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City of Westfield

Posted on: May 29, 2019

Water Recovery Odor Control Scrubber Replacement Project

Figure 1 - Old Plant Equipment

Background

At the City of Westfield Water Pollution Control Plant, a dual stage wet odor control scrubber was installed in 1997 in order to eliminate noxious odors generated from the sludge dewatering room and sludge loading truckway located within the Operations Building. The odor control scrubber is designed to ventilate the processing area and treat the vented odorous air. Contaminants that cause hydrogen sulfide gas odors and ammonia odors are removed from the air prior to being discharged to the outside atmosphere. Figure 1 shows the existing unit.

Figure 1 - Old Plant EquipmentFigure 1

The 22 year old unit is currently removing noxious air from space but it is no longer able to treat it efficiently and effectively due to the normal degradation of the equipment. The existing odor control scrubber is severely corroded, outdated, and structurally degraded; it will be replaced with a new equivalent scrubber. This process is essential to prevent the collection of gases in the above mentioned spaces. Failure of this system to continue without proper operation is allowing potentially explosive and highly corrosive gases to build up during dewatering operations (which is 5 days per week), resulting in a safety and health hazard to employees, and premature corrosion damage to equipment and structures.

The Process

Wet air scrubbing is the most flexible and reliable technology for vapor-phase wastewater odor control. This technology can be used to treat virtually any water-soluble contaminant. In addition to hydrogen sulfide and "organic" odors, wet scrubbing is very effective for ammonia removal. In a wet air scrubber the odor contaminants are solubilized from the vapor phase into an aqueous chemical solution. The removal mechanism is purely chemical and is not subject to upsets as are biological processes. The chemical balance in the system is automatically and continuously maintained, even under changing loading conditions, minimizing the chance for odor break-through. The application of a multi-stage scrubber allows the utilization of a different chemical solution in each of the stages to efficiently use chemicals and target a wide range of contaminants for treatment. Figure 2 shows the new odor control scrubber to be installed.

Figure 2 - New Plant EquipmentFigure 2

New Equipment

The City of Westfield Water Pollution Control Facility has procured a contract with RH White Construction to remove and replace the existing odor control scrubber with a new Evoqua LO/PRO® system, which is a UNITARY design, two-stage, once-through, packaged Odor Control Scrubber manufactured of premium vinyl ester FRP. It consists of two counter-current stages of gas adsorption, two integral sumps, mist eliminators, exhaust fan, exhaust stack, recirculation and metering pumps, piping, valves, fittings, instrumentation and controls to make a complete and functional system. Each system is completely factory assembled and tested prior to shipment. The multi-stage design ensures a minimum of 99.0% H2S & NH3 removal. This configuration is well suited to dewatering and solids handling operations.

The existing odor control scrubber will be demolished and removed by the end of June 2019. The new equipment installation has a tentative schedule to be operational by the end of November 2019. During the five months of time between the removal and installation, the odorous air released from the process will not have a noticeable change because the current equipment to be replaced has not been treating the odorous air effectively for many years. The course of odor control treatment will continue with dosing odor oxidizing chemicals Sodium Hypochlorite and Sodium Permanganate to the sludge being processed. Once the new odor control scrubber is installed and operational, the odorous air being released from the sludge dewatering process will be treated efficiently and effectively with little to no odor being released into the atmosphere.

Jeffrey Gamelli Jr.
Deputy Superintendent Wastewater Division: DPW

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