Basic design of reverse osmosis system for treatment of high TDS refinery wastewater

ABSTRACT: Arak EmamKhomeyni refinery uses approximately 645 m3/h underground waters. To overcome water shortage, the waste water of the refinery must be treated and recycled. Preliminary studies indicate that using reverse osmosis is the proper choice. The average total dissolved solid (TDS) of the waste water in Arak refinery is approximately 1048 mg/L and varies from 400 mg/L to 2000 mg/L. For performing the task of designing suitable waste water treating plant, ROSA8 software was used. Five membrane elements (XLE-1725, HRLE-1725, XFRLE 1525/34, BW30HR-1725, and BW30XFR 1525/34) in stage one while in stage two another five membrane elements (XLE-440, HRLE-440i, XFRLE-400/34i, BW30HR-440i, and BW30XFR-400/34i) are used in this investigation. To achieve maximum recovery one pass one stage (5 design cases) and one pass two stage regimen (25 design cases) were selected and the optimum conditions performances were estimated with ROSA8 software. Results showed that utilization of a one pass flow, one stage system will lead to recover 71.4% of feed on average while two stages will lead to recover 17.42% more feed on average which is a better choice. Proper arrangement of elements is very important and affects the feed recovery. Using HRLE-1725 elements in series in first stage and BW30HR-440i in series in second stage the ROSA8 software showed that approximately 593 m3/h of waste water can be treated. The permeate quality will be 23.2 mg/L with a specific energy consumption of 0.47 kWh/m3.