Dunea

The western part of the Netherlands depends largely on river water from the Meuse and Rhine rivers for drinking water supply, which is infiltrated into Managed Aquifer Recharge (MAR) systems in the Dutch coastal dunes. Pre-treated river water is infiltrated through open basins and recovered after soil passage for further treatment. This soil passage is a crucial step in drinking water treatment where unwanted microorganisms are efficiently removed. Field studies by Schijven et al (1998,1999), among others, showed that log removal during saturated transport in these systems is more than sufficient to produce microbiologically safe drinking water. Nevertheless, in subsequent years, fecal indicator organisms were still found with some regularity in the abstracted water. It was suspected that this (re)contamination was caused by short circuit flow with feces-contaminated water from ground level through the unsaturated zone. Conducting several field experiments confirmed this hypothesis and provided unique insight into transport behavior and log removal in the unsaturated zone and the role of preferential flow under field conditions. Results of the field trials have been implemented in guidelines for design and management of MAR systems and whether to allow grazing livestock near the MAR-systems for nature management. In this contribution we present the results of a series of field trials, spanning 20 years, providing unique insight in removal of fecal indicator bacteria in unsaturated dune soils and increasing insight in processes responsible for recontamination of infiltrated river water. 

Pipe materials appear to play an important role in the development of biofilms in drinking water distribution systems. However, there is controversy as to whether pipe materials shape the composition and diversity of bacterial communities in biofilms. To investigate the long-term effects of pipe materials on biofilms, triplicate samples of mature biofilms on unplasticized polyvinyl chloride (PVC-U), grey cast iron and asbestos cement (pipe age > 40 years) were obtained from three areas of an unchlorinated drinking water distribution system in the Netherlands. Illumina sequencing was performed and 773 OTUs (730 OTUs-814 OTUs) were detected within the biofilms on the three pipe materials, all of which were dominated by Proteobacteria (36.2%-46.1%). Both the alpha and beta diversity results showed that the bacterial communities of the biofilms formed on different pipe materials were highly similar. The neutral community model revealed that the assembly of the biofilm communities was governed by environmental selection rather than neutral processes. Among the 142 shared OTUs between the water and biofilm samples, there were 25 enriched OTUs (e.g., OTU7, assigned as Nitrospira spp.), which accounted for 62.6% of the total sequences, while 16 OTUs were disadvantaged (e.g., OTU14 and OTU40, assigned as Hyphomicrobiaceae), accounting for 2.2% of the sequences. Based on the findings, we propose and discuss a harmonisation process by which biofilms with significant differences due to the pipe material harmonize over time resulting in biofilms with similar bacterial communities. Our findings provide valuable insights into long-term biofilm development, bridging an essential gap in our current understanding of the influence of pipe materials on biofilm communities. These findings also highlight the importance of long-term studies and point to a potentially masked harmonizing process during biofilm development over years/decades.

Aeromonas is included in the Dutch Drinking Water Decree as an indicator for elevated microbial regrowth in non-chlorinated drinking water distribution systems (DWDS). The temporal and spatial diversity of Aeromonas species in ten DWDS and their planktonic growth characteristics for different carbon sources was investigated. Genotyping of the gyrB gene of isolates showed a non-systematic temporal and spatial variable prevalence of seven different Aeromonas species in these DWDS and no correlation with AOC-P17/NOX and Aeromonas concentrations. Pure cultures of these seven species showed a high affinity to low concentrations (μg/L) of individual amino acids and fatty acids, compounds associated with biomass. Growth occurred at 0.5 μg-C/L of an amino acid mixture. Growth of a mixed community of A. rivuli, A. salmonicida, A. sobria and A. veronii in drinking water occurred in pasteurized samples, however, no growth and decay occurred in competition with the autochthonous bacteria (non-pasteurized samples). This community also failed to grow in non-pasteurized distribution samples from a location with clear increase in planktonic Aeromonas concentrations in the transported drinking water. For competitive planktonic growth of Aeromonas an amino acid concentration of ≥5 μg-C/L is required. AOC-P17/NOX concentrations showed that such concentrations are not expected in Dutch drinking water. Therefore, we suspect that competitive planktonic growth is not the major cause of the observed non-compliance with the Aeromonas standard in non-chlorinated DWSD.Importance The occurrence of the bacterial genus Aeromonas in non-chlorinated drinking water in the Netherlands is regarded as an indication for elevated microbial regrowth in the distribution system. Identification of the prevalent species in ten distribution systems by genotyping yielded seven different species, with A. rivuli, A. veronii and A. sobria as the most dominant ones. Planktonic growth experiments of pure cultures confirmed former published affinity of Aeromonas for certain biomass compounds (amino and fatty acids). In competition with the autochthonous microflora, however, planktonic growth was not observed, only after addition of a threshold amino acid concentration of 5 μg-C/L. Based on our results and further observations we deduced that planktonic growth of Aeromonas in the DWDS is not very likely. Benthic growth in loose deposits and planktonic release is a more plausible explanation for the observed planktonic increase of Aeromonas.

Abstract. Advanced oxidation with O3 / H2O2 (peroxone) was conducted on pilot plant scale on pre-treated Meuse river water to investigate the conversion of organic micropollutants (OMPs) and the formation of bromate. Fourteen selected model compounds were dosed to the pre-treated river water on a regular basis to assess the efficiency of the peroxone process and to establish the influence of the water matrix. The ozone dose was the main factor in the conversion of the model compounds, however, the ozone dose was limited because of bromate formation. The hydrogen peroxide dosage had only a minor effect on the conversion, but it limited the bromate formation effectively. In terms of limited chemical consumption, maximal conversion and to comply the strict Dutch drinking water act for bromate of 1 μg L−1, a practical peroxone setting was 6 mg L−1 hydrogen peroxide and 1.5 mg L−1 ozone. During the investigation period, the average conversion of the model compounds was 78.9 %. The conversion of OMPs was higher at higher water temperatures and lower concentrations of DOC and bicarbonate. The bromate formation also was higher at higher water temperature and lower bicarbonate concentration and proportional with the bromide concentration, above a threshold of about 32 μg L−1 bromide. The peroxone process can be controlled on basis of the (derived) parameters water temperature, bicarbonate and DOC.

Failure data are a valuable source of information on the condition of underground assets. Systematic registration of relevant items on cause, nature and circumstances of each occurring failure is, however, complicated in day-to-day practice. Moreover, in a network of limited size it takes a long time to obtain a statistically relevant amount of data. Dutch water companies in collaboration with the KWR Watercycle Research Institute have joined forces and developed a data standard and central database to store and analyse failure data. As of early 2012, 66,000 km of network are monitored, providing around 2,500 records on failure annually. All in all it provides solid information needed for strategic asset management that helps to support well established asset management plans.

In western Europe, large and important coastal dune systems exist, consisting of complexes with parabolic dunes, transverse dunes, etc. In The Netherlands, as in other parts of Europe, dunes are in a phase of stabilization. Mobile dunes in these systems, however, are extremely rare. At least part of the stabilization of dunes is the result of human interference with dynamic dunes over the past centuries, for example, in the large-scale plantations with pine trees. Currently, managers recognize that geomorphological stability in coastal dunes will eventually lead to a loss of biodiversity. Because of a change in coastal defense strategies since the 1990s, blowing sand is no longer seen as a threat, but as a chance for landscape rejuvenation. At the end of the century, several experiments started to destabilize dunes, in order to create new chances for pioneer situations. However, climate change, especially in the last few decades, does not favor dune mobility, causing a significant increase in rainfall, a rising temperature, and consequently a longer growing season. Also nitrogen input, derived from air pollution, continues to fertilize dunes over several decades, giving rise to much stronger vegetation growth compared with undisturbed sites. Thus, the question is: does mobilizing dunes provide possibilities for long-term landscape management, or does it just impose some short-term disturbances that inevitably fade out within a few decades? In this chapter we discuss the mechanisms of dune mobility in temperate climates, the possibilities the nature managers have of interfering with these mechanisms in order to obtain their biodiversity goals, and the interaction with coastal defense strategies.

Organic micropollutants (OMPs) are detected in sources for drinking water and treatment possibilities are investigated. Innovative removal technologies are available such as membrane filtration and advanced oxidation, but also biological treatment should be considered. By combining an advanced oxidation process with managed aquifer recharge (MAR), two complementary processes are expected to provide a hybrid system for OMP removal, according to the multiple barrier approach. Laboratory scale batch reactor experiments were conducted to investigate the removal of dissolved organic carbon (DOC) and 14 different pharmaceutically active compounds (PhACs) from MAR influent water and water subjected to oxidation, under different process conditions. A DOC removal of 10% was found in water under oxic (aerobic) conditions for batch reactor experiments, a similar value for DOC removal was observed in the field. Batch reactor experiments for the removal of PhACs showed that the removal of pharmaceuticals ranged from negligible to more than 90%. Under oxic conditions, seven out of 14 pharmaceuticals were removed over 90% and 12 out of 14 pharmaceuticals were removed at more than 50% during 30 days of experiments. Under anoxic conditions, four out of 14 pharmaceuticals were removed over 90% and eight out of 14 pharmaceuticals were removed at more than 50% over 30 days' experiments. Carbamazepine and phenazone were persistent both under oxic and anoxic conditions. The PhACs removal efficiency with oxidized water was, for most compounds, comparable to the removal with MAR influent water.

UV/H2O2 advanced oxidation is an effective barrier against organic micro pollutants. Several studies have focused on the degradation of a wide range of pollutants, but regarding the comparison of low-pressure mercury lamps (LP) with medium-pressure mercury lamps (MP) with respect to energy consumption by the UV/H2O2 process, little is known so far. Although the absorbance of H2O2 at 254 nm is low, the results of this research show that the yield of hydroxyl radical formation (OHCT) with LP lamps is comparable or higher than with MP lamps. In a water matrix with a background absorbance due to organics and nitrate, H2O2 absorbs UV light very effectively at 254 nm. Generally, due to the contribution of direct photolysis, the degradation of pollutants is better with MP-UV/H2O2 than with LP-UV/H2O2 at the same UV fluence. Therefore, with LP-UV/H2O2 micro pollutants are predominantly degraded through reaction with OH radicals. However, due to the much higher efficiency of LP lamps in converting electrical energy to UV-C light, the energy required to achieve 90% degradation (EEO) of pesticides and pharmaceuticals can be significantly lower with LP-UV/H2O2 than with MP-UV/H2O2. Results of bench-scale tests show EEO data of the LP-UV/H2O2 process to be 30%–50% lower than for the MP-UV/H2O2 process. At these process conditions MS2 phage inactivation was found to be more than 8 logs for both MP-UV/H2O2 and LP-UV/H2O2.