The village of Harrison Hot Springs in British Columbia is known for its soothing mineral water, the sandy beaches of Harrison Lake, and scenic mountain vistas. About a mile from this “Spa of Canada” is the Harrison Hot Springs Wastewater Treatment Plant, a gem in its own right.

Keeping the waterways pristine is high priority for the plant team, and they’re doing just that. A major upgrade in 2012 added tertiary polishing with a $4 million modular membrane bioreactor (MBR) containing 128 hollow-fiber membrane modules. A UV disinfection system replaced chlorine gas for safety reasons. Final effluent is discharged to the Harrison River, which flows to the Fraser River Basin.

The final effluent quality is extraordinary, with low turbidity and non-detectable BOD and TSS. “We discharge to a fish-bearing river with salmon and sturgeon, so we’re pleased to produce such fine effluent,” says utilities lead Mark Yasinski. “Before the upgrade, we were just barely meeting our permit spec.”

While the new technology created a learning curve for the plant’s two operators, the result was well worth it: more manageable operation, better process control and troubleshooting tools. “We’ve gone from a 100,000 gpd package plant built in 1969 with no solids-handling facilities to a 793,000 gpd plant with the latest and greatest,” Yasinski says. “We’ve evolved to the 21st century.”

From old to new

The original plant consisted of a Stepaire circular steel field-erected treatment plant with an aeration tank, aerobic digester, final settling tank and chlorine contact bin. A 1980 upgrade doubled plant capacity, adding a 2.5-million-gallon equalization basin with aerators, a blower room and aeration piping. Disinfection was through 150-pound chlorine gas cylinders (Brenntag). A 2005 headworks upgrade added a grit chamber and bar screen and 7 mm Hycor Helisieve automatic fine-screen screw press (Parkson Corp.) to remove solids such as leaves, paper and cloth.

“The problem with the old plant is we had no solids-handling facilities, so we were at the mercy of the activated sludge and its settling time,” recalls Yasinski. “When solids built up, the equalization basin just got thicker.”

In 2007, the village decided to upgrade to meet growth and the possibility of stricter permit specifications. “The village was growing, and with a summer population that doubles or even triples, the system wasn’t keeping up,” says Yasinski. “The population of 1,600 expands in the summer with campsite, recreational vehicle and hotel occupants.”

The 2012 upgrade included:

• MBR with 128 hollow-fiber membrane modules (GE Power & Water)
• 2 mm rotating drum screener (IPEC)
• New diffusers for the equalization basin (Environmental Dynamics International)
• Fine-bubble aeration system (replaced coarse-bubble)
• 100 hp blowers (Aerzen)
• 420 kg/hr decanting centrifuge (Westfalia)
• UV disinfection system (Voltrex UV)

Micron-level removal

Harrison Hot Springs chose MBR technology for its ability to remove turbidity, BOD, TSS, phosphorus and ammonia nitrogen down to very low levels. “Membranes are for micron-level removal,” says Yasinski. “Our effluent turbidity is .025 NTU, our BOD is less than 5 mg/L, and TSS is less than 3 mg/L.”

The MBR is sized for 793,000 gpd maximum flow, with capability to expand to 1.5 mgd if needed. The system operates at an average flow of 363,500 gpd. System redundancy ensures uninterrupted operation if there is a problem with one of the treatment trains.

Sewage enters six transfer stations in the village and flows through force mains to the plant headworks. It then flows into the equalization basin, where fresh influent blends with activated sludge having an average MLSS of 6,000 mg/L. The mixed liquor is pumped through two submersible pumps (ABS) to the rotating drum screener.

The mixed liquor is gravity fed to the membrane tanks and filtered through the ultrafiltration modules. Two rotary lobe pumps (Boerger) permeate the clear water from the mixed liquor, which is forced into a 3,000-gallon backpulse tank. The permeate then flows into the UV station, through the outfall pipe, and to the river.

A SCADA system ties everything together: “With the old plant, we were turning all the valves by hand,” says Yasinski.

Getting up to speed

Yasinski has been with the plant for five years, and utilities technician Tyler Simmonds for four years. Simmonds is the main operator, and Yasinski assists when needed. Each holds Level 2 wastewater treatment, Level 1 water distribution, and wastewater collection certification. Simmonds is a captain with the Harrison Hot Springs Fire Department, and both he and Yasinski are paid on-call firefighters.

They ran the old plant for a year while the new plant was constructed alongside. “One of the biggest challenges in operating the old plant while the new one was being built was running the plant with not all the aerators working, and near the end, having no aerators at all,” recalls Yasinski.

“GE sent a representative to the plant for a month after the MBR system was installed, and he gave us intensive training. There were a lot of things to get used to, including learning how to balance chemicals with the bioreactor and interpreting the lab results. It took us about three months to feel totally comfortable with the system.”

GE also provided hands-on training on the MBR system’s programmable logic controller (PLC). “It has an HMI touchscreen that is pretty easy to use, since all the system parameters were pre-programmed,” says Simmonds. “But, we had to adjust some of the times and levels to make the plant run smoother.”

Voltrex UV visited to train Yasinski and Simmonds on how to maintain the UV system and bulbs. Yasinski and Simmonds also had to learn about biosolids. “I started learning about how to produce Class 2 biosolids, but it took time to get it to the right dosage,” says Simmonds. “After some trial and error, I now get it perfect every time.”

Yasinski explains, “We have a waste-activated sludge tank where we build our MLSS up to three to four times thicker than the bioreactor. We do this by pumping into the tank and letting it settle out for two or three hours. We pump more in, and the supernatant spills over until the solids return to the top, and then we stop pumping. We do this two or three times.” Next, they pump the solids to the decanting centrifuge and return the centrate to the bioreactor free of solids. They produce four metric tons of 20-percent-solids cake in eight hours. Timbro Contracting trucks the cake to its biosolids handling facility.

Easier operation

The new system has made life easier for Yasinski and Simmonds, keeping up with demand and producing water that meets permit requirements. “With the new system, if the inflow is faster than normal, we can easily balance our equalization basin,” says Simmonds. “We can process the wastewater right away and keep the equalization basin at the same level all the time.”

The SCADA system makes things easier by allowing operators to make changes after hours by logging into a remote computer. The membrane system requires some maintenance: “We clean the membranes on Monday and Friday with sodium hypochlorite by backpulsing the membrane,” says Yasinski. “This kills any bacteria. We also perform a citric acid backpulse once a week to get rid of scale.”  Every six months, they perform a recovery clean on one membrane train with higher concentrations of sodium hypochlorite and citric acid.

Yasinski and Simmonds perform their own maintenance on blowers, pumps and screens, some daily and some monthly. An automotive technician by trade, Yasinski easily taught himself how to repair the plant’s equipment. “So far, we haven’t had to repair anything on the MBR, but if there was a pump or another major part failure, we would have to fix it quickly or the equalization basin would fill up,” he says. “We would have only a few days to make the repair.”

The operators also perform lab work (samples for permit testing are sent to an off-site certified lab), clean and maintain the equipment, buildings and grounds, and conduct plant tours for the public.

As for the future, Yasinski doesn’t foresee any major changes: “The new system is working well, and the village is staying small in terms of growth. We will be removing the old plant in a few years to create more space, so maybe we’ll build a bigger maintenance building. But for now, we’re content.”