Membranes as pretreatment to desalination in wastewater reuse: operating experience in the municipal and industrial sectors

Water shortage problems are becoming more widespread and are encouraging users to treat difficult waters and to value the reuse of wastewater. Membrane processes such as reverse osmosis (RO) have been used to treat such waters as well as sea water (SWRO). The applications, particularly for wastewater, have been limited due to the sensitivity of RO membranes to fouling and the inefficiency of the conventional pretreatment process technologies used. This paper reviews the benefits of wastewater reuse for industrial and municipal applications. It demonstrates how continuous microfiltration (CMF) pretreatment to RO can reduce capital and operating costs of RO systems, improve their efficiency and enable reliable operation on a wider variety of water sources. This information is supported by operational data from a number of CMF RO installations worldwide on difficult to treat feed waters.

The future will be dominated by unrelenting demands for increasing quantity and quality of reuse water produced at decreasing costs. The largest application has been to provide water for irrigation where pathogen-risk minimization is the primary consideration. However, the need for membrane filtration to produce a high-quality water source for either industrial use or aquifer recharge has emerged as a major application over the last 10 years. Underlying the development of non-potable water reuse is the economic value of treated water, the quality of which is driven by regulations and technology. The trend towards public private partnerships and long-term design build–operate contracts are some of the key commercial methods to achieve the challenge. Reclaimed water, as shown in this paper, can be a competitive water resource to satisfy growing, and predominantly non-potable, urban and industrial water demands. Besides generating a new water resource, and limiting effluent discharges to the environment, water reclamation and reuse conserves freshwater resources for the highest quality need, i.e., drinking water.