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Are you using the right chemicals in your wastewater treatment plant?

By: Pete Cranney on Oct 13, 2023

Choosing and maintaining the right balance of chemicals for your wastewater treatment plant is vital to ensure it functions as efficiently and effectively as possible. But the unpredictable interplay of temperature, pH levels, contaminant content, equipment and process can suddenly find you in breach of agreed discharge consent levels without really knowing why.

How do you know whether to change your chemical package, plant design, process (or all three) to improve the efficiency of your operations and meet your discharge consent agreements? 

9 tips to ensure you have the right chemical treatment package

1. Understand your plant's condition

Before you make any decisions about your chemical treatment package, it’s essential to know exactly what’s going on inside your plant. Factors like temperature, pH, FOG content, COD, suspended solids, and the presence of sulphates and heavy metals can all play a vital role in chemical and mechanical effectiveness. So, test your discharge and commission a detailed lab report to uncover the current make-up of your effluent and how best to treat it. Knowing what you have to remove will dictate how you can remove it. 

2. Undertake jar testing

Jar testing is an invaluable tool in fine-tuning any chemical treatment strategy. This laboratory-based technique simulates treatment conditions and observes how chemicals interact with the effluent. You can pinpoint the optimal dosage and method for your plant's unique requirements through systematic trials and analysis. A report with details and photos explains exactly what you have now and what your new discharge numbers could be.

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3. Match the need with the solution

Various chemical treatment methods are available to address specific issues within your effluent. Each method serves a unique purpose, from pH neutralisers that bring balance, chelants and sequestrants that remove heavy metals, and anti-foaming agents that counter excessive frothing. Coagulants and flocculants come into play when dealing with suspended particles. Biological systems are needed to reduce soluble COD. Make sure you understand the purpose of each part of any suggested chemical treatment package so you’re not overdosing or underdosing against your specific needs.

4. Chemical selection and plant design go hand in hand

If you need a new plant or an upgrade to existing equipment, a new chemical treatment package should be designed to match your effluent, staffing, space and site requirements. Selecting appropriate chemicals is a complex process that requires a deep understanding of the chemicals themselves and how they interact with the plant design to minimise waste and maximise efficiency. Work with a reputable water engineering firm to create a full package optimised for your needs.

 5. Explore your options for chemical reduction

Is there potential to reduce your chemical usage?  

Shifting to more environmentally responsible solutions can contribute to your ESG goals and save you money in the long run.

Some organic coagulants are equally effective as some metal-based coagulants, and also have
the advantage of producing less sludge waste, reducing removal costs.

Re-designing your entire plant with chemical reduction in mind could:

  • Lower your ongoing treatment bills
  • Make operating your plant safer for staff
  • Reduce your reliance on non-renewable resources. 
  • Reduce waste, costs and carbon emissions.

6. Focus on monitoring, service & maintenance

Once a chemical dosing regime is in place, the support from your water engineering company should not disappear. Consistent monitoring of the performance of your chemical treatment package is essential to maintain the results you need.

Regular checks will ensure that your plant's conditions remain within the desired range and doses remain effective as volumes, processes and the potency of your discharge changes. This can be done automatically through monitoring equipment or service visits from an experienced engineer.

7. Ongoing testing will keep you within consent 

With regular laboratory testing of the raw and treated effluents, you can get a simple “removal percentage” on items such as TSS (Total Suspended Solids)  and COD (Chemical Oxygen Demand). This gives you a number that easily represents the efficiency of the plant, so quick action can be taken if the numbers start to drop.

Because of new advances and formulas, regular 6 monthly chemical reviews can highlight how a change in chemistry can increase performance or reduce costs without any equipment changes.

8. Changes to effluent may not be a result of failure of chemical treatment

A sudden failure of your discharge may be the result of equipment failure. As part of any investigation into a consent breach or dosing regime you need to audit all your physical equipment, too. There may be no need to address your chemical treatment package if the problem can be fixed by servicing or replacing pieces of kit.

9. Chemical treatment may not always be the most cost-effective option

If you have received a breach of consent notice, it’s easy to panic and agree to a chemical package you’re told can solve the problem. But, depending on the initial capex required and ongoing cost of the suggested solution, it may be more cost-effective to negotiate an excess for discharge consent. Ensure you have complete transparency from your engineering partner about potential return on investment and viable alternatives.

Chemical water treatments for heavy metal removal - an expert Q&A 


Selecting and implementing the right chemicals should be a unique process for every wastewater treatment plant. Differences in the space you have available, staffing requirements, and even the cleaning chemicals you use, will require different solutions.

Creating a chemical treatment package is a data-driven process that combines scientific understanding with practical application. By making informed chemical choices and employing tools like jar testing, you can maximise the success of a successful treatment strategy. Through monitoring and maintenance, you can ensure the continued efficiency of your plant while hitting your discharge consent. 

Why not choose an onsite chemical trial?

Whilst a laboratory-based analysis of your effluent gives a perfect snapshot of what the chemicals can achieve, running a trial of the chemistry on site over an extended period will give you much more accurate results. 

Cleaning equipment, shift changes, different hot and cold processes - all present different challenges to the treatment process, which won’t be evident in a single testing snapshot.

But an on-site chemical trial conducted over several weeks will show how a chemical regime will deal with all these different challenges, with site staff on hand to witness the results.  

A full flow trial (including the installation of portable equipment) will ensure the correct mechanical and chemical combination is applied before embedding new, or enhancing existing, wastewater treatment processes. 

After the trial, you can decide whether to continue to rent the equipment on-site, buy new equipment, or end the trial altogether.. Whatever your decision, you will have access to real-life data and a report showing the possibilities and costs involved.

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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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