Sewer

Town of Antigonish Sewer Treatment Plant

The Town of Antigonish is committed to keeping the public informed about our Sewage Treatment Plant (STP) and ongoing efforts to improve capacity and address odour concerns.

In early July 2026 people started noticing stronger smells coming from the lagoon. This happened around the same time as a stretch of very hot weather. The lagoon’s oxygen levels drop when water temperatures rise above 20°C. This is a threshold the plant wasn’t originally designed to exceed. Less oxygen means more odour.

The plant is also dealing with a large amount of "floatables" in the lagoon. These are non-biogradable items that are flushed that shouldn't be. They block aerators and affect the plant's efficiency.

Non-biodegradable materials floating in the lagoon.

To fight the odour, here's what our team has done and is doing:

Moving Oxygen-Rich Water to the Front: With advice from engineering consultants, we are recirculating water from the back of the lagoon to the front. This brings oxygen-rich water into the area where oxygen levels are low. In July 2026 we installed a permanent recirculation line that will ensure consistent/continuous delivery of oxygenated water to the front of the lagoon so that the good bacteria can break down waste as part of the natural treatment process.
Adding Cold Water: To help reduce temperatures and improve oxygen levels in the lagoon, we safely added cold water through the recirculation system. This approach shows positive results in reducing odour and will remain an important tool for future use.
Using Deodorizers: Two types of deodorizers have been fully automated at the plant since September 2025, further strengthening efforts to control and reduce odour.
Removing Sludge: In January 2025, we removed about two metres of sludge from Cell 1 of the lagoon—equivalent to 300 bone dry tonnes or 36 trailer loads. This helps with oxygen flow and reduces the amount of waste that bacteria have to break down, which helps cut back odour.
Cleaning Out Debris: Our team has been working hard to remove floatables and debris from the aeration system, which currently operates without a screening system. A Tender awarded in 2026 includes a screening system that will be installed by the end of Summer 2027. In the short-term, we try to vaccum these floatables off the surface of the lagoon.
Ongoing Odour Monitoring: Our team checks odour conditions daily and adjusts aeration and surface skimming as needed.

Recent Tenders

2026 Screening and Aerations Upgrades

Tender awarded to Avondale Construction. This project integrates the screening equipment, new aerators, and two new blowers to the facility.

2025 Aeration equipment upgrade

Tender awarded to Nexom. This project involves upgrading aeration equipment at our multi-cell wastewater lagoon. The new system, which includes aeration units, tubing, air distribution manifolds, and more, will enhance treatment performance and energy efficiency while integrating seamlessly with the existing facility.

2025 Awarded Screening Tender

Tender awarded to Veolia Water Technologies for a pre-purchase of screening equipment for the sewer treatment plant. This equipment will help prevent solid materials, such as wipes, pads, and other non-biodegradable items, from entering the lagoon. This will help protect the plant's equipment, reduce smells, and improve overall treatment.

Plant Upgrades Underway

We’ve partnered with CBCL Limited to make important improvements to the treatment plant. These upgrades will help us deal with odour issues and prepare the system for future growth.

The main part of this upgrade is a new screening system that will stop solid materials—like wipes, pads, and other non-biodegradable items—from entering the lagoon. This will help protect equipment, reduce smells, and improve treatment overall.

Other parts of the project include:

A new building to house screening equipment, air blowers, a lab, and office space
Extra aeration equipment at the front of the lagoon
Recirculation of cooler treated water back to the Front End or the first cell of the lagoon
A backup power system
Flow monitoring to track how much wastewater enters the plant

Timeline:

Design began: Spring 2025
Construction begins: Summer/Fall 2026
Completion target: Fall 2027

Funding:

$2.71 million from the Municipal Capital Growth Program
$3.3 million from the Town of Antigonish
$1.65 million from the Municipality of the County of Antigonish
Total project budget: $7.66 million

CBCL Limited is responsible for design, tendering, and construction oversight. The contract for their work is valued at $464,850 + HST.

What We’ve Learned from the 2024 Report

In 2024, the Town hired consultants to assess the source of odour issues. The report found:

Lagoon temperatures are now 6–7°C warmer than 20 years ago
Warmer water has reduced oxygen transfer efficiency by 15–20%
Excess sludge and buried aerators further reduce oxygen by 10–20%
Removing stormwater from the sewer system increased sewage concentration

The report is is publicly available pdf here(2.90 MB) . This report has been reviewed in accordance with Part XX (Freedom of Information and Protection of Privacy – FOIPOP) of the Municipal Government Act (MGA). The few redactions in the report, cost estimates and plant designs, have been made in accordance with sections 477 (1) and 475 (1) of Part XX of the MGA.

Capacity and Growth Planning

Our STP is permitted to treat 1.8 million gallons per day (MGD). We’re currently averaging 1.65 MGD, putting us close to capacity during rainy weather and high-usage periods.

What affects our capacity?

Inflow and Infiltration (I/I): Groundwater from leaky pipes or stormwater from roof drains and sump pumps can enter the system and use up treatment space
Non-flushables: Wipes and other items clog pipes and block aerators

On dry days, flow is about 1.46 MGD. On rainy days, it spikes. Reducing I/I lets us preserve capacity without major expansions.

How does the STP work?

We have an aerated lagoon STP that uses biological processes to consume waste and clean wastewater, before it is released back into the environment. It takes about a month for the wastewater to go through this process. This method is effective and environmentally friendly, using natural processes to treat wastewater.

Here’s how it works:

Headworks / Pre-Treatment: The first step of our STP process occurs when the sewage enters our plant. It flows by gravity through a grinder, which shreds material into pieces so they are small enough to pass through our pumps. The pumps then lift the sewage 25 feet underground up into our lagoon.

Aerated Lagoon: The next step involves using aerobic bacteria and other microorganisms (biomass) to break down the sewage in the aerated lagoon. These microorganisms feed on waste, cleaning the water naturally. This process happens in the first five (out of six) cells of the lagoon, with most of the aeration and waste breakdown focused in the first cell. In the lagoon, air is used to help the bacteria grow and do their job. There are four blowers pumping air through a pipe that runs the length of the lagoon, supplying 13 chains of aerators that are strategically placed for both mixing and aeration.

Clarification: After the biological treatment, the water moves to the final cell in the lagoon. Here, any remaining solid particles, including the biomass (dead bacteria), settle to the bottom, leaving the clarified wastewater on top to flow through three modules of three banks of sand filters.

Disinfection: To make sure the wastewater is safe to release, it is disinfected with UV light, which reduces (kills) pathogens and bacteria down to acceptable levels.

Release: Finally, the treated wastewater (effluent) is released back into nature, into the river to rejoin the water cycle. This is a standard practice regulated by the Nova Scotia Department of Environment and Climate Change.

Frequently Asked Questions

Will the plant ever be odour-free?

Let’s be clear, healthy lagoons will always have a smell; but not an offensive smell like we have had recently. Due to the nature of the plant and the business of treating sewage, there will always be a musky smell, but that smell should never leave the plant under normal operating circumstances.

Can the plant support future growth?

A statement we often see online is that the plant can’t handle the expansion we’ve seen in the fringe. With upgrades (which are coming) we do have the ability to expand what we have and support our community’s growing population.

Do we need a new plant?

Through current and planned capital investments, combined with ongoing maintenance, the Sewer Treatment Plant will meet the needs of Antigonish both now and in the future, at a lower cost to taxpayers than constructing a new treatment facility.

Why do we need to desludge more often now?

The lagoon was built to hold about 10 years of sludge. But with population growth and climate change, we now desludge based on how much sludge is present—not just time.