Interview: our CLO Frank Mullins on wastewater compliance

Cathal Walsh
Environmental Journalist
Monday, 1st July 2019
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Frank talking to a group of people

Table of Contents

I recently had a one-to-one talk with Frank Mullins, our Chief Laboratories Officer. With a wealth of experience in water analysis and a particular interest in wastewater, he gave me a great insight into the importance of effluent treatment and the current situation with wastewater compliance in Europe.

1) What is wastewater testing?

When you have any domestic or industrial waste from either households or from businesses they all have to go to a wastewater system. Irish water and the EPA would be responsible for making sure it is treated appropriately. Wastewater testing is performed to confirm that the right levels have been achieved following wastewater treatment. If you’ve got a wastewater treatment plant what would flow into that would come from a household or a business. The wastewater testing would be testing the water after it is treated. Anything from suspended solids, BOD’s, COD’s and pH and ammonia content. What you’re looking to do is make sure you’re following the correct methods and your wastewater treatment has been successful.

2) In what sort of areas/premises would you mainly carry out wastewater analysis?

A treatment plant could be taking in your wastewater from a big area. They operate mainly out of urban areas. You can have them everywhere really depending on population.   They work towards keeping with certain parameters by removing impurities through chemical treatment.  The location is dependent on the population.  You see them scattered all around the country.


3) What is the biggest excess of a parameter you have seen in wastewater analysis?

The very principle of wastewater treatment focuses on suspended solids. When your wastewater goes to treatment it goes from being a wastewater to being an effluent. What an effluent is , is what is released into your local river, sometimes it is used for drinking water but most of the time its just sent out into your local river or lake.  The suspended solids must be reduced but more importantly it must be be treated so that it does not have a deleterious effect on the ecosystems in the river/lake waters.  Oxygen content, or rather the demand by oxygen consuming organisms to break down organics in effluent is extremely important.  To meet compliance limits, the aim is to treat the wastewater so that the chemical oxygen demand (COD) and the biochemical oxygen demand (BOD) of the effluent won’t compromise the eco-systems of the water.  When I’ve tested wastewater in the past, what I’ve seen is that when the treatments have failed, your suspended solids would be quite high, your BOD’s would be quite high, your COD’s would be quite high. You’re pH may also be out of range but generally where the treatment systems have failed the main exceedances you would see would be with BOD’s, COD’s and suspended solids.

4) Is it too high or too low oxygen that kills aquatic life? Or both?

Basically what you’re looking for is a balance. It’s all about balance. You can have it too low or you can have it too high.  For this test, we measure the dissolved oxygen in water. You’d have a specific range where you won’t have any impact on the eco system. If you go well above a certain levels, let’s say you have a BOD of 1000, that sample is very dirty, it’s smelly and it will have a negative impact on the eco system.  If you measured the dissolved oxygen of water  and its reading 1 or 2… up as far as 7 or 8 then you would be looking at possible fish kills and things like that.  You’re looking for that balance where the dissolved oxygen won’t have any negative impact on the river and its ecosystems. Fish and other aquatic organisms are just like us. They need to breathe oxygen in balanced healthy concentrations. Many people would know that the air we breathe has approximately 20% oxygen. The equivalent life sustaining concentration range in rivers and lakes is 4 – 15 mg/L depending on the aquatic life present in the river.

5) What sort of damage would that excess do to the environment?

You’d be worried to some degree about the quality of the soil but to a larger extent the little bugs that live in the soil.  So from the macroscopic scale we consider  what are known as the macro-invertebrates.  What oxygen is available in that river can be largely affected by a single wastewater emission point. Therefore, it can dictate what communities of macro-invertebrates can survive in these areas. This in turn affects the food-chain in that river.     Aside from fish and macro-invertebrates, algae and vegetation also grow underwater and on the water surface.  If your phosphate level in the water is quite high then it can promote the growth of algae and that affects the whole natural habitats. From a scientific perspective, there’s competition for oxygen in the water and a competition for food. In the worst case scenario, where untreated wastewater has contaminated the water, then that can start a negative chain reaction in the water.   That’s why there’s so much emphasis on  removing pollutants from effluent. The health of our rivers and lakes depend on it.



6) Is there a problem with wastewater compliance in Ireland?

Basically wastewater is any water that has been used by a human for washing, sewage or industry. When you have that going out into your local river and it is not being treated correctly you’re going to see problems appear in our natural surface waters..  The main issue all over Ireland in my opinion is that with increasing populations , the wastewater treatment plants haven’t maintained the facilities to treat the water to the correct level.  The populations have grown at such a rate in certain areas that the wastewater treatment plants haven’t been able to grow at a fast enough pace to keep up.  There’s an awful lot of treatment  plants around the country that need upgrading.

Boyle in Roscommon is a good example of a water treatment system that has not worked.  The maintenance and modernisation of the water treatment plant hasn’t kept pace with the population growth in the area. It doesn’t matter a huge amount if techniques have changed or not, it is the sheer capacity of water treatment that’s causing issues. Ireland does have an issue with wastewater treatment plants purely for that reason.

When you see beaches being closed around the country it is usually due to bacteria in the water, you may be able to trace that back to a failure in a certain wastewater treatment plant ( as an example see this recent article for a beach in  Dublin) . When you have faecal matter being found in local beaches it is usually due to a waste water treatment plant not operating correctly.

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