Pennsylvania Department of Environmental Protection (DEP) Pilot Program Aims to Improve Drinking Water Quality by Optimizing Publicly-Owned Treatment Works’ (POTW) Discharges

By Mark Neville, PA DEP

Expanding Area Wide Optimization Program (AWOP) to include Sewage Treatment

Under terms of Pennsylvania’s Drinking Water State Revolving Fund set-asides, the Pennsylvania Department of Environmental Protection (DEP) filter plant programs section recently began a new project aimed at improving surface water quality before raw water reaches the filtration plant. This new project looks at improving the effluent water quality from publicly-owned treatment works (POTW) within five stream miles upstream of the intakes to potable water filtration plants by replicating the successful Filter Plant Performance Evaluation (FPPE) format for sewage treatment works.  The analogous evaluation, conducted out of the department’s Operations, Monitoring, and Training division at the Bureau of Water Standards and Facility Regulation, is the Wastewater Plant Performance Evaluation (WPPE).

A WPPE is a six-to-eight week on-site study performed by two DEP evaluators who are licensed sewage treatment operators, with the voluntary cooperation of a system’s official Operator-in-Charge, who continues to make operational adjustments to his plant, and the blessing of the POTW’s supervisors (boards or authorities.)  The project starts with a multi-paged performance evaluation that looks at the facility’s past operations, data, and equipment and seeks to locate “limiting factors” that affect effluent quality.  Using this evaluation as a guide, the operators then look for ways to improve the plant’s performance without incurring major capital expenditures.  Usually, the adjustments can be as simple as changing an aeration timer for a sequencing batch reactor (SBR) or by adjusting where raw wastewater is introduced to a treatment process (step feed vs. plug flow.) 

Figure 1: Instrumentation installed at WPPE site, Masontown, November 2009

The evaluators use modern instrumentation, including digital-recording ion probes purchased from HACH Corporation, to obtain continuous, on-line monitoring of plant performance throughout the duration of the site study.  In addition, for those facilities which may lack some laboratory equipment necessary for consistent process monitoring, the evaluators lend a wet-methods wastewater lab, including digital microscope, spectrophotometer, centrifuge, and portable ion meters, to the plant operators, while working to instill an ethic of consistent and regular process monitoring as a necessary precursor to making process control decisions.  This trouble-shooting and on-the-job-training aspect of the WPPE attempts to assure that plant operators will continue to pursue the goal of improved effluent water quality long after the evaluators have left the scene. 

Following on-site work, the evaluators prepare WPPE reports with reviews and recommendations tailored to each facility’s peculiar situation.

Figure 2: Laboratory Equipment staged at Lickdale, November 2009

An initial goal of the program has been to determine if non-cost-intensive operational adjustments could be used to reduce the concentration of waterborne pathogens entering downstream filter plants.  The evaluators have conducted sampling for Giardia cyst and Cryptosporidium oocyst at the outset, during, and at the completion of each evaluation.  The sampling plan includes background testing upstream of the point source, the treatment plant effluent, and the raw water entering the downstream filtration plant.  It was initially theorized that the pathogen counts would have a direct relationship to the amount of suspended solids in sewage plant effluent, and that destruction of pathogens directly correlates to turbidity in disinfection processes.

Figure 3: WPPE Evaluators Bob DiGilarmo and Marc Neville

To date, though, the evaluators have found that, without large-scale changes to disinfection technology, often incurring major capital expenditures, parasites like Cryptosporidium and Giardia are strongly resistant to destruction by conventional techniques or minor operational changes.  Therefore, one tentative conclusion drawn by the WPPE Program is that potable water filtration plant operators need to be highly attentive to these pathogens found in surface source waters.

Figure 4: Evaluator explains to Plant Operator how to interpret data from probes

 An area where substantial savings may be seen is the reduction of energy costs through effective management of treatment processes.  At one facility, where initially little control of excess dissolved oxygen concentration in the treatment process was causing high energy costs for a small municipality, evaluators were able to achieve cost savings by controlling solids levels and reducing the need for additional in-service capacity.  Use of on-line digital monitoring allowed the operator to reduce blower usage from a constant two motors to a variable both or one, creating an estimated savings of up to $8,000 per year in electricity costs.

The most “bang for the buck” has been found in nutrient reduction through process optimization.  At many of the facilities participating in the WPPE program, evaluators found that minor operational changes have helped reduce both ammonia-nitrogen and effluent nitrate concentrations, with smaller, concurrent reductions in phosphate-phosphorus.  With a large geographical area of Pennsylvania lying within the Susquehanna River drainage basin, the recent Chesapeake Bay Initiative to reduce nutrient contamination and its resultant eutrophication of valuable shellfish beds has made nutrient reduction the “holy grail” of wastewater treatment.  Many facilities are struggling with limited budgets to reduce effluent nutrients.

Figure 5, below, shows how a simple process adjustment as converting from a plug-flow, contact stabilization treatment to step-feed, extended aeration reduced toxic ammonia content in the plant’s effluent to almost nothing.

Figure 5: Reduction of ammonium ion concentration in mixed liquor, Atglen, August 2009

A second histogram, Figure 6, shows how nitrate-nitrogen was reduced at an extended aeration facility by allowing already-present microorganisms to convert nitrate to molecular nitrogen (denitrification,) thus removing nitrate from the raw water intake of the borough’s water plant downstream:

Figure 6: Reduction of nitrate ion concentration in mixed liquor, Masontown, December 2009

As the WPPE Program moves forward, the evaluators are hoping to expand the scope of the project to include any facility where assistance is needed most, working in conjunction with another department initiative that provides on-site operations assistance to sewage plant personnel. 

The ultimate aim of the WPPE Program is to improve wastewater treatment plant effluent quality through education and practice, expanding from a pilot project to an established statewide program.  Currently, evaluators located in Ebensburg and Harrisburg divide the state into two territories, with each evaluator conducting six WPPEs per year for POTWs directly influencing filtration plant intakes.  Eventually, the program may be offered to any POTW that requests the service.

For additional information, please contact Mr. Marc Neville, PA DEP Filter Plant Programs, at mneville@state.pa.us or Mr. Robert Digilarmo, PA DEP Filter Plant Programs at rdigilarmo@state.pa.us

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