Economical Evaluation and Operating Experiences of a Small-Scale MBR for Nonpotable Reuse

Because of their consistently high effluent quality, small footprint, and robustness to variations in influent quality, membrane bioreactors (MBRs) have become the technology of choice for small-scale reuse applications, such as in office buildings, hotels, and on cruise ships. The emergence of these systems arises from a number of drivers: lack of sewerage infrastructure, requirement for planning permission, subsidies, new guidelines for green buildings, and the public profile of recycling generally. This paper details the design and operation of a small-scale MBR providing 25 m3·d-1 of reclaimed water for toilet flushing and irrigation. Operational experience and outcomes from a 2-year evaluation period are included. An economic analysis of operational expenditures (OPEX) is also presented, revealing that for a plant of this scale, staffing costs account for the largest component (53%) of the OPEX followed by energy consumption (28%). The optimum design of these systems should therefore be focused on reducing operational complexity to minimize manual intervention.