The Town of Antigonish, Nova Scotia, operates a 1.8 MGD lagoon system consisting of one lagoon with six separate aeration zones. The lagoon is followed by a continuous upflow sand filter located in the filter building where effluent is filtered, disinfected, and then discharged. The original system of floating aeration chains with hanging diffusers was installed in 1995; after years of constant maintenance and myriad problems, the Antigonish operations department decided to look for an alternative.
About the Town of Antigonish
The Town of Antigonish’s wastewater lagoon system serves a community of approximately 5,000 residents about 100 miles northeast of Halifax, on the coast of Nova Scotia. It is home to St. Francis Xavier University and hosts the oldest continuous Highland Games outside of Scotland. The town’s average design domestic wastewater flow of 1.8 million gallons per day is treated by six-cell lagoon system and flows entirely by gravity into the plant, which simply has a grinder and no screening prior to the influent point.
After years of fixing various problems with their existing floating diffuser chains, Antigonish’s operations manager, Kyle Meisner, decided to start looking for an alternative.
Problems with Floating Aeration Chains
Antigonish’s aeration system consisted of approximately 11 floating laterals with 10 diffusers per lateral—a total of 110 diffuser racks. Each floating lateral was anchored on either end of the lagoon with stainless steel cabling, which was intended to withstand wind and keep the floating lateral straight. The lateral floated on the surface; the diffusers were suspended off the lateral and designed to swing back and forth in order to create mixing. The problems experienced at Antigonish included:
- Laterals detaching from anchors: Antigonish, being near the coast, sees a lot of wind. Wind puts stress on the laterals and often causes the cables or anchors to break. Once the lateral becomes detached, it is blown around by the wind, taking the diffusers with it. At times laterals can be blown together, causing diffusers to become tangled or detached from the lateral.
- Laterals zigzagging: The material the laterals are made of, HDPE, expands when warmed up and contracts when it gets cold. This causes the lateral to zigzag across the lagoon, moving the points of diffusion.
- Aerators breaking off the lateral: The diffuser units hang off the laterals and swing from side to side. It is very common for diffusers to break off their air lines, requiring that new diffusers be installed to replace them. From a closer look at the diffuser design, there appears to be no barb fitting on the diffuser rack to prevent the hose from pulling off.
- Unbalanced air distribution: Due to diffusers breaking off the laterals, air begins to follow the path of least resistance, blowing out of the open air lines that provide no backpressure. This creates uneven air distribution throughout the lagoon, lowering dissolved oxygen as air is not being used efficiently and eliminating mixing in some places.
“Every spring we have to spend weeks on the lagoon, fixing the aeration system,” Meisner said, “straightening the floating laterals and replacing diffusers that broke off the laterals. It’s costly to the town and my operators are sick of it.”
The Solution: Ares Aeration
Meisner evaluated the lagoon aeration alternatives and was intrigued by Triplepoint’s Ares Aeration® System. With Ares, mixing and aeration is built into one portable unit, with no moving parts. Meisner realized that this could provide the required aeration efficiency with better mixing.
Each Ares aerator sits on the bottom of the lagoon and is provided air via a self-weighted air line connected to a manifold onshore. “As soon as I saw the design I realized it was much better from a maintenance point of view than what we had: each aerator has its own continuous heavy duty air line and it was all under water—not much can go wrong.” Meisner noted, “Even if something did, I can shut the air off to that one unit from shore and all of the other units will keep working.”
The advantages of the Ares Aerator over floating aeration chains include:
- Mixing & Aeration with no moving parts: Each Ares unit utilizes fine bubble aeration for energy efficiency with a coarse bubble static tube for mixing. The airflow between each system is controlled via a static orifice; there are no moving parts on the unit. Moreover, each unit sits on the bottom of the lagoon, providing no tension to its attached air line. Ares has a very robust design that has a proven track record of success.
- Individual air lines for each aerator: Air is provided to the unit from an individual air line originating from shore. As each air line is continuous, there are no connections and, therefore, no potential failure points. In addition, the air line is heavy duty and self-sinking, which means it is not affected by wind action on the surface.
- Individual aerator control: Each air line has its own individual control valve, which allows the operator to control airflow to each unit from shore while also providing maximized redundancy; in the unlikely event one aerator has a problem, it can be shut off from shore while all the others continue operating.
- Fewer aeration units: The Ares’ oxygen transfer efficiency and mixing per unit are best in industry. Fewer aeration units are needed to accomplish the same task: instead of 110 diffusers, Antigonish only needs 43 Ares units to provide the necessary treatment. This saves on future maintenance requirements.
“We were very impressed by the Triplepoint aeration system,” Meisner noted. “It went in very easily and has been no maintenance at all. Definitely an upgrade from the floating aeration chains.” With Triplepoint’s aeration, Antigonish was able to essentially eliminate yearly maintenance on the diffuser system, improve mixing, and increase redundancy.
Learn how Ares provides superior lagoon aeration: efficient, low maintenance, and simple to install without downtime. Download the brochure.