the organic and inorganic chatacterization resulted in the elimination of the first sequence due to the acummulation of fouling over time, which produces that the cleaning increases downtime, productivity diminishes, Increases water cost, shortens membrane lifespan and the frequency of cleaning in place (CIP). The elimination of the third sequence, NaOCl followed by daily acid, resulted in excessive dosing of acid which affects fibers and increases the water cost. The removal of organic carbon and inorganic fractions for the second and third sequence were investigated. The better removal of Iron was in the last sequence with value of 11.52 mg/l due to acid was dose first which target inorganic foulants. The better removal of bio polymers was obtained at the second sequence with a value of 0.95 mg/l owed to the influence of chorine CEB to acid which oxidized biopolymers with higher molecular weight to smaller, then when the acid CEB removed it in a larger amount. While the last sequence was 0.57 mg/l. It can be concluded that second sequence provided a better removal that the last sequence. To support this conclusion, the operational data was compared to the second sequence is operationally sustainable, therefore in this revision the best sequence was the second.

One of most major concerns from both cost-effective and technical point of view in membrane process industry is membrane cleaning. The aim of the project was to investigate the variations in membrane surface properties and separation efficiency of reverse osmosis membrane. Compativtive analysis have to be performed on four RO membrane before and after exposing the virgin membrane into chemical cleaning to identify and analysis the impact of the chemical cleaning on the performance of RO membrane. Commerical chemical cleaning used in this project were caustic and acidic cleaning agent. The project’s aim is the investigation of simulation software’s precision for the four membranes performance projection at different conditions of the feed water. The assessment of the membranes performance was done in the Innovation Cluster at pilot plant that was industrial in size. The main commercial elements used were the thin-film composite membranes with a spiral-wound of 8-inch polyamide. Ultrafiltration (UF) and seawater RO membrane pretreatment process was done for the red sea sourced feed water. A pressure vessel dimensioned at 8-inch was operated in conjunction with an individual element at 8 -20 m3/hr feed flow rate, with an 8 to 12 % recovery and an average 35,000-42,000 mg/L of total dissolved solids (TDS) composition for the feed water. To achieve the project’s aim in assessing the membranes, three phase experimental stages were completed. The membranes performance was assessed in terms of their water flux, salt rejection, boron rejection, bicarbonate rejection and permeate quality. In addition, the membrane surfaces were characterized after exposing the fresh membranes with a chemical cleaning reagent. The experimental results showed an increase in both permeate flow and salt passage for all studied elements. The changes in the membranes performance were systematically explained based on the changes in the charge density and chemical structure of the membranes surface. The experimental results showed that both the physical and chemical surface properties of the membranes do not significantly alter under standard industrial conditions. These results shed some light on the effects of chemical cleaning in a pilot-scale RO plant and improve our understanding to provide a potential research direction for cleaning methods of membranes.