Disinfection by-products and microbial contamination in the treatment of pool water with granular activated carbon

Abstract

For swimming pools, it is generally agreed that free chlorine levels have to be maintained to guarantee adequate disinfection. Recommended free chlorine levels can vary between 0.3 and 0.6 mg/L in Germany and up to 3 mg/L in other countries. Bathers introduce considerable amounts of organic matter, mainly in the form of such as urine and sweat, into the pool water. As a consequence, disinfection byproducts (DBPs) are formed. Regulations in Germany recommend levels of combined chlorine of less than 0.2 mg/L and levels of trihalomethanes (THMs) of less than 20 microg/L. Haloacetic acids (HAAs), haloacetonitriles (HANs), chloropicrin and chloral hydrate are also detected in considerable amounts. However, these compounds are not regulated yet. Swimming pool staff and swimmers, especially athletes, are primarily exposed to these byproducts by inhalation and/or dermal uptake. In Germany, new regulations for swimming pool water treatment generally require the use of activated carbon. In this project, three different types of granular activated carbon (GAC) (one standard GAC, two catalytic GACs) are compared for their long time behaviour in pool water treatment. In a pilot plant operated with real swimming pool water, production and removal of disinfection byproducts (THMs, HAAs, AOXs), of biodegradable substances (AOC), of bacteria (Pseudomonas aeruginosa, Legionella, coliforms, HPC) as well as the removal of chlorine and chloramines are monitored as function of GAC bed depth. Combined chlorine penetrates deeper in the filter bed than free chlorine does. However, both, free and combined chlorine removal efficiencies decrease over the time of filter operation. The decreases of removal efficiencies are also observed for parameters such as dissolved organic carbon, spectral absorption coefficient, adsorbable organic carbon and most of the disinfection byproducts. However, THMs, especially chloroform are produced in the filter bed. The GAC beds were contaminated microbially, especially with P. aeruginosa. The contamination was not removable by backwashing with chlorine concentrations up to 2 mg/l free chlorine.

Antimicrobial and anti-biofilm effect of a novel BODIPY photosensitizer againstPseudomonas aeruginosaPAO1

“…P. aeruginosa colonizes human tissues, such as skin, eyes, and lungs, and its eradication may be complicated by the presence of multidrug-resistant strains (Nordmann et al 2007) and hypermutable variants (Oliver et al 2000). P. aeruginosa is also able to colonize and form biofilms, eg in the lungs of cystic fibrosis patients, in diabetic wounds, and on inert surfaces such as medical devices, prosthesis and catheters (Donlan 2001;Mittal et al 2009), in whirlpools and hot tubs (Mena & Gerba 2009), in filters (Uhl & Hartmann 2005), and in fan coil units (Liguori et al 2010). It is well documented that biofilms develop tolerance to antibiotics and biocides (Campanac et al 2002;Smith & Hunter 2008;Hoiby et al 2010).…”

Biologically active carbon filtration for haloacetic acid removal from swimming pool water

“…It is speculated that as residual disinfectants were removed by a greater extent at a longer EBCT, their negative impact on the established biofilm in the BAC could be minimal. Uhl and Hartmann (2005) found that the combined chlorine penetrates deeper in the BAC filter bed than the free chlorine does. The removal of HAAs may also benefit from the low concentrations of combined chlorine (0.16 ± 0.16 mg/L) in the pool water.…”

“…However, it is poorly documented on the removal of the less-volatile HAAs (Tang, 2011). Besides chemical processes such as Fe(0) reduction (Hozalski et al, 2001;Zhang et al, 2004;Tang et al, 2013) and UV irradiation (Weng et al, 2012), a typical biological process involves the use of a biologically active carbon (BAC) filter Xie and Zhou, 2002;Uhl and Hartmann, 2005;Tung et al, 2006;Tang et al, 2013) and the advantage of a BAC system is the ability of removing both precursors and HAAs which are firstly adsorbed into the macropores, where they are detained for the biological degradation by the attached bacteria (Kalkan et al, 2011). These findings, however, were largely based on bench-scale experiments from the treatment of dechlorinated water, and it is unclear whether the BAC filtration is applicable to the treatment of the chlorinated swimming pool water.…”

Evaluation of the effect of body fluid analogs on the parameters of nanofiltration during the purification of swimming pool water

“…However, the effectiveness of coagulation in the removal of micropollutants (especially the small-particle micropollutants) is low, on a level of 10-20% [11,12]. In addition, water treatment systems in many pool facilities still use single-layer sand filtration beds that do not ensure complete elimination of pathogens [13]. Improvement of the effectiveness of the filtration beds may be achieved by using an additional sorption layer of activated carbon.…”