This project was essentially the full replacement of the Borough of Allentown’s Wastewater Treatment Plant. The Plant has been in operation since the 1960s with original clarifiers and a trickling filter. The Plant underwent a number of minor upgrades between the 1960s and 1993. These upgrades included unit rehabilitation and the addition of various treatment processes. However, by 1995, the Plant began to fail. By 2010, nearly 50% of the Plant’s treatment units were inoperable. The only process that were operable were primary and secondary settling tanks, and chlorine disinfection.

Despite minor repairs, the deteriorated equipment, dated processes, and growing maintenance costs resulted in NJDEP violations for water quality. Specifically, the Plant could no longer adequately treat for ammonia. It was evident that extensive repairs or full replacement of the aging facilities was necessary.

Three previous designs were prepared by other engineers. Two never made it past a paper design. The third was advertised for bids. However, bids received were approximately 80% over budget and did not improve the entire treatment process. After the three prior attempts to design improvements to the Plant, the Borough authorized Roberts Engineering Group to design and administer construction of an upgrade to the Wastewater Treatment Plant. By this time, the Plant regularly exceeded discharge permit limits for effluent ammonia and was under an Administrative Consent Order (ACO) by the NJDEP which resulted in multiple costly fines.

The three (3) prior designs included partial improvements to meet NJDEP permit limits but did not address failures throughout the entire treatment system.

The improvements designed by Roberts Engineering Group included full replacement and upgrade of the treatment process, inadequate electric system, and outdated Plant control system. The new Plant was funded with a loan through the NJ Infrastructure Bank and included:

• Removal of an existing trickling filter, rotating biological contactors, and sand filters;
• Construction of an integrated fixed film activated sludge (IFAS) system;
• Installation of a grinder and automatic bar screen to remove large particles from the raw wastewater;
• Expansion of the primary and final clarifiers for greater capacity and efficiency while also elevating them above the 100-year flood elevation;
• Pulse air pumps for sludge removal;
• Upgrade of the chlorination/de-chlorination disinfection system to place it above the flood elevation and eliminate the use of chlorine gas;
• Construction of a new sludge holding tank;
• Complete upgrade to the electrical, control, and alarm systems; and
• Site improvements.

The Integrated Fixed-Film Activated Sludge (IFAS) system aided greatly in keeping the size of treatment units small. The EPA lists IFAS as an innovative emerging technology for wastewater treatment. IFAS is a biological treatment process that allows microorganisms to efficiently remove ammonia and phosphorus in solids that are removed from the effluent. IFAS is essentially a combination of two proven treatment processes. IFAS combines trickling filters that treat by a fixed-film bacteria with activated sludge suspended growth bacteria. The IFAS system at Allentown is made up of a four-compartment tank, an aeration system that provides dissolved oxygen into the water, and plastic media that are approximately 7mm in size. The plastic media act as a surface for fixed-film bacteria to grow in high volumes which allows for concentrated treatment in a smaller area. Thus, IFAS requires less space than conventional treatment systems.

As the Borough Engineer, Roberts Engineering Group designed the improvements which used IFAS as a primary component of the treatment process which has not been done before in the State of New Jersey. Typically, IFAS is added to a treatment plant to supplement existing treatment processes to meet specific effluent requirements. The use of IFAS at the Allentown Plant is for treatment to remove ammonia, total suspended solids (TSS) and biological oxygen demand (BOD) at the point of discharge. The Allentown IFAS system is the heart of the new wastewater treatment plant.

The completed WWTP has been in operation since November 2021. The IFAS treatment system has been successful in bringing the treatment process into compliance with the Borough’s NJDEP wastewater discharge permit.

Construction took approximately two years to complete and maintained continuous treatment of the Borough’s wastewater by way of phased construction. A temporary multi-phased bypass system was designed to ensure wastewater could be properly treated while construction was ongoing. The Borough Engineer, Borough Council, Contractor, and Plant Operator had to work quickly and carefully throughout the duration of the project to continue normal plant operations, solve all problems that arose, and modify the proposed improvements accordingly. State agencies were kept informed throughout construction and permit conditions were met. Despite difficulties working around the existing small site and maintaining Covid-19 precautions, construction was completed successfully. The entire project required years of planning, design, and construction by the Borough Engineer and Borough Council along with its Contractor to ensure the Allentown Wastewater Treatment Plant provides clean and safe treated water effluent.