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Septic tanks are designed to treat and manage wastewater from homes and businesses that aren’t connected to a main sewage system. Septic Tanks have three compartments. Here’s how they work together:

1. Separation of Solids: Wastewater enters the first chamber of the septic tank, where solids settle at the bottom. Heavier materials form ‘sludge’, while a small amount of anaerobic breakdown starts to occur. This process helps separate solid waste from liquid without the presence of oxygen.
2. Scum Layer & Liquid Flow: The liquid then flows into the second chamber, passing through a baffle that keeps solids behind. A ‘scum layer’ forms on top, trapping odours and preventing them from escaping. A specially designed dip outlet pipe ensures that only the liquid passes through to the next stage, preventing blockages caused by scum.
3. Percolation: In the final stage, the liquid flows into a percolation area, where it undergoes further treatment by filtering through the soil. This process helps remove harmful bacteria and nutrients before the wastewater re-enters the groundwater.

By efficiently managing solids, liquids, and percolation, septic tanks provide an effective and eco-friendly solution for wastewater treatment in off-main systems​.

We design and build all Commercial Sewage Treatment plants in house. ​​The exclusive provider of Tricel Maxus Combi in NI/ROI, this is built using advanced SAF technology (Submerged Aerated Filter) to treat wastewater through a four-stage process in a single tank. It is available in two models: gravity-fed and one with a pump for low invert sites. Here’s how it works:

1. Settlement Tank (Primary Chamber): In the first stage, heavy solids settle at the bottom, forming ‘sludge’, while lighter materials like oils and fats float to the top. This helps separate the wastewater.
2. Buffer Tank: This stage balances the flow of incoming wastewater using pumps to ensure the system handles load fluctuations effectively.
3. Biological Treatment Zone (Biozone): The submerged aerated filter provides a large surface area for microbes to break down organic matter. Aeration is regulated by the control panel for optimal efficiency, ensuring smooth operation without clogs or the need for chemicals.
4. Clarifier: In the final stage, bio sludge settles out, and airlift pumps recirculate it back to the settlement tank. The fully treated liquid is now ready for safe discharge.

This all-in-one system is ideal for commercial wastewater treatment for populations over 50, offering reliable, low-maintenance operation.

The key difference between a septic tank and a sewage treatment plant lies in how they process and treat wastewater:

1. Septic Tank: a basic system that primarily separates solids from liquids in the wastewater. It uses natural biological processes to break down the waste in an anaerobic environment (without oxygen). The liquid effluent then flows to a soakaway or percolation area where it is absorbed into the soil. While it reduces solids, the wastewater discharged is not fully treated, so it still has contaminants.
2. Sewage Treatment Plant: also called a wastewater treatment plant, this provides a more advanced treatment process. It not only separates solids from liquids but also introduces aerobic treatment (using oxygen) to further break down and treat the wastewater. This results in a much cleaner effluent that can be safely discharged into watercourses like rivers or streams, making it more environmentally friendly.

In summary, septic tanks offer basic wastewater separation, while sewage treatment plants provide a higher level of treatment that is more suitable for environmentally sensitive areas, larger populations and stricter discharge requirements.

Biochemical Oxygen Demand (BOD) is a key metric used to evaluate the amount of oxygen that microorganisms consume while breaking down organic matter in wastewater. It helps gauge water quality and the effectiveness of wastewater treatment processes.

BOD is essential for understanding water pollution levels. High BOD values indicate a large amount of organic waste, which can deplete oxygen levels in water bodies, potentially harming or killing aquatic life due to low oxygen availability.

Wastewater treatment plants use BOD testing to monitor waste loads and ensure compliance with environmental regulations. It’s also crucial in determining the efficiency of treatment processes and the impact of effluent on natural water bodies.

In wastewater treatment, sludge refers to the solid, semi-solid, or slurry materials that are left behind after wastewater has been treated. It is primarily made up of organic and inorganic materials, microorganisms, and water, and is a byproduct of both primary and secondary treatment processes. Proper sludge management is crucial for minimising environmental impact and reducing waste.

BS EN 125566-1 is the mandatory standard required for certification of a Septic Tank, BS EN 125566-3 is the mandatory standard required for certification of a Sewage Treatment Plant.

No, this is not true. All wastewater treatment tanks need to be emptied in accordance with the manufactures recommendations which is usually (desludged) once a year. The sludge remains in the tank and it is only the wastewater that is treated before it leaves the tank. You are entitled to one free desludge a year if you are paying rates and not connected to a main sewer in Northern Ireland. Call NI Water on 03457440088 to arrange a desludge or visit their online self service portal. 

On occasion, we have arrived to service a tank that has been deemed as emptied only to find that the tank is full of sludge. We cannot service the tank if it is full of sludge. The customer understandably tells us that their tank has been emptied – they saw the septic tank being desludged! We understand that the desludging company did appear to empty the tank but the tank has been emptied via the wrong access point and up to 4.5m3 of clean water has been removed instead of sludge! The sludge is still in the sludge chamber. 

Yes, you need to make sure your Tricel wastewater treatment tank is desludged using the sludge cap as an access point. We talk you through this during your installation process. The sludge cap is the smaller round green cap – this is the access point where the tank should be desludged annually.

The general guideline referred to by building control NI is the one used by the Environmental Health Services which is a minimum of 7 metres.