By Trevor Busch
Multi-million dollar upgrades to the town’s industrial wastewater lagoon and effluent irrigation systems will be required in the future to rectify serious deterioration of existing infrastructure, according to a recent engineering report.
At their Oct. 27 meeting, town council voted unanimously to accept MPE Engineering’s report on the lagoon system for information and directed administration to proceed with attempts to secure grant funding for the industrial lagoon and BNR plant sludge treatment upgrades.
Current issues include severely corroded aeration headers and branches, diffusers that have surpassed their design lifetime, a sludge blanket that makes up 40 per cent of the total aerated cell depth (solids have accumulated to a point where they have penetrated the surface of the water, contributing to odour issues), an uncommon 4160 V electrical service at the blower building which presents issues for servicing, and risk of H2S issues as the belt filter is no longer used consistently.
“We have to do something, we can’t keep it the way it is,” said Mayor Henk De Vlieger. “I think this is the first choice that we have, is we have to apply for grant funding. I think this is the most positive route to go.”
Industrial wastewater from the town’s industrial collection system is conveyed to the lagoon system. The original aerated lagoon was commissioned in 1988 to treat industrial wastewater, and featured three 400 hp centrifugal blowers, two electric motors, and one diesel engine. Wastewater flows through three aerated treatment cells and into the upper storage cell, and pumped overland to the lower storage cell. Treated effluent is drawn into the irrigation pump station where it is pumped to neighbouring farmland for disposal.
From 2000 to 2009 the aerated lagoon treated both industrial and municipal wastewater (the new BNR Wastewater Treatment Plant was commissioned in 2009 to treat municipal wastewater).
Under the existing system at the BNR Wastewater Treatment Plant, waste activated sludge from BNR is thickened and pumped into sludge holding tanks. Fermented sludge as well as scum from the BNR primary and secondary clarifiers is also sent to the sludge holding tanks. From the the holding tank the sludge is pumped to a belt filter press, which de-hydrates the sludge to approximately 20 per cent solids, which are then trucked to a disposal site (landfill or composting facility). Supernatant (liquid lying above a solid residue) from the belt filter press is sent back to the wastewater treatment plant headworks or to the industrial lagoon. Existing sludge holding tanks have a five-day holding capacity.
The current capacity of the town’s industrial wastewater lagoon system is expected to meet or exceed requirements for the immediate future, but is in need of significant upgrades.
“We looked at the capacity of your lagoon system,” said MPE project manager Andrew Kleisinger. “It meets the needs of your current demand. Your current demand on your industrial lagoon is not really expected to change much. Your industrial wastewater stream is a fairly consistent volume. The capacity that you have in terms of lagoon size is more than sufficient.” “Industrial wastewater is about 50 per cent of the municipal wastewater volume. Capacity is not an issue at all.”
Three alternatives were presented to council for their consideration in the report. The first proposes upgrades to the aerated lagoon system, including replacement of current blowers with four 175 hp positive displacement blowers, header piping replacement, diffuser piping replacement, electrical service change (4160 V to 600 V service), 900 kW diesel powered back-up power generator, and a permanent control structure to divert flow by gravity from Cell 5 to the lower storage cell.
Under this alternative, BNR Wastewater Treatment Plant sludge would continue to be pumped to the lagoon system, but would be enhanced with the inclusion of a new lift station at the BNR Plant to pump sludge stream to the industrial lagoon. The estimated cost for this alternative is $5.9 million.
The second alternative — ultimately the alternative recommended by MPE Engineering for implementation by the town — would see identical upgrades to the lagoon system with the exception of only three 150 hp positive displacement blowers and a 450 kW diesel powered back-up generator) but would see more extensive upgrades to the BNR Wastewater Treatment Plant to more effectively handle sludge treatment. This would include decommissioning and removal of the existing belt filter press, upgrading mixing operations in the sludge holding tanks, installation of a centrifuge and associated piping, and upgraded ventilation equipment in the centrifuge room. The estimated cost for this alternative is $4,780,000.
“We’d like to proceed to grant funding on this project based on council’s recommendation,” said public works manager Gary Scherer.
The third alternative would be a complete upgrade of the BNR Wasterwater Treatment Plant to treat industrial wastewater from the town’s industrial customers to accept additional loading, as well as upgrades to the town’s collection system to direct all industrial flow to the plant. The estimated cost for this alternative is $15-20 million.
“We’re very fortunate to have the system that we have, and we’re fortunate that we have a place that we can put it on some lands that people can use,” said Coun. Randy Sparks. “The nature of what happens out there, there’s going to be failures in piping and things like this just because of what it handles on a daily basis. The blower system needs to be addressed. It’s far too costly to the the Town of Taber toward energy alone. I think it would be very wise of this council to move ahead with grant funding. Let’s get it in place and get this dealt with, and move on.”
As assessment of the effluent irrigation system was also conducted, with findings showing the building is in useable condition, however piping is showing excessive corrosion and the layout is inefficient which could improperly load pumps. The report determined the electrical equipment is past its useful life and the end suction pump needs replacement, but other pumps appear to be in good condition.
Recommended upgrades for the effluent irrigation system include full replacement of pumps, piping, valving and instrumentation, HVAC system replacement, a control system setup, replacement of underground piping from pump station to irrigation lands, and replacement of irrigation pivot equipment (five quarter sections are currently under irrigation). The estimated cost for these upgrades is $3,520,000.