The core wastewater collection system dates back since 1969 and has been extended to serve the population of Sipayik, Pleasant Point. The collection system made up of PVC pipe, asbestos and cement pipe. The thirteen pump stations consist of Submersible pumps, and Gorman Rupp suction lift. The force main material is made up of HDPE pipe, PVC, AC pipe and DI.
The superintendent’s objective is to remove all asbestos pipe. The whole water system was made up of asbestos pipe, black iron pipe, PVC and galvanized pipe. Since 1991 the superintendent set a goal to replace the water system with Ductile Iron pipe class 52 and today 2005 he has reached his goal. The superintendent’s goal is to start working on the collection system, schedule of construction will start in FY-07.
The Passamaquoddy Tribal Wastewater Treatment Facility operates a primary and Secondary Wastewater Treatment Plant and Collection System that serves about 730 community, commercial and governmental connected users. The raw wastewater from the Pleasant Point Waste Water Treatment receives biological stabilization and pollutant removal prior to its discharge into the Passamaquoddy Bay as treated effluent.
Since the present facility started up back in the year of 1970 which was only capable of treating wastewater up to 0.040mgd.
The first up grade became operational in1994, but it had been hindered by several process problems that adversely impact its performance. These problems included the following:
– No grit removal system was included to remove sand and gravel that entered with the raw sewage. These materials accumulated in the treatment reactors and take away critical volume that is needed for the wastewater treatment. These debris must be periodically removed either mechanically with an excavator or manually by a shovel.
– The treatment plant removes pollutants by growing bacteria and microbes that feed on the organic fraction of the pollutants. The bacteria cells are then removed by settling to produce clear effluent supernatant. The proper growth of these bacteria requires that an ample supply of oxygen be available in the treatment basin. The present aeration system consisted of two rotors that were intended to aerate the reactor by churning up the water. The system is ineffective and is not able to add sufficient amounts of oxygen to keep the bacteria healthy. In addition, the rotors do not have sufficient power to properly mix the tank to keep the bacteria in suspension. As a result, the bacteria settle to the bottom of the treatment reactor and are no longer available to treat incoming wastewater. Further, the settled bacteria decompose under septic conditions that lead to the additional loss of oxygen from the overhead water.
– In order to produce clear effluent, it is imperative to grow a bacteria population that is conducive to settling at the end of the process. Good settling bacteria, called floc-formers, are readily settled after they biodegrade pollutants in the wastewater. If these bacteria are unhealthy, poorly settling bacteria, called filaments leave the plant in the effluent and contribute to poor discharge quality. The Passamaquoddy wastewater treatment plant has always struggled with filament problems due to the configuration of its treatment reactors but did produce an excellent effluent due to the experience of the superintendent.
– In order to keep all biological processes in equilibrium, excess bacteria must be periodically wasted as sludge. The ability to produce clean effluent is proportional to the plant’s ability to routinely waste excess sludge. The Passamaquoddy plant has no sludge processing facilities and only a small sludge storage reactor. This requires that sludge be wasted in liquid form frequently and trucked to the Calais wastewater treatment facility. At present 6,500 gallons per week must be removed in liquid form. This amount is expected to increase to over 20,000 gallons per week over the next twenty years. This is a costly process that is difficult to perform with the small sized staff at the plant.
The Passmaquoddy Tribal Wastewater Treatment Facility at Pleasant Point had conducted three studies over the past four years. The studies were to address the problems at the facility and plan for the improvements and up-grade to the existing facility, which consisted of the following and was completed FY-05:
– An aerated grit chamber will be added at the headworks of the plant and two primary manual grit chambers.
– A new diffused aeration system was added to the biological treatment reactor to replace the present inadequate rotor system.
– Variable Frequency Drives were installed on all motors which controls the in-put to all motor controllers.
– A selector basin was installed in cell # 1 this is for to promote growth of floc-former bacteria over poorly settling filaments.
– An 40,000 /gal aerobic sludge digester was installed to store and biodegrade excess waste sludge. The reactor will allow up to half of the organic portion of the plant’s sludge to be biodegraded and will reduce future sludge disposal volumes from 20,000 gallons per week down to only 5,200 gallons per week. This will allow sludge to be removed from the plant on a less frequent monthly basis as compared to the present twice weekly removal schedule.
-Telementary installed although out the facility and pump stations.
-The aeration basin was divided into four cells and two stages.
– 30,000 gallon surge tank installed just before the final pump station before it is pumped into the head-works.
Original Treatment Plant Design Basis:
The superintendent’s plant’s design basis after 1994 upgrade was established with the assumption that the facility would operate as an extended aeration plant with long holding times in the oxidation ditch and low hydraulic loadings on the clarifiers. The superintendent and operators have the ability to modify this method of operation and to load the facility at the borderline between extended aeration and conventional process operation. This mode of operation would allow additional loadings to be adequately treated at the plant.
The superintendent’s concept was base on prior experience with his old facility in mind. Operating a treatment plant with only the capacity of 0.040mgd and a flow of 0.090mgd on average was a challenge and a learning experience.
The acceptable design loadings to a treatment plant are based upon the sizes of the unit processes installed to treat influent wastewater. The facility’s design capacity is controlled primarily by the available reactor volume and process sizing of the plant’s oxidation ditch, final clarifiers, and chlorine contact tanks, but the superintendent proved with experience there is another theory about treatment. The present facility is capable of treating wastewater up to 150,000mgd which was based on holding the raw sewage under aeration for twenty-four hours in the oxidation ditch or reactor and maintaining a hydraulic loading rate onto the final clarifiers of 200 GHD/SF (gallons per day per square foot).
Original Upgrade Treatment Plant Design Loadings:
Parameter Original Design Value Average daily flow (GPD) 150,000 Peak hourly flow (GPD) 600,000 Organic loading (lbs/daily BOD) 300 Total suspended solids (lbs/daily TSS) 300
The plant’s design basis after 1994 upgrade was established with the assumption that the facility would be operated as an extended aeration plant with long holding times in the oxidation ditch or reactors and low hydraulic loadings on the clarifiers. But the superintendent wanted more out of the system, so with trial and error the superintendent pushed his treatment to the maximum. So in theory the superintendent had the ability to modify the method of operation and to load the facility at the borderline between extended aeration and conventional process operation. This allows additional loadings to be adequately treated at the plant as follows.
Maximum Extended Aeration Design Loadings:
Parameter Observed Value Average daily flow (GPD) 300,000 Peak hourly flow (GPD) 900,000 Organic loading (lbs/day BOD) 400 Total suspended solids (lbs/day TSS) 400
The above modified treatment loadings for the treatment plant are based upon achieving a 12 hour detention time not a 24 hour detention time in the oxidation ditch, a maximum surface overflow rate of 1200 GPD/SF in the final clarifiers, and a volumetric BOD loading rate of 20 lbs/day MCF (thousand cubic feet) in the oxidation ditch is the prime factor to achieve. This mode of operation is not highly recommended by the novice operator.
Presently to date observe the Treatment Plant Facility’s loading rates:
Parameter Observed Value Average daily flow (GPD) 90,000 Maximum monthly flow (GPD) 145,000 Maximum daily flow (GPD) 230,000 Peak hourly flow (GPD) 400,000 Average annual BOD loading 110 lbs/day Average annual TSS Loading 100 lbs/day
The above loading data and the effluent compliance records shows that the facility is not loaded up to the design capacity. Flows are slightly elevated during wet weather and high groundwater events.
The treating of wastewater at the Passamaquoddy wastewater treatment facility is taken much serious. Our primary goal is to treat a product that is suitable to drink after it leaves our facility!
The treatment plant discharges an excellent effluent quality product out into the receiving waters, on average 2 – 5 mg/L and Fecal Coliform Bacteria of <1 per 100 milliliter.
The Passamaquoddy Bay is the receiving waters, classified as SB waters, 2nd highest classification