Biomedical subjects

H R Veenendaal

Publications and source records attributed to H R Veenendaal.

5 recordsLinked to original sources

PubMed2003

Elucidation and control of biofilm formation processes in water treatment and distribution using the Unified Biofilm Approach.

Controlling biological processes in water treatment and distribution is a major challenge to water supply companies. In the Netherlands, the use of chlorine-based disinfectants in water treatment is limited as much as possible and treated water is distributed without disinfectant residual in most cases. Biofilm formation processes in water treatment and distribution are studied using adenosinetriphosphate (ATP) as the parameter for active biomass. ATP measurements are applied to assess biofilm concentrations in distribution systems, in the biofilm monitor to determine the biofilm formation rate of treated water, in the biomass production potential test to determine the effect of pipe materials on microbial growth and in membrane systems to quantify biofouling. The use of a single parameter enables to compare biofilm concentrations in all situations and contributes to the understanding and control of biofilm formation processes in water treatment and distribution. This approach has been designated as the Unified Biofilm Approach.

Adenosine Triphosphate↗

PubMed1995

Bromate reduction by denitrifying bacteria.

In the presence of bromide, ozonation as applied in water treatment results in the formation of bromate, an ion with carcinogenic properties. The reduction of bromate by mixed bacterial populations as well as pure cultures was studied under laboratory conditions. Bromate was reduced to bromide by a mixed bacterial population with and without a preceding nitrate reduction step in an anaerobically incubated medium with ethanol as the energy and carbon source at 20 and 25 deg C. The predominating bacteria isolated from the batches showing bromate reduction were identified as Pseudomonas spp. Strains of Pseudomonas fluorescens reduced BrO(inf3)(sup-) to Br(sup-) but at a much lower rate than the mixed bacterial population did. Nitrate is a preferred electron acceptor for the bromate-reducing bacteria. Bromate reduction did not occur in the presence of NO(inf3)(sup-), and the rate of bromate reduction was at least 100 times lower than the rate of nitrate reduction. Bromate was completely converted to Br(sup-), indicating that intermediates, e.g., BrO(inf2)(sup-), did not accumulate during bromate reduction.

Journal Article↗

PubMed1985

A note on legionellas in whirlpools.

Water samples from 52 whirlpools (jacuzzi), water temperature 35-40 degrees C, and from 50 swimming pools, water temperature 8-30 degrees C, were investigated for the presence of Legionella pneumophila. This was isolated from 11 of 28 whirlpools with free available chlorine less than 0.3 mg/l. No legionellas were detected in 23 whirlpools with free available chlorine over 0.3 mg/l. Legionella pneumophila was found in two swimming pools. The results indicate that 0.3 mg/l of free available chlorine is sufficient to eliminate legionellas from whirlpools.

Legionella↗

PubMed1985

Influence of temperature on the number of Legionella pneumophila in hot water systems.

The occurrence of legionella in the hot water systems of two buildings (A and B) was investigated in relation to the water temperature. The peripheral parts of both hot water systems were found to be colonized by these organisms. A temperature of 60 degrees C in the hot water mains returning from the building eliminated legionellas from the mains as well as from the peripheral taps and showers. Legionellas could be isolated from taps, showers and the mains when the temperature in the return mains was kept at 54 degrees C. The hot water systems could not be completely decontaminated by raising the hot water temperature in the return mains to 70 degrees C combined with flushing all the taps and showers. It is suggested that failure to decontaminate the systems is due to dead ends in the pipeline network, which are not reached by the hot water and that these dead ends are the source for recolonization of the systems.

Hot Temperature↗

PubMed1983

Heat treatment as an aid for the isolation of Legionella pneumophila from clinical and environmental samples.

The isolation of legionella's from clinical as well as environmental samples is hindered by the overgrowth of legionella's by the accompanying bacterial flora, which could not be sufficiently suppressed by adding antimicrobial drugs to the BCYA alpha. The effect of heat treatment on clinical samples and on water samples concentrated by filtration was investigated. Treatment of the samples for 30 minutes at 50 degrees C reduced the number of cfu of the accompanying flora by a factor 10(1.6)-10(3.9) depending on the number of contaminants, whereas the number of cfu of legionella was reduced only by a factor 1.05-1.44. Higher or lower temperatures resulted in a too high reduction of the number of legionella's or an insufficient elimination of the accompanying flora respectively. The described method is less laborious and less critical than the earlier described low pH-treatment.

Hot Temperature↗