February 2009, Vol. 21, No.2

Plant Profile

Sun Peaks Utilities Treatment Facility

Location: Sun Peaks, British Columbia
Startup date: 1972
Service population: 500 to 8000,
 with expected growth to 24,000
Number of employees: 7
Average daily flow: extremely variable
Total flow, 2006: 46.44 million gal
 (175,775 m³)
Peak flow: 0.38 mgd (1438 m³/d)
Annual operating cost: $167,000

 

Sun Peaks Resort is situated at the base of Tod Mountain approximately 47 mi (76 km) northeast of Kamloops, British Columbia. Tod Mountain, with a summit elevation of 7060 ft (2152 m), originally was developed as a ski operation in the early 1960s. In 1972, the former operator decided to develop a few residential lots and formed a private utility to operate a simple community water supply and wastewater leaching field. In 1987, a simple lagoon system replaced the leaching field. While the permit granted a maximum disposal of 60,800 gal/d (230 m³/d), discharge was intermittent.

In 1992, the property was purchased, the resort’s name was changed to Sun Peaks, and a plan was designed to upgrade the ski lift and trail system and transform the area into a major four-season, destination mountain resort. The resort began evolving from a winter-only ski hill to a year-round community that eventually will support as many as 24,000 residents and visitors.

Sun Peaks’ base development has been rapidly expanding ever since. As a consequence, wastewater flows at the Sun Peaks Utilities Treatment Facility have been steadily increasing. Sun Peaks Utilities Co. Ltd. (SPUCL), which operates the Level 3 wastewater treatment plant and collection system, as well as three water treatment plants, 14 mi (23 km) of water distribution mains, and a gas storage and distribution system, has made several improvements to the lagoon system to keep pace with the increasing hydraulic and organic loading.

However, after the 1998 Christmas season, when the holding time in the 1.6-million-gal (6000-m3) lagoon dropped to fewer than 6 days, SPUCL decided to replace the lagoon with a system that could deal with the growing flows.

Upflow Sludge-Blanket Filter
After evaluating numerous alternatives, SPUCL decided to install an upflow sludge-blanket filter (USBF) system. The contract for the system was signed in July 1999, construction began the following Aug. 24, and the plant started receiving wastewater on Nov. 19, 1999. By Dec. 15 of that year, the system had stabilized, and the effluent had less than 10 mg/L biochemical oxygen demand (BOD) and 10 mg/L total suspended solids (TSS).

The design had to be flexible and allow for flows that change tenfold within a month and double on weekends. Additionally, the design had to be modular and expandable to allow for growth of the resort and the population. The modules had to be right-sized to ensure maximum operation conditions at each expansion phase, rather than building to final capacity.

The first phase installed in 1999 included two bioreactors with three sludge-blanket filters and a waste-solids storage tank. However, the resort’s growth required several upgrades and expansions to keep up with service needs. In 2001, a fourth USBF was added to the initially installed three, and in 2002, a dewatering centrifuge was installed. The dewatering centrifuge also was upgraded in 2007.

However, the flows still kept increasing, as illustrated in Table 1; consequently, a winter aeration-zone tank and an anoxic-zone tank were added in 2004, and a fifth USBF module was installed in 2008.

profiletab1thumb.jpg

Daily Flows
As illustrated in Table 1 and the figure, flows vary dramatically at the facility. The beginning of each ski season is like starting up a new plant; flows triple between the middle and end of December. Ski resorts (and this may apply to resorts in general) are not “typical” wastewater generators. Flows change dramatically from day to day and holiday period to holiday period.

profilefigurethumb.jpg

SPUCL has learned to track lift-tickets sales, snow conditions, occupancy rates, holiday periods, and overall weather trends to predict what water needs and wastewater flows to expect.

Another challenge has been coping with the resort’s fast growth. To allow for better planning of the plant expansions, Sun Peaks Resort has developed “per bed” factors to gauge both water demand and biological loading.

Influent Characteristics
To get a better reading of the incoming influent, 24-hour composite samples are collected every hour throughout the day and analyzed. The results illustrate a very uneven pattern of influent characteristics, as Table 2 shows.

profiletab2thumb.jpg

The highly variable biological loading is only one of the challenges. Sun Peaks also has a plumbing code similar to what’s in place in Australia to foster water conservation. The average water demand per person per day is currently 30.6 gal (116 L) and dropping (the Canadian average is 99 gal [375 L]). Day visitors add about 10.5 gal/d (40 L/d) per person. This leads to very high ammonia content in the influent. Additionally, the resort’s water comes from wells and has limited buffering capacity. Up to 3000 day-skiers add a lot of ammonia to the wastewater stream, resulting in reduced alkalinity during the treatment process.

To help control alkalinity, as much as 100 kg/d of slaked lime (calcium hydroxide) has been added into the anoxic and aeration compartments. During the 2006–2007 season, nearly 100 25-kg bags of lime were used.

Also, possibly due to the types of cooking oils and cleaning detergents used in the resort’s restaurants and hotels, uncommonly high chemical oxygen demand is encountered at times. Very high peak hourly flows and the fact that the influent temperature can drop as much as 5°C to 7°C within a matter of days complete the picture.

To cope with the variable biological loading, the air blowers are controlled by a continuous dissolved-oxygen monitor and variable-frequency drive system. This system ensures that the facility supplies enough dissolved oxygen without wasting energy.

Upstream management of fats, oils, and grease also has become very important, and SPUCL works with the restaurants to be proactive in dealing with their grease traps and oil-trapping systems. Items such as garbage disposals that also would add to the biological loading have been banned within the resort.

Effluent Parameters
The facility’s permitted effluent parameters are not very demanding, at 30 mg/L each for BOD and TSS. The plant delivers much better quality. BOD is typically less than 10 mg/L. TSS ranges from 5 to 20 mg/L. Ammonia is typically less than 1 mg/L. Total nitrogen varies between 10 and 20 mg/L. When the supernatant from the solids dewatering process is not returned back into the influent, the total phosphorus is biologically reduced to between 2 and 3 mg/L. However, almost all “biologically up-taken” phosphorus returns to the system when the supernatant from the new centrifuge is recycled to the equalization tank.

Effluent Disposal
Another challenge for the Sun Peaks Utilities Treatment Facility is disposing of its effluent. The current use of rapid infiltration trenches allows for a maximum daily discharge of only 225,000 gal (850 m3), and because the resort is built on the mountainside, land for additional rapid infiltration trenches is limited. Options currently under study to augment the system include stream augmentation, snow making, and golf course irrigation.