DIPool (Dutch Innovative Pool) - Advanced UV-based technology for pool water treatment

researcher: Maarten Keuten

Research objectives
Reduction of chemical disinfectants in public swimming pools. This can be done by combining alternative disinfection techniques with adapted water treatment in a new pool water treatment concept including aspects of hygienic control of pool visitors. The goal is to have chemical disinfectant free swimming pool water for public swimming pools.

Project outline
Introduction
The main disadvantage of chemically disinfected swimming pools is the formation of unwanted disinfection by-products (DBPs). Reducing DBPs by abandoning chemical disinfectants introduces new challenges for pool water treatment. The DIPool project investigates swimming pool water treatment without chemical disinfectants to face these challenges. The biological stability of swimming pool water, pool water treatment and the hygienic behaviour of swimmers was studied in 2014.

Approach
A pilot plant setup was used to focus on the pool water treatment at chlorinated and non-chlorinated swimming pool conditions (figure 1). The biofilm formation potential was determined with the use of membrane fouling simulators. Efficiency of treatment steps was also determined. The hygienic behaviour of swimmers was studied in cooperation with behavioural scientists from Twente University.

Figure 1 – Experimental setup DIPool for biological stability and treatment efficiency

Results
The biofilm formation potential was studied at different swimming pool conditions. Both chlorinated and non/chlorinated swimming pool water have low biofilm formation potential compared to tap water at 30°C (figure 2).

The use of biological filtration in both chlorinated and non-chlorinated pool water treatment improves the removal of nitrogen containing pollutants, which can be seen at the concentration of nitrate-n, which is more or less equal to the concentration of total nitrogen (figure 3). On the absence of a biological filtration, nitrogen containing pollutants are remaining which may lead to the formation of nitrogen containing DBP.

Hygienic behaviour of swimmers can be changed with the use of arguments. Pre-swim showering increased from 25-28% during the experiment with the use of carefully designed stickers (figure 4). The awareness on the importance of hygienic behaviour among swimmers needs to be improved to reduce the release of anthropogenic pollutants.

Figure 2 – Biofilm formation potential during chlorinated and non-chlorinated experiments

Figure 3 – Concentrations of NPOC, TN and nitrate-N during chlorinated and non-chlorinated experiments

Figure 4 – Sticker to improve hygienic behaviour of swimmers

Scientific relevance
Current pool water treatment relies on chemical disinfection. The development of a pool water treatment with alternative disinfection techniques is a new field of expertise. The influence of the dynamic bathing load on the water quality must be kept in control. Creating stable microbial pool water without the use of chemical disinfectants can lead to new viewpoints for comparable water treatment processes.

Social relevance
Since the early ages bathing and swimming play an important role in communities. The use of water basins changed over ages, while swimming has always been a social activity. Complaints about “swimming pool odour” and eye irritation are common reasons why nowadays some people never visit public swimming pools. UV-Disinfected swimming pools will provide healthy swimming without nuisance from disinfection by-products.

Literature

  • M.G.A. Keuten, M.C.F.M. Peters, H.A.M. Daanen, M.K. de Kreuk, L.C. Rietveld, J.C. van Dijk Quantification of continual anthropogenic pollutant release in swimming pools Water Research 53, (2014) p.259-270. 
  • M.G.A. Keuten, F.M. Schets, J.F. Schijven, J.Q.J.C. Verberk, J.C. van Dijk Corrigendum to “Definition and quantification of initial anthropogenic pollutant release in swimming pools”  Water Research 49, (2014) p.484. 
  • M.G.A. Keuten, F.M. Schets, J.F. Schijven, J.Q.J.C. Verberk, J.C. van Dijk Definition and quantification of initial anthropogenic pollutant release in swimming pools Water Research 46 (2012) p.3682-3692.