In the summer of 2014, Placer County Water Agency (PCWA) in California was facing a trihalomethane (THM) crisis. Drought across the western United...
The use of MBRs in municipal wastewater treatment has grown significantly in the past few years. Wastewater treatment plants have historically required a large amount of land to construct the necessary tanks and facilities for the required levels of treatment, and MBRs provide a viable alternative to conventional treatment within a considerably reduced footprint. Additionally, there is an ever-increasing concern about pathogens, viruses, nutrients and other constituents not reduced to desirable levels by conventional treatment processes.
This membrane separation process provides a physical barrier to contain microorganisms and assures consistent high quality water. A reduced footprint and concerns for potential future regulations have allowed MBRs to move from cutting-edge technology to the treatment of choice in many situations.
MBR technology combines conventional activated sludge treatment with low-pressure membrane filtration, thus eliminating the need for a clarifier or polishing filter. It is also ideally suited for an array of municipal and industrial wastewater applications: reuse, irrigation, aquifer replenishment, wetlands development, industrial process water, boilers, cooling systems and more. Recently, MBR technology has pushed satellite treatment plants into the forefront. A satellite plant allows communities to remotely treat wastewater, thereby alleviating the need for expanding centralized sewage systems, which can be disruptive and costly.
An increasing number of recycled water facilities are designed using MBR technologies over traditional treatment methods because they offer improved water quality, smaller site requirements and reliable operation with minimal operator attendance. MBR has the ability to cost-effectively treat raw sewage for reuse; provide a reliable drought-proof supply of water that can benefit communities by reducing reliance on overstressed supplies; increase the availability of potable water; and improve the environment by decreasing discharges of wastewater to oceans, lakes, rivers, streams and creeks.
MBR systems offer a wide range of benefits. They are capable of meeting the most stringent effluent water quality standards. More importantly, the effluent quality is highly consistent with the membrane barrier and a more stable biomass.
The systems provide this high quality effluent in a greatly simplified process, requiring only headworks, biological process, membrane filtration and disinfection. In comparison, the conventional process requires additional primary treatment, secondary clarifiers, enhanced nutrient removal and media filtration prior to obtaining the same effluent characteristics.
MBR systems are simpler with fewer process components and maintenance requirements. Common maintenance is still required on mechanical parts, but operators can now avoid difficulties in operation tied to sludge settling and clarifier sludge blankets. MBR systems are easily automated and instrumented to measure performance, allowing systems to be remotely operated and monitored, which is a great benefit for satellite and small systems.
The systems are also space efficient. Commonly, MBR designs will require only 30 to 50% of the space required for conventional systems designed to meet the same treatment goals. This improved space efficiency benefits not only new facilities but allows existing facilities to increase their capacity up to three to five times without adding additional treatment volume or site footprint.
Finally, the modular nature of the membrane system allows easy phasing of facilities. Membrane modules can be delivered on a “just-in-time” basis, reducing the need for large and costly initial construction to meet long-term projections.
An evolving technology
As the demand for new water supplies and augmenting existing supplies rises worldwide, membrane technologies are increasingly utilized for providing various solutions. They continually improve, and users need to have full knowledge of the technologies’ changes, newer materials and higher efficiency systems.
Information on the latest technologies and techniques can be obtained by attending American Membrane Technology Association (AMTA) events, where industry leaders exhibit, provide technical presentations and share their global experiences.