Wet Well Maintenance and Cleaning Essentials

Proper Wet Well Maintenance Contributes to Sewer System Health and Decreases Risk of Sewer Backups and Associated Environmental and Economic Costs

Wet well maintenance is essential. Any number of things can cause a pump to fail resulting in sewer infrastructure damage, sewer backups or a spill into the natural environment. A recent article in Timmins Today, “Grease and Rags Clog Pumps, Raw Sewage Bypassed into Lake”, demonstrates how things can go very wrong with a sewage system and negatively impact the environment.

The need for monitoring and cleaning of pumping stations has increased over the past decade thanks to the introduction of so called “flushable wipes” and other “flushables” that increase the potential for pump plugging or failure. These items are, in fact, not flushable and whole campaigns have been set up to inform people about their damaging effects and associated costs. In addition to the increased use of “flushables”, new construction and cultural diet have contributed to the growing necessity for increased focus on wet well cleaning and maintenance.

5 Steps to Wet Well Maintenance & Cleaning

While there is no set standard when it comes to pumping station design or maintenance schedule, each station specific cleaning and maintenance needs must be assessed in accordance with the flows and sewage characteristics it receives.

There are 5 essential aspects to wet well maintenance and cleaning:

1. Wet Well Maintenance Safety Considerations

The first aspect for any maintenance and cleaning project is to ensure the project is completed in a safe manner. Wet wells are confined spaces and should be treated accordingly:

As wet wells often maintain flow during the cleaning and maintenance, extra care should be taken with gas monitoring as the gases in a wet well can change rapidly as influent is received from the sewer system.

2. Plan for Wet Well Cleaning and Maintenance

Each pump station has unique characteristics which will need to be accounted for. Some things will affect the maintenance operation, others may affect the safety procedures required. A wet well hazard assessment should be done prior to entry. Many municipalities have hazard assessments done for their pumping stations which should be reviewed with staff prior to well entry. Proper planning will tie into the safety, timing, water, and disposal aspects to ensure that the maintenance and cleanout activities are completed as efficiently and safely as possible.

 3. Timing of Wet Well Cleaning

Flows through a pumping station will vary throughout the day reflecting the hours that people inhabit those areas. In a heavy industrial area, working hours may experience higher flows, whereas a station servicing a residential area will have higher flows earlier in the morning and later in the evening.

Some pumping stations will have multiple wet wells which can be isolated thereby eliminating inflow as a concern. Smaller stations will have only one wet well and maintenance should be scheduled when flows are typically lowest. Most pumping stations have flow monitoring which will assist in determining the optimal times for wet well cleaning and maintenance.

Another timing consideration is the frequency at which stations need to be cleaned. Often a complete cleaning of a wet well is only needed 1-2 times a year. However, weekly or even daily maintenance by operators is needed to clean bar screens and readily accessible debris.

4. Water Considerations

Proper cleaning and maintenance of wet wells requires a water source to break up the debris that has built up in the pump station. Grease, plastics, hair, rags, and grit can collect in the station and require a high-pressure water source to break up, dislodge, and liquify debris for easy removal with a vacuum truck or submersible pump. If onsite water is unavailable, it can be trucked in to complete the project. 

5. Wet Well Cleaning Disposal

Once wet well clean-out debris is removed from the pumping station, it needs to go somewhere. Few wastewater treatment plants can receive the slurry/grit and debris from a pumping station wet well. Additionally, landfills will not accept material that does not pass a slump test (an indicator for overall solids concentration). Usually the material needs to be taken to a drying bed to solidify and then taken to a landfill for disposal. In some cases, it makes sense to process the material onsite, solidifying it for landfill disposal.

Implementing Procedures for Wet Well Cleaning and Maintenance Ensures Reduced Risk of Sewer Failures and Related Costs

To keep sewer systems running optimally, appropriate wet well cleaning and maintenance is crucial. Keeping the five steps to wet well maintenance in mind and ensuring that you have experienced workers performing the job will set you up for success. If you need to further explore your options for wet well maintenance, contact us; we can use our wet well maintenance expertise to customize the right plan of action for your facility.

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Aeration Tank Efficiency

Given the rising costs of energy in our province, it is important that aeration tanks that process waste water run as efficiently as possible. Whether at the municipal or industrial level, it is estimated that electricity typically accounts for about 30% of the cost in wastewater treatment. This article will examine what is needed to ensure that that you are getting the most out of your aeration tank.

Aeration System Components

Essentially aeration systems can be divided into three main parts including: airflow generation, airflow distribution and aeration control. To obtain maximum aeration tank efficiency, each of these parts must be operating at optimal levels.

Types of Blowers

As technology has improved, more efficient types of blowers have been developed. For example, systems that use straight oxygen (O2) require significantly less energy than those that use air. Furthermore, it is essential that the right size and horsepower blowers for the tank be used.

Using multiple blowers is also beneficial because it reduces the chance that a system-wide pumping failure might occur. As old air blowers fail, companies and municipalities may choose to replace them with O2 blowers. While they can be replaced all at once, doing so requires a large amount of capital so it often makes more sense financially to replace them over time to gain greater efficiency.

Process Piping

The piping system is another critical component for helping determine the efficiency of the aeration tank. If the pipes are too small, blowers with more horsepower may be required. If the pipes are too large, the system may become too difficult to control.

Equipment Components

Additionally, each of the components of the aeration tanks must meet certain standards to ensure efficiency. These components include air control valves, airflow meters and DO meters.

  • Air Control Valves – Valve size should be large enough that they can operate when they are 30-70% open. They should be installed downstream of airflow meters in order to reduce the amount of possible disturbances in the airflow.
  • Airflow Meters – There are several different types of airflow meters on the market and all work well as long as they have been properly installed. These must be placed a minimum distance either upstream or downstream of a disturbance. The manufacturer’s guidelines on this distance should be adhered to for optimal efficiency.
  • DO Meters – DO Meters have become standard in municipal wastewater plants. These optical-based meters are popular because of their reliable readings and also because they require only a minimal amount of maintenance. These meters should be placed between halfway and two-thirds down the aeration control basin.

Maintenance and Cleaning

Finally, even if you have all the best components, you won’t optimize your efficiency without proper maintenance and regular cleaning. As tanks fill up with sludge, they become less efficient but regular cleaning can help restore them.

The efficiency of an aeration tank comes down to both the components that are used as well as its ongoing maintenance. If you would like to improve the efficiency of your municipal or industrial tank, contact Wessuc today. A member of our team would be happy to meet you for a consultation and discuss possible ways to improve your efficiency.

Waste-Free Ontario

In June 2016, the Ontario Government passed the New Waste-Free Ontario Act. This new legislation hopes to create “a circular economy where we have zero waste and zero greenhouse gas emissions from the waste sector and where all resources, organic or non-organic, are used and reused productively to maximize the reintegration of recovered materials back into the economy”1

The historic linear thought of “produce-use-dispose” is harmful to the environment, financially risky, and not sustainable. Every year, approximately $1 billion worth of recoverable materials are lost to landfills across Canada.2 In 2013 alone, Ontario generated nearly 12 million tonnes of waste, which is the equivalent of almost a tonne of waste per Ontario resident each year.3

Organic waste is a particular problem because when it is landfilled it breaks down and emits methane, a greenhouse gas that is 25 times more harmful to our climate than carbon.4  If Ontario’s organic waste diversion rate is increased by 10%, we could avoid emitting nearly 275,000 tonnes of greenhouse gases.5

And yet, one particular organic waste, nutrient rich biosolids, is still being landfilled across Ontario. Each Ontario household creates approximately 1.2m3 of biosolids per year.6 And as populations across Ontario continue to increase, the amount of biosolids produced is going to continue to increase. Landfill space in Ontario is precious. There is a continuing landfill capacity deficit in Ontario, which means we have to export a significant amount of our waste to foreign landfills.7 So why are we still wasting landfill space on a material when it can be beneficially reused?

Land application of municipal biosolids is a sustainable way to not only reduce the amount of organic waste going to landfills, but also as a way to decrease greenhouse gas emissions and to provide essential micro and macro nutrients to agricultural soil across Ontario. Land application closes the circular loop outlined in the Waste-Free Ontario Act. Instead of biosolids being wasted and sent to landfill, they can be reused on agriculture fields as a very valuable source of nutrients.

  1. Ministry of the Environment and Climate Change.
  2. Natural Resources Canada, 2006.
  3. Based on data from Waste Diversion Ontario, 2013; Residential GAP Diversion Rates, and Statistics Canada, Waste Management Industry Survey 2012.
  4. Ministry of the Environment and Climate Change.
  5. Ministry of the Environment and Climate Change.
  6. Water Environment Association of Ontario.
  7. Ontario Waste Management Association, 2015