Town of Port Hawkesbury

Wastewater Treatment

The Town of Port Hawkesbury's wastewater system consists of one old trickling filter wastewater treatment plant (WWTP), one new WWTP and seven lift stations (LS).

The Old Wastewater Treatment Plant

The old WWTP is a 30 yr old trickling filter plant, The plant was one of the first such plants in North America. The plant has been in service for a very long period and is coming to the end of its service life. The plant consists of two trickling filter towers, sedimentation basins, main building, digester and chlorine contact chamber. The plant is scheduled to be decommissioned within a six month period of the new WWTP being commissioned.

The New Wastewater Treatment Plant

The Town of Port Hawkesbury is currently constructing a new WWTP. The WWTP is a "Sequencing Batch Reactor" (SBR) technology; the plant is being constructed in partnership with the County of Inverness and funded through the Canadian Infrastructure Program. The plant will receive wastewater from both Port Hawkesbury and Port Hastings wastewater systems. The plant is located on North Reeves Street between the Town of Port Hawkesbury and Port Hastings.
The plant is designed to treat a maximum flow rate of 3,000,000 gallons a day of wastewater. With the construction of additional SBR tanks the plant can be expanded to handle any additional future flows. The plant is designed to reduce the wastewater to less then 20 mg/l of Biological Oxygen Demand (BOD) and less then 20 mg/l Suspended Solids (SS). The plant will also receive leachate from the new landfill in Guysborough County. The plant is also set up to receive loads from septic trucks. The activated sludge SBR process performs the same treatment steps as a conventional activated sludge process. Both systems accomplish aeration, sedimentation and clarification. The difference between the two systems is that in conventional plants the process is a continuous flow process, all of the treatment steps are carried out at the same time in individual tanks. The SBR process of activated sludge treatment is accomplished in a single tank through sequencing stages. This eliminates the need for additional tanks for sedimentation and clarification, and does not require the conventional return sludge handling facilities. The sequencing series for treatment consists of the following process stages: FILL, REACT (aeration), SETTLE, DECANT (withdrawal of clarified effluent) and IDLE,

This complete cycle generally occurs two to six times a day in each SBR tank:. The new WWTP will have four SBR tanks. Wastewater will enter the process first by being pumped through an aerated grit chamber and channel grinder:: The aerated grit chamber will remove most of the heavier grit particles, while keeping the lighter organic particles in suspension:: A grit hopper will be located at the bottom of the chamber for the accumulation of grit, which can be removed on a periodic basis,. The grinder will be located at the exit of the grit chamber and will macerate any incoming objects, not removed in the grit chamber, to a size small enough to prevent damage to any downstream pumps or other mechanical equipment. Following the grinder the wastewater will drop into the equalization tank (EQ}.: The EQ tank will store the flow, which will be delivered to the SBR's in batches and will be sized to provide storage of excess flow at the peak hourly flow rates. The wastewater will enter one of four concrete SBR tanks from the EQ tank. The wastewater will be transferred to the SBR tanks with feed pumps. The SBR tank is where the treatment of the wastewater takes place: Following treatment in the SBR tanks the wastewater is allowed to settle and the clear top portion of the tanks are decanted off. The decanted liquid is sent through a disinfection unit (ultraviolet light) and out through the outfall pipe to the Strait of Canso by gravity.

Over time there is an accumulation of excess solids buildup in the SBR tanks:, These solids will be pumped daily from the SBR tanks to one of three aerobic digesters via submersible pumps located at the bottom of each SBR tank, The digesters will perform a two stage process, reduction of volatile solids and thickening of the solids:: The thickened sludge will then be pumped on to a centrifuge:. The centrifuge will dewater the sludge. The dewatered sludge will then be hauled by truckload to the Guysborough landfill.

Lift Stations

Lift stations are pumping stations that pump the wastewater from low lying areas to an elevation where the wastewater can either flow by gravity to the WWTP or to another lift station that will pump it to the VWVTP. The Town of Port Hawkesbury currently has seven lift stations throughout its wastewater collection system. Two of the existing lift stations (LS) in Port Hawkesbury will require modification and/or upgrades in order to pump the Town's wastewater to the new WWTP: The stations will be designed to handle current peak flow rates as well as the estimated future flow rates for the next 25 years.

The new WWTP has been in commission since April 2007.