Chlorine dioxide monitoring after filter backwash water disinfection.
Legionella prevention by chlorine dioxide. Biofilm removal in pipes and filters. Monitoring chlorine dioxide concentration (0,6 and 3,0 mg/l ) in the backwash water according to DIN 19643-2 using Testomat 2000® ClO2
In order to avoid microbial contamination, DIN 19643-1 recommends that swimming pool filters should be backwashed twice a week regardless of how dirty they are.
Despite regular backwashing, biofilms will occur, the smaller the backwash intervals, the stronger the contamination and the biofilm formation in the filter material. Cleaning of dirty filter media requires very high free chlorine concentrations. Furthermore, chlorine reacts with the nitrogen carriers in the biofilm and leads to formation of chlorine amines and further pollution of the pool water. Sodium hypochlorite can be used as an alternative disinfectant and biofilm remover, but it not completely dissolve the biofilm. Sodium hypochlorite disinfection gives rise to secondary reactions that form poorly degradable organic halogen compounds (AOX) so that the limit values might be exceeded
Chlorine dioxide can be optimally used for the disinfection of the filter backwash water. Chlorine dioxide is a strong oxidizing agent, it is even stronger than chlorine. Chlorine dioxide in very low concentrations is uniquely efficient in destroying biofilm and bacteria. Our Testomat 2000® ClO2 allows you to monitor the chlorine dioxide level in the water .
Filter backwash using water from the splash container
Chlorine dioxide is pumped into the raw water pipeline using a dosing pump on the pump suction side. In this way, optimum mixing is guaranteed. The chlorine dioxide limit value of 0,6 mg/l is measured upstream of the filter by the Testomat 2000® ClO2. If you have several filters, only one Testomat 2000® ClO2 will prove to be sufficient as not all filters are washed simultaneously.
Filter backwash using water from backwash tank.
In order to avoid bacterial growth during stand still every backwash tank should be equipped with a circulation and a chlorine dosing system. It would be advisable to disinfect the backwash water using chlorine dioxide instead of chlorine dosage to maintain the concentration of chlorine dioxide in the backwah water at 0,6 mg/l using Testomat 2000® ClO2.
The standard DIN 19643-2 4.4.2. recommends increasing the chlorine dioxide concentration to 3,0 mg/l once monthly, in order to prevent biofilm formation in the backwash tank and pipe and so inhibit microbial growth in the filter.
Our Testomat 2000® ClO2 with an optional plug-in card for a SD-Card Data logger ensures reliable monitoring of the chlorine dioxide concentration and saves all measuring data and error messages on an SD-card making daily manual measurements unnecessary.
1 Adsorbable organically bound halogens : Chlorine, bromine and iodine compounds
Manual Testomat 2000® ClO2 Testomat 2000 CLO2 (1527)