Case Studies

Nobody offers the service we do. We work with operators to make their wastewater treatment facilities perform in ways not imagined possible. We supplement the process changes with effective engineering solutions to provide permit compliance at a fraction of the cost of traditional designs. Examples follow.

An investment in wastewater operator training and technical support is sustainably improving water quality in the State of Montana. The combined efforts and expertise of Montana regulators and municipal watewater treatment plant operators have given renewed evidence to support the position that operational optimization is an extremely potent and effective alternative to massive capital improvement projects.

One year of training and technical support demonstrated the nitrogen removal capabilities of existing wastewater treatment plants. By changing day-to-day operations at a plant not designed for biological nutrient removal, Cookeville reduced total-Nitrogen to 5 mg/L (from 20+ mg/L) and reduced total-Phosphorus to an average of 1.36 mg/L (from an average of 3.38 mg/L) while providing more sustainable treatment (no chemicals, less electricity consumed and realizing projected annual savings of $233,000.

AMHERST, MASSACHUSETTS (population 38,000) Read Full Case Study  (PDF)
BioWin modeling performed by another consultant found “there are no operational or minor modifications/retrofits that could be implemented at this facility to consistently achieve nitrogen removal.” A $61 million upgrade was recommended. Instead, staff is meeting their new limit by carefully cycling the 7.2 MGD facility’s mechanical aerators. Compliance was achieved using existing equipment, without chemicals, without increasing operating costs. Data from in-line ORP and DO probes connected to SCADA supplemented with daily aeration tank pH, alkalinity, and nitrogen series testing are used to monitor process performance. Annual Report to Massachusetts DEP (PDF).

MONTAGUE, MASSACHUSETTS (population 8,500) Read Full Case Study (PDF)
In lieu of a $4.5 million facility upgrade suggested by another consultant, we worked with plant staff to operate the 1.8 MGD facility in a sequenced aeration mode of Montague’s design. Motor-operated valves were installed on existing equipment and in-line ORP instruments were installed and connected to SCADA. The facility is Effluent nitrogen averages 5 mg/L; effluent phosphorus averages 0.85 mg/L. Operating costs have been reduced by a remarkable $100,000 per year. Newspaper article (PDF)

WESTFIELD, MASSACHUSETTS (population 42,000) Read Full Case Study (PDF)
Thousands of dollars per month in chemical savings have been realized by fermenting sludge in a storage tank. The VFA-rich sludge is pumped to the swing zone in a 6.1 MGD facility designed for nitrogen removal using the MLE process. The pre-anaerobic tank is mixed by a creative coarse bubble modification to the fine bubble diffuser system. A total-phosphorus limit of 1.0 mg/L is being met more sustainably, at far less cost, without capital investment.

Biological nitrogen removal has been achieved in this complete mix activated sludge plant. Aeration is cycled to create aerobic and anoxic conditions. Septage is stored in an empty aeration tank and is pumped into mainstream flow to provide BOD for denitrification.

UPTON, MASSACHUSETTS (population 8,000) Read Full Case Study (PDF)
The air to the first two cells of the 0.4 MGD four pass aeration system was turned off to create a low-oxygen zone for nitrate removal. Until motor operated valves are installed, the air drops are manually opened three times daily to resuspend the tank contents. The RAS pumping rate was increased to bring nitrates into the anoxic zones for improved total-N removal. Effluent total-N now averages under 6 mg/L.

PALMER, MASSACHUSETTS (population 12,000)
Nitrogen has been reduced 75% at the 4.2 MGD facility. The aeration blowers are cycled on and off to promote nitrification and denitrification. Optimization efforts are ongoing; sludge production is being reduced by raising the mixed liquor concentration and exposing the biomass to richly aerobic and strongly anoxic/fermentive conditions.

PLAINFIELD, CONNECTICUT (population 15,000)  Read Full Case Study (PDF)
A new $45 million facility was proposed by another consultant to replace Plainfield’s two 35-year old activated sludge plants. Optimization efforts demonstrated how both facilities are able to meet new nitrogen and phosphorus limits. Now, instead of replacing the plants, they are being kept in service at a savings of $40 million. Mechanical aerators are cycled at the 1.0 MGD Plainfield North to create habitats for ammonia and nitrate removal. The gravity thickener at the 0.5 MGD Plainfield Village plant ferments waste to provide the ingredients for biological phosphorus removal and optimize biological nitrogen removal.

SUFFIELD, CONNECTICUT (population 14,000) Read Full Case Study (PDF)
A much reduced internal recycle rate has made the pre-anoxic tank anaerobic sufficiently to produce volatile fatty acids (VFAs) and their uptake by phosphorus accumulating organisms (PAOs), reducing effluent total-P to 0.5 mg/L. Aeration settings in the 1.5 MGD facility’s oxidation ditches were reversed from the design settings to solubilize BOD in the first aeration zone in order to improve effluent total-N to 2.0 mg/L.

COLCHESTER-EAST HAMPTON, CONNECTICUT (population 30,000)  Read Full Case Study (PDF)
Over the course of two years, plant staff experimented with numerous process changes to improve nitrogen removal at the 3.8 MGD facility. Effluent nitrogen has been reduced by 50% and the facility operates with one aeration blower, instead of two for a $35,000 per year savings.

KEENE, NEW HAMPSHIRE (population 23,000)
To create a fermentation zone for biological phosphorus removal, Keene’s staff closed the dissolved aeration valves and turned on the mixer in an aeration tank cell. PAC is added to the flow entering the secondary clarifier to polish; a final effluent in-line ortho-P meter tracks conditions. Keene’s 6.0 MGD facility is meeting a 0.20 mg/L total-P limit in a facility not designed for phosphorus removal and saving thousands of dollars annually in chemical expenses.

COLUMBIA FALLS, MONTANA (population 5,000) Read Full Case Study (PDF)
Using existing chemical treatment equipment, Columbia Falls was struggling to maintain compliance with its 1.0 mg/L total-P limit. Anaerobic zones were established in the parallel pre-anoxic tanks to support total-phosphorus removal; chemical addition has been discontinued.

MANHATTAN, MONTANA (population 1,500)
An MLE-like biological nitrogen removal system was created by increasing the RAS (return activated sludge) rate to 2.5Q (250% of the influent flow rate). Subsequently, effluent total-nitrogen was reduced by 50%.

CONRAD, MONTANA (population 2,600)
Aeration of the modified lagoons cycles on for 2 hours and off of 1.5 hours. The air-off cycles promote nitrate-nitrogen removal; reducing the total-N to 3.5 mg/L. And, significantly reducing the electric bill.

CHINOOK, MONTANA (population 1,200)
The oxidation ditches’ mechanical aerators are cycled on and off for total-N removal. Effluent total-N dropped 50%.

We encourage you to ask any of our clients how they came to realize superior results at fantastic savings.