Short- and long-term fouling characteristics of reverse osmosis membrane at full scale leachate treatment plant

Abstract

This research is focused on characterizing the foulants on a reverse osmosis (RO) membrane taken from a full-scale leachate treatment plant in Thailand. The system consists of a physico-chemical pre-treatment unit and RO system and has been in operation for 2 years. Ferric chloride (FeCl(3)) was added to the open-jet sedimentation tank at 2.0-2.5 g/l dosage for chemical coagulation. The supernatant from the sedimentation tank was polished using a pressurized sand filter prior to entering the RO system. The RO unit consists of seven pressurized vessels and 42 membrane elements (6 elements in each vessel). The recovery ratio and operating pressure in the RO system were maintained at 50% and 1.5-2.5 MPa. Fouled membranes obtained from short-term (6 months) and long-term operation (2 years) were taken from the system and analyzed by autopsy and sequential cleaning methods. The analysis of foulants on the membrane surfaces revealed that Fe deposits at 3.11 g/m(2). For short-term operated membranes, water cleaning could recover 32.14 and 7.45% of initial pure water flux on the 1st and 6th membrane elements. NaOH cleaning, however, recovered more than 90% of initial flux, much higher than that of HCl solution in both elements. For long-term operated membranes, pure water flux recovery was below 5% for both 1st and 6th elements. Sequential cleaning by NaOH followed by HCl yielded the best results. Nevertheless, flux recovery through sequential cleaning of long-term operated membranes was only 35.3 and 19.1% for the 1st and the 6th elements, respectively.

Foulant characterization and distribution in spiral wound reverse osmosis membranes from different pressure vessels

“…In previous membrane autopsy studies, it was reported that the fouling layers formed on membrane surfaces were heterogeneous and significantly dependent on the flow direction of the membrane element [9,13,25]. Generally, the deposition of particles, organic, and/or colloidal contaminants is usually on the lead port of each element and the first elements in each pressure vessel.…”

“…Previous studies have demonstrated that desalination plants using brackish groundwater usually suffer from the accumulation or precipitation of inorganic salts, which mostly contain soluble multivalent ions such as calcium, aluminum, and sulfate ions [25,31]. Moreover, silica fouling also frequently occurred in groundwater desalination plants [32].…”

Reverse osmosis treatment system for landfill leachate: Operation conditions, advantages and challenges

“…Raw leachate from young landfills contains most of organic substances in biodegradable form thus can be easily treated by biological processes. For old landfills, most of the leached organic compounds are hardly or non-biodegradable forms and they should be treated by physico-chemical processes or a combination of biological and physico-chemical pro-cesses [7]. On the other hand, the use of membrane technologies allows stable quality of the permeate that can be locally reused or discharged in water bodies.…”

Membrane-free electrodeionization using strong-type resins for high purity water production

“…Besides, EDI device contains many semi-permeable ion exchange membranes, which may result in some membrane-associated problems such as concentration polarization and metal ions precipitation [10,16,17]. In our previous work, a novel membrane-free electrodeionization (MFEDI) process, combining the advantages of MBIE and EDI, was investigated and tested successfully for HPW production [18][19][20].…”