DMI65 as a pretreatment to RO

DMI65 filter medium is effective in removing heavy metals in feed water and this is highly effective in protecting your expensive RO Membranes. Here is a case study that made the customer a huge savings from changing of membranes once in every 3~7 days to once in every 2 months. Interesting, right? Here is a brief

Southport Power Plant, North Carolina, installed three wells to provide an alternative water supply to address the increased costs associated with the use of city water. The well water quality required the addition of two 300 gpm reverse osmosis (RO) units as pretreatment for the ion exchange demineralizers. The original well water design, however, did not include measures to address iron in the water. The iron contained in the well water supply resulted in fouling to the cartridge filter elements and RO membranes. Early RO operation during 2004 noted lower than expected well water flow. As a result, the original two RO arrays were derated from 9:5 to 8:4 arrays with product flow reduced from 300 gpm to 250 gpm. RO operation was often performed with only one unit in service in order to lower the iron fouling rate and to increase the membrane cleaning interval. During these times, well supply from the best well flowed to the unit in service with the option to change over to the standby unit when the performance dropped off. Chemical cleanings for each RO were performed once per month with the post cleaning restoring the unit back to baseline.

Multiple CIP membrane cleanings failed to restore RO production back to baseline and as a result net RO product flow was further reduced from 250 gpm to 110 gpm. Additionally, the cartridge filter elements were fouling so rapidly that they had to be changed out at intervals that varied from once per day to once per week.?

After confirming the performance of DMI-65 with field testing the MM filter media was removed from the five multimedia filters and replaced with DMI-65 in December 2006. The DMI-65 is designed to remove iron, manganese and arsenic from the feedwater supply when operated in the presence of chlorine. Experience to date has found no further loss in RO production and the cartridge filter elements are no longer fouling at a high rate.??

The Quantum DMI-65 consists of grains of sand that have had proprietary products infused into them. This means that the active ingredients do not form a coating but become homogenous within the grains of sand. The DMI-65 acts as a catalyst in the presence of an oxidation environment created by the continuous injection of chlorine. The chlorine injection must be maintained to yield a free chlorine residual of 0.1 to 0.3 ppm at the filter effluent. The oxidation reaction causes dissolved iron, manganese and arsenic to form a solid, insoluble precipitate that is captured by the DMI-65 filter media. The captured iron is released during the filter backwash cycle.

The test filter used was a 3.5 cubic foot ion exchange vessel that was filled with Quantum DMI65 filer media to have a 24 inch bed depth and 40% freeboard for backwashing. The test vessel was prepared and operated for 24 hours to determine iron removal effectiveness and then backwashed. The post backwash return to service performance was monitored. The testing determined that the filter media was removing iron to less than 0.05 ppm and after backwashing continued to remove iron to less than 0.05 ppm. Based on the testing the recommendation was made to replace the media in the existing five filters with DMI-65 media.

Summary:

The DMI-65 filter media has performed well in removing iron contained in the well water. In addition to iron removal lowered SDI’s has addressed the fouling to down stream cartridge filter elements and RO membranes that was previously a fouling problem from filter aid chemical passage through the MM filters. Fouling associated with filter aid use resulted in cartridge filter elements fouling at a rate that the filter elements were changed from once every 1-7 days and changed with DMI-65 media to more than once per two month interval. The RO membrane fouling caused by the filter aid polymer could not be reversed with cleaning in place methods as well as a loss in performance. Based on the RO operation since DMI-65 filter media installation has filtrate iron levels are less than 0.05 ppm with no evidence of any further increase in differential pressures across the cartridge filters and the RO units. Each RO is now in the process of restoring back to baseline performance.

Do you experience a similar situation? Let's connect

Praveen Kumar, Sales Director, MEDIO, Kollam, Kerala, [email protected] M : +91 8111 975 496