Leachate Treatment Facility

	Home
	Aerotech Park Services
	Community Plants
	Contact HRM Wastewater Treatment
	Eastern Passage WPCP
	Harbour Solutions
	Lakeside/Timberlea WPCP
	Leachate Treatment Facilities
	Mill Cove WPCC
	Pollution Prevention (Source Control) Program
	Technical and Underground Services
	View the Mill Cove Air Quality Study

The upgraded Leachate Treatment Facility, located at the Highway 101 Landfill Site was completed in 1988 at a cost of 4.2 million dollars. This innovative system, operated on behalf of HRM's Solid Waste Department, was the first of its kind in Canada. In 1992 further upgrades were completed on an engineered wetlands system and a lagoon system enabling a higher degree of treatment.

Leachate, a contaminated liquid which is formed by percolation of water through refuse and fill materials in a landfill site, is collected via a series of pipes placed at the bottom of a landfill site. Daily leachate flows average 35,000 gallons per day with strengths approaching 30,000 mg/L COD and 25,000 mg/L BOD.

Raw leachate from the collection system enters the pumping station wet well and is then pumped to the equalization tank.

Leachate from the equalization tank enters the pretreatment section where it is mixed with 50% sodium hydroxide solution which raises the pH to 9.5. The purpose of this process is to allow heavy metals to precipitate and to reduce dissolved solids. Settled heavy metals are removed automatically and sent to a gravity thickener. Flow from the pretreatment section enters the reactor feed wet well and is pH adjusted with hydrochloric acid before being transferred to the anaerobic reactor system.

The high rate anaerobic upflow reactors remove an average of 60-70 percent of the COD and BOD before sending the waste stream to the next stage of treatment. Each reactor employs both suspended growth and fixed film biological processes to accomplish this task. Methane produced in the reactors is used to fuel a 1,000,000 BTU boiler which in turn heats the reactors and the main treatment building.

Effluent from the reactors flows in series through two aerated lagoons which have a total volume of 17,000 cubic meters. Further removal of COD, carbonaceous BOD and ammonia nitrogen is accomplished by means of extended aeration; a process involving the breakdown of wastes by microorganisms in the presence of dissolved oxygen. Oxygen is supplied to the lagoons by means of three 2400 scfm centrifugal blowers.

Lagoon 2 incorporates an integral clarifier which allows beneficial biosolids to settle. These settled solids (activated sludge) can be recirculated back to the head of the lagoon system to provide an increase of microorganisms for further degradation of organics.Lagoon effluent flows in series through four sedimentation ponds. The purpose of these ponds is to provide sufficient residence time for solids to settle out of the waste stream. These ponds also provide facultative treatment, the breakdown of waste by microorganisms which can thrive in both aerobic and anaerobic environments.

Flow from the sedimentation ponds enters the engineered wetlands. This is a free-water surface type of wetlands system, which utilizes indigenous vegetation to remove any remaining COD, carbonaceous BOD and to provide nitrification/denitrification of the waste stream. Plants absorb nutrients and oxygen within the water by means of natural biological processes. The wetlands system is comprised of two sections, the head pond and the marsh meadow. These two sections have a total area of 5.5 hectares and are equipped with adjustable outfall gates for seasonal process optimization. The wetlands system is the first in North America to be used for leachate treatment.

The entire leachate treatment system consistently reduces COD, BOD, ammonia nitrogen and metals levels by greater than 99 percent, meeting provincial guidelines in the process.