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Falling foul of trade effluent consent: is biological treatment the answer?

By: Pete Cranney on Sep 15, 2023

For industrial manufacturers and processors, ensuring trade effluent discharges meet strict water company standards, particularly for chemical oxygen demand (COD), presents an increasingly complex challenge.

Trade effluent charges have increased significantly over the past decade and water companies, themselves under unprecedented pressure to limit environmental impact, are tightening permit conditions to drive industrial customers to improve the quality of water entering the sewers.

Existing trade effluent treatment methods may no longer be enough to meet required stricter standards. For industries already hit hard by rising energy, supply chain and production costs, new process requirements potentially pose another financial burden.

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Designed and implemented correctly, onsite biological treatment can deliver full environmental compliance and ensure long-term cost efficiency, while contributing to companies’ sustainability goals - another factor many businesses are now considering.

What is trade effluent?

Trade effluents are liquid waste streams discharged into public sewers from businesses and industrial processes. Their composition is highly variable but may include substances such as chemicals and fats that can be harmful to the human health and the environment if not treated correctly.

In giving consent for businesses to discharge trade effluent, water companies may require it to be treated to a specified standard before it enters the foul sewer and becomes the responsibility of the utility to manage.

A breach of trade effluent consent is a criminal offence and penalties can range from an early-warning notice to a fine or prosecution or, in the most serious cases, imprisonment.

Financial and reputational implications are also significant. The cost of mitigation for the most serious breaches, such as clean-ups or tankering, can potentially run into millions. They also risk thrusting the company brand into the spotlight for the wrong reasons.

Which polluting parameters are measured in trade effluent?

Specified trade effluent limits are usually for pH, flow, suspended solids, temperature and COD, which is a water quality measurement. Limits on COD concentrations in discharges to sewers can be particularly challenging to maintain, partly because they are highly variable, with spikes and dips depending on flows. Because of the additional costs incurred by the water companies to treat, heavy metals in the discharge are also being covered by consent limits, or being tightened if already included.

Industrial companies are likely to already have some level of wastewater treatment onsite, such as dissolved air flotation (DAF) systems, but many are now finding they require additional processes to keep COD within permitted levels and satisfy water companies.

Historically, tankering the waste away from site to be managed elsewhere may have been the answer, but this comes at a significant financial cost, as well as the heavy environmental impact associated with the mileage of carbon-emitting vehicles on the road.

When is biological treatment an option?

Installation of a biological treatment plant could be the most effective option to ensure full compliance. Many industrial trade effluents, particularly from the food and beverage sector, are ideal for biological treatment.

Wastewater generated by food and drink production is typically rich in organic materials like fats, oils and sugars, so can be treated successfully without chemicals once solids have been removed.

Biological treatment uses microorganisms to naturally degrade and transform organic pollutants without the use of chemicals. This approach reduces chemical residues, promoting a greener and more sustainable wastewater treatment process.

Some effluent from chemical and engineering sectors, among others, may also be suitable for biological treatment – it is always worth asking your supplier who will carry out tests and trials to ascertain effectiveness.

Biological treatment methods include:


The aerobic treatment process uses oxygen to break down the organic contaminants in an aerated tank. Oxygen is continuously mixed into the wastewater by an aeration device, such as a blower.

Aerobic microorganisms convert the pollutants into carbon dioxide, water and biomass. This process produces sludge which can be safely disposed of or sold as agricultural fertiliser.


Anaerobic treatment is energy-efficient process that uses anaerobic bacteria to convert organic pollutants or COD into biogas, a valuable source of renewable energy.

Submerged aerated filter (SAF):

SAF systems use a biological filter bed that supports the growth of microorganisms. The filters are continuously aerated to enhance the biological treatment process, allowing the microorganisms to effectively break down organic pollutants.

High-performance aerated filter (HiPAF):

HiPAF systems combine the benefits of SAF technology with enhanced aeration to achieve higher treatment efficiencies.

Lab tests and trials

Before permanent biological treatment is installed, advanced testing is available to ensure the most suitable system is selected.

Industrial effluent composition is highly variable and biological treatment processes should be tailored for each site. To inform this process, ahead of permanent installation, WCSEE can undertake in-depth advance testing in two ways - laboratory testing and onsite trials.

These detailed reviews can avoid performance and commercial shocks caused by discrepancies between designs and the delivery of a project. They also give clients reassurance that the systems are suitable before committing to a capital purchase, whilst at the same time keeping your site compliant.

Laboratory service

Bespoke lab-scale reviews ascertain the profile of the effluent and ensure that the correct process is implemented, based on the requirements of trade effluent permits.

A report is produced that determines the best technology and cost of the final scheme. This kind of testing has a quick turnaround, causes little disruption to the customer, and allows designers to rule out different technologies, saving time in researching options that might not work.

Onsite trials

Following the lab review, an onsite trial is usually recommended to identify the precise equipment required. Trials give a very accurate indication of how the plant will operate together with the running costs, giving the customer confidence that there will be no surprises. They can initially seem expensive, but they may save money in the long run, with a quick return on investment.


As trade effluent disposal costs rise, businesses in industries such as food and drink processing must explore solutions that are more cost-effective and environmentally-friendly. By considering biological treatment, companies can reduce costs, minimise environmental impact, and remain competitive in a challenging market landscape.

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Topics: Wastewater Treatment

Pete Cranney

Written by Pete Cranney

Pete Cranney has worked for Atana (now part of WCSEE) since 2003 and has experience across every part of the business. Specialising in food & drink manufacturing, Pete can recommend the most practical and cost-effective treatment processes, designing onsite solutions that achieve strict discharge consents. In previous roles, Pete has managed full treatment plants for clients such as PepsiCo and Kraft Heinz. He has also led on laboratory testing of client samples. In process design, Pete provides clients with the most effective blends of chemical and mechanical treatments to ensure their sites offer full environmental protection 24/7.

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