Implementation of Residuals Handling at an Immersed Membrane Treatment Facility

摘要

The Southeast Morris County Municipal Utilities Authority’s (Authority) Clyde Potts Reservoir has been serving the residents of Morristown New Jersey for over 70 years. Over that time, the treatment facilities have evolved in response to new water quality regulations. The original treatment, constructed in 1935 was limited to chloramination and pH adjustment with lime. In 1998, the Authority constructed a 0.5 MGD demonstration membrane treatment plant to evaluate this technology to comply with the requirements of the Surface Water Treatment Rule. The demonstration facility enabled the Authority to assess the effectiveness of this relatively new technology and gain valuable experience and operating data. The membranes provided for the demonstration facility were a pressurized type. Based on the operation of the demonstration plant, in 2000 the Authority commenced with the design of a full-scale 2.5 MGD membrane plant. The new plant, which uses immersed membranes, was placed into successful operation in November 2004. The residuals handling systems result in less than 1% of the feed water being discharged to waste. Each specific membrane system generates unique waste streams. The selection of the membrane system for this project was based in part on the additional systems that would be required to treat and disposed of the residuals generated by the specific membrane system. For example the membrane system that was implemented on this project did not require additional neutralization tanks as neutralization is performed within the membrane tanks. The project site is approximately 2 miles from the nearest sewer. A cost analysis was performed for construction of an express forcemain and the cost was prohibitive. Therefore all residuals needed to be either (1) recycled; (2) disposed of to a nearby stream; or (3) hauled off site. Studies were performed to assess the water quality of the membrane (waste washwater) reject and its potential impact if it were recycled to the reservoir. State regulators agreed to allow the recycle of the membrane waste washwater with monitoring provisions. A chlorinated maintenance clean of the membranes is performed on a weekly basis. This waste stream is neutralized and discharged to an on-site stream under the provisions of a NJPDES permit.Recovery cleans are performed approximately once per quarter and this waste, although neutralized, contains high concentrations of TDS and DBPs. This waste is stored on-site and hauled off-site for disposal to a wastewater treatment plant. The plant has been in full-scale operation since November 2004. Plant staff routinely monitors the quantity and quality associated with the reject and cleaning wastes, as well as the reservoir supply. This paper focuses on the evaluation, selection, and implementation of the residuals handling system.