Disinfection by-products (DBP) - Problem and remedies

When disinfectants react with impurities in bathing water, unwanted chemical contaminants called disinfection by-products (DBPs) are produced. In the case of chlorination of bathing water, it is mainly chloramines (bound chlorine) and trihalomethanes (THMs) that cause problems. These pollutants are harmful and should be kept as low as possible.

Other relevant by-products are AOX (adsorbable organic contaminants) and chlorate. Chlorate mainly enters the system if old chlorine solution is used and has been recognised recently and also added as a limit value in the DIN standard for bathing water.

The basis for the reduction of by-products

In addition to the importance of bathers washing before bathing, the basis for by-product reduction is a well-functioning flocculation filtration and the lowest possible disinfectant content. As bound chlorine and THMs are in true solution in the water, it is difficult to filter out these contaminants on their own and often the treatment plant has to be reinforced with technologies that provide strong adsorption and/or oxidation.

adsorption

Adsorption is effectively carried out using activated carbon in some form and oxidation is carried out using UV irradiation or ozonisation. Often these techniques are combined for best effect. Good hygiene before swimming pool bathing is a basic rule to prevent the formation of unwanted chlorine by-products.

"Pool bathing and health risks, rules and care".

Extract from the Public Health Agency of Sweden's handbook: Chemical contaminants in bathing water are unavoidable. They come largely from the bathers themselves. Dirt on swimwear and skin, skin cells, hair, skin oils, sweat, urine and faeces are some examples. In addition, skin creams, suntan oils, make-up, deodorants, soap and shampoo residues are added. Cleaning and maintenance products and dirty water can also enter the bathing water. Especially in outdoor pools, soil and dirt can easily follow bathers when they enter the water. Contaminated rainwater can also enter the pool. Furthermore, gaskets, sealants and caulking can be a source of contamination.

Not the primary pollutants that cause problems.

It is usually not the primary pollutants that cause problems. Instead, they provide a basis for the growth of micro-organisms or for chemical reactions. Water, heat and disinfectants are factors that can easily trigger chemical reactions and form new pollutants that can affect the formation of new pollutants, which can affect humans but also be negative for the environment. In particular, there are two different groups of chemical contaminants to be aware of that can be formed in bathing water if chlorine is used as a disinfectant: trihalomethanes and chloramines.

Remove the problem - not just the metric

The THM and AOX limit values act as indicators for the enrichment of organic halogens. Activated carbon adsorbs all forms of by-products, not just the indicators. Therefore, activated carbon is the safest technique to minimise THMs. Over time, activated carbon will become saturated with organic matter and will eventually lose its ability to reduce THMs, although the ability to reduce bound chlorine may remain. With the AKP method, new carbon is always dosed and the amount is adapted to the needs - therefore the AKP method is effective for the reduction of THMs and AOX.

Lower operating costs and improved water quality

• AKP removes the chlorine smell and minimises bound chlorine,
• THM and AOX
• Complete equipment for carbon powder dosing according to DIN 19643-2
• Dosage 0.3-2 g/m3
• Flushed out during normal backwashing
• Dosage approx. 2-5 g / bather
• Dosed when needed

ProPac - activated carbon powder dosing equipment

• can be used to advantage for
• Sand filters in pressure or suction mode with deep bed filtration
• Open sand filter
• Powder filters in pressure or suction mode (vacuum diatomite filters)
• Ultrafilter