The Middlesex County Utilities Authority (MCUA) received a $34,745,042 loan from the New Jersey Environmental Infrastructure Trust Fund to modify its existing Land-Based Residuals Management Facilities at the Edward J. Patten Water Reclamation Facility in Sayreville. The modifications are needed to improve final product quality, reduce final product quantity, reduce odor generation potential both at the plant site and in the final product, and reduce overall operating costs for processing and ultimate reuse.

The process of purifying wastewater involves the generation and removal of solid materials which are settled from raw wastewater or generated in the wastewater process. These leftover solids are referred to as biosolids, residuals, or sludge. The satisfactory treatment and disposal of residuals can be the most complex and costly operation in a wastewater system.

The MCUA will modify its current residuals handling and treatment process through a combination of new process and materials handling equipment linked by a supervisory control and data acquisition system. This system provides precise process control to obtain a consistent, uniform end-product. Modifications include a new supplemental dewatering system that reduces residuals volume prior to mixing and pasteurization, thereby reducing the quantity of alkaline materials required for stabilization. Continuous ploughshare mixers will blend the drier residuals with optimum alkaline materials, and residuals pasteurizers will provide effective monitoring and control of time and temperature to maintain a consistent output of stabilized materials. These are to be used as daily/intermediate cover at the Authority's solid waste landfill.

In developing the conceptual design, the MCUA's consultant, R3M Engineering Inc., identified the need for a low-maintenance process that will thoroughly dry the residuals to a uniform 50 - 60 percent dry solids content. Maintaining a certain amount of moisture in the dried residual benefits the subsequent downstream alkaline process while enhancing the safety of the overall system. Most drying systems typically dry residuals up to approximately 92 percent dry solids. Drying sludge to such low moisture content poses a significantly high risk of fire and explosion hazards.

Following a review of residuals drying applications in both the US and worldwide, the MCUA specified a single pass thin film sludge processor manufactured by Buss-SMS of Germany. This equipment can be installed within the spatial limitations of the existing building in a horizontal position, and all internal components can be withdrawn horizontally along integral rails for easy maintenance. In addition, the equipment can produce the homogeneous granular product necessary for the downstream processes, normally between 50 - 60 percent dry solids. This results in a very low potential for fire and explosion hazards.

In addition to installing the Sludge Processors, the construction contracts will involve the supply and installation of new product mixing and pasteurization systems as well as provide a new residuals handling system including conveyors, residuals storage bins, admixture storage and feed systems, and product loading and storage equipment. Odor control provisions will include the installation of a regenerative thermal oxidizer connected to the existing Odor Control Systems. Thermal fluid, condensate, and vapor collection systems are also included to support the thin film residuals processors.

For more information about this project, please contact Lewis Coutts, Bureau of Engineering North, at (609) 292-6894 or lewis.coutts@dep.state.nj.us by e-mail.