Municipal Sewer

The Richmond Public Works Department operates and maintains four wastewater collection and treatment systems that serve the communities of Arichat, Petit de Grat, Louisdale and Evanston. The following gives details about each of the four wastewater systems

Sewer Rates

Sewer rates are based on the prior year water consumption. See Sewer By-Law #52

Arichat

The Arichat wastewater collection system was constructed in the early 1970s as a sanitary sewage collection system only. The collection system is comprised of the following

Approximately 8 km of 200mm diameter gravity sewer;
Roughly 2 km of forcemain;
95 manholes; and
5 wastewater pumping stations.

A few extensions or additions have been made to the system since the 1970s, but the system remains for the most part the same as when initial construction was completed.

The Arichat Wastewater Treatment Plant was built in the 1970’s and is located on the shore of Arichat Harbour. A summary of the existing wastewater treatment plant is as follows

Design capacity of 454,200 L/d (120,000 USgpd).
Plant process Extended Aeration, consisting of manual screening, clarification, sludge settling tank and chlorine contact tank.
Service area includes approximately 265 single family residences, a fish processing plant, a school and a number of commercial establishments. The approximate total number of services is 388 (ADI,
1995).
Outfall extends into Arichat Harbour, exposed during low tide.

Raw wastewater flows by gravity into the concrete headworks consisting of a manually raked bar screen and grinder. The headworks effluent then flows to an extended air wastewater treatment plant. The plant is a ‘Lightnin’ treatment system as manufactured by Greey Mixing Equipment Limited in the late 1970’s. It consists primarily of the concrete aeration tank, measuring 10.1 x 20.1 x 2.4 m (485.2 m³) with aeration provided by mechanical aerators. Mixed liquor generated in the aeration tank flows to an integral rectangular secondary clarifier located adjacent the aeration tank. The clarifier is designed similar to a small packaged plant allowing gravity return of settled sludge. This sludge is referred to as return activated sludge (RAS). The concrete clarifier runs almost the entire length of the extended aeration tank (14.3 x 4.6 m). The sloped floor has a water depth ranging from 0.9 to 1.8 m. Periodically, settled sludge from the secondary clarifier must be wasted to control the mixed liquor suspended solids within the aeration tanks. This sludge, waste activated sludge (WAS), is pumped to a sludge settling tank. Clarified effluent is chlorinated and held in a chlorine contact tank prior to being released to Arichat Harbour. The sludge settling tank (2.3 x 4.6 x 2.4 m) and the chlorine contact tank (2.9 x 4.6 x 2.4 m) are located on opposite sides of the clarifier tankage. The entire plant is constructed in a concrete tank measuring 14.6 x 20.7 m.

Petit de Grat

The Petit de Grat wastewater collection system was constructed in the early 1970s. The system is comprised of the following

Approximately 2 km of 200mm diameter gravity sewer,
Roughly 1.4 km of forcemain,
32 manholes, and
4 submersible wastewater pumping stations.

The Petit de Grat wastewater plant was constructed on Petit de Grat Island in 1979. The plant remains today as it was constructed, with little in the way of modifications since its construction. It is well maintained and appears to be in good operating order.

A summary of the existing wastewater treatment plant is as follows:

Design capacity of 320 m3/d (84,000 USgpd).
Plant process Extended Aeration, consisting of manual screening,
clarification, sludge settling tank and chlorine contact tank.

Raw wastewater flows by gravity into the concrete headworks consisting of a manually raked bar screen and grinder. The headworks effluent then flows to an extended air wastewater treatment plant. he plant is a ‘Lightnin’ treatment system as manufactured by Greey Mixing Equipment Limited in 1979. It consists primarily of the concrete aeration tank, measuring 6.1 x 11.0 x 3.0 m (204 m³) with aeration provided by mechanical aerators. Mixed liquor generated in the aeration tank flows to an integral rectangular secondary clarifier located adjacent the aeration tank. The configuration of the clarifier is designed similar to a small packaged plant allowing gravity return of settled sludge. This sludge is referred to as return activated sludge (RAS). The concrete clarifier runs almost the entire length of the extended aeration tank (7.8 x 3.7 m). The sloped floor has a water depth ranging from 1.7 to 2.2 m. Periodically, settled sludge from the secondary clarifier must be wasted to control the mixed liquor suspended solids within the aeration tanks. This sludge, waste activated sludge (WAS), is pumped to a sludge settling tank. Clarified effluent is chlorinated and held in a chlorine contact tank prior to being released to Petit de Grat Harbour. The sludge settling tank (2.1 x 2.9 x 3.0 m) and the chlorine contact tank (1.2 x 2.9 x 3.0 m) are located on one side of the clarifier tankage. The entire plant is constructed in a concrete tank measuring 10.2 x 11.0m.

Louisdale

This sewage collection system services both Louisdale and portions of Lennox Passage. The serviced area is largely a residential community but has small amounts of commercial and institutional properties connected to the system. The collection system is intended to operate as a separate sanitary sewer system only. The system is comprised of 200 mm diameter gravity sewers, seven (7) Gorman Rupp duplex style self priming sewage pumping stations, one (1) Flygt submersible sewage pumping station, and associated forcemains. The system was constructed in the 1970’s, and the pumping stations were upgraded in 1996. The total length of gravity sewers is approximately 5.8 kilometres while the total length of forcemain piping amounts to roughly 2.2 kilometres. There are approximately 120 manholes within the collection system.

In 1995 Leblanc Inch Engineering Limited was retained to evaluate the existing extended air, activated sludge wastewater plant in Louisdale. At that time it was determined the existing plant was hydraulically overloaded and the proximity to several residences did not meet regulatory requirements. As a result, the Report recommended that the existing plant be replaced by a 4 cell sewage treatment lagoon constructed on the land adjacent to the entrance to Seal Cove. The lagoons were subsequently designed and constructed in the following year, including a control building housing blowers, continuous clean sand filters, and UV disinfection.

The plant services approximately 368 connections (Leblanc Inch, 1995). The lagoon was designed with a hydraulic capacity of 1,118 m³/day, equating to a 25 day retention time (HRT). Additional works included a new pump station built at the old plant site to pump wastewater across Seal Cove and enter a gravity line that feeds the new lagoons. As well, as a result of the recommendation of a detailed
receiving water study done by MaClaren Plansearch Limited, a new outfall was constructed into Lennox Passage.

The concrete headworks consists of a bar screen that is manually cleaned and a grit chamber. A 300 mm PVC pipe feeds the two unlined lagoons each measuring approximately 182 m x 60 m; the nominal water depth is 3.6 m. Each lagoon is divided by a floating baffle creating 4 cells. The control building, a split-faced concrete block structure, is 12.6 m x 11.4 m. The building contains UV disinfection equipment, a chemical mixing area & storage (alum), a lab/office, a washroom, three gravity filters and a blower room. The three filters provide effluent polishing and the surface area of each filter is 4.67 m². Lagoon aeration is provided by duplex 30 KW blowers. A 150 mm diameter ductile iron header connects to numerous aerator control chambers, controlling aeration to each of the lagoon’s four cells.

Evanston

To be updated.