Industrial Wastewater Reuse Reduces Costs and Provides Sustainable Operating Approach

Genentech Inc. is evaluating ways to reduce its city water usage and sewer disposal costs. Major water uses include the manufacturing and clean-in-place operation, cooling towers and steam boilers. Genentech undertook a study to identify and then evaluate potential opportunities. One area identified was optimizing the performance of the high purity water purification process. Another area focused on treatment and reuse of effluent from the manufacturing process. Two treatment configurations were considered. One was a biological treatment approach using a membrane bioreactor (MBR) to aerobically treat the COD in the effluent stream. The second approach used physical membrane barriers to separate the solids and organic matter from the water. An initial microfiltration (MF) step removes most of the suspended material, and a downstream reverse osmosis (RO) step removes the organic material and most of the remaining inorganic salts. The high concentration of organic material in the RO concentrate can be treated anaerobically (using the UASB technology) to recover energy in the form of methane. Capital and operating cost estimates showed that the physical membrane treatment approach was cheaper and allowed for recycling to save more city water and reduce sewer discharge flows, resulting in a payback period of about three years.