Nova Scotia utility uses subsurface direct discharge unit to reduce costs & improve water quality
Nova Scotia’s Halifax Regional Water Commission (HRWC), also known as Halifax Water, provides potable water, wastewater and storm water services to the Halifax Regional Municipality. Halifax Water currently manages eight watersheds as well as three groundwater sources, which collectively supply potable water to more than 86,000 customers. Water is delivered via 82,334 service connections, 31,878 of which are located within its east region. Included within the distribution system are 23 Department of Environment sampling stations.
One of the sampling stations is located in a park on Cole Harbour Road and is serviced by the Lake Major Water Supply Plant. Until 2011, water flowed regularly through a 14-in. transit line with a 2-in. connection to a car wash located prior to the dead end of the line. Toward the end of 2011, the car wash closed, resulting in a decrease in low-chlorine residuals due to non-movement in the main. Stimulating water movement required two HRWC staff to show up onsite for up to two hours, sometimes twice a week, to partially open a hydrant. This method flushed up to 50 cu m at a cost of $150 to $175 per visit. Of course, non-revenue water usage increased as well.
To help solve the water quality issue economically, HRWC’s East Water Services Superintendent Dave Hiscock directed removal of the hydrant and installation of a Mueller Hydro-Guard HG-6 automatic flushing system in its place. Subsequently, although the HG-6 resulted in far fewer man-hours at the site, water continued running down the street during flushing. Contemplation of winter climate severity issues necessitated looking into the installation of the Mueller Hydro-Guard HG-4 LongNeck subsurface direct discharge unit as the ultimate solution, as it has the capability of flushing, de-chlorinating and expelling the water into a storm sewer in an environmentally safe manner. Additionally, keeping water out of the street enhances public perception.
Installation was completed in June 2013 after an experimentation program by Halifax Water’s water quality section using a portable unit to determine optimal flush times. HRWC has reduced man-hours down to one visit per month to check the de-chlorination pucks and ensure battery strength. The Hydro-Guard HG-4’s battery has provided three years of trouble-free automatic operation. HRWC programmed its Hydro-Guard HG-4 to flush for one hour twice a day (at 10 cu m per 30 minutes). A further reduction in flush times is anticipated, since there has been no variation in chlorine residuals with the HG-4 in place. Also, little maintenance has been required since installation. The only variances of this installation are extra insulation called for by HRWC, plus the appealing rock enclosure, which helps the unit blend desirably with its park location.
Labor costs remain at $175 per flush; however, average visits to the flush site per month are down from eight to one—a savings of $1225 per month. Water use per flush immediately fell from 52 cu m to 10 cu m, which, when calculated over a two-year period, shows a decrease in non-revenue water use from 12,480 cu m to 9,000 cu m, a 3,480 cu m savings. Aggregate costs have fallen from $42,000 to $24,750 within the past two years—a total savings of $17,250 since installation.
Savings in the two years since installation of the Mueller Hydro-Guard HG-4 have been substantial, with over 51% in costs saved and over 32% less water loss. The cost of installation included the unit, labor and reinstatement. The cost of reinstatement comprised about half of the total cost; therefore, picking the optimal location is highly recommended. The investment has already been returned, and installation of more Hydro-Guard HG-4 units is being contemplated. Halifax Water’s forward-looking business plan includes a commitment to continuous improvement and ensures that the system’s technology and capacity will serve its communities into future years of growth and expansion.