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

Abstract

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 m 3 /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.

Numerical investigation of oil droplet detachment from wall surface by a microbubble using ternary phase‐field model

“…The numerical data from Figures 2,3,5,6,9,11,14,16, and 17 are tabulated and available as a .zip file in the Supporting Information S1.…”

“…In addition, because of their hydrophobic surface, MBs easily adsorb hydrophobic substances on their surface; hence, their potential applications in cleaning processes are being considered. These include the cleaning of contaminant particles 10–12 and foulant adhered to water treatment membranes, such as microfiltration and reverse osmosis 13–16 . Unlike conventional cleaning agents, the use of MBs is a gentle and environment‐friendly method that can reduce the damage caused by traditional cleaning methods such as agent brushing, laser cleaning, and sandblasting 17 …”