A pilot plant study on the behaviour of ethylene diamino- tetraacetic acid (EDTA) during groundwater recharge of river water confirmed that EDTA is nondegradable under anaerobic and subtoxic conditions and partially degradable under aerobic conditions. The degree of aerobic degradation showed to be dependent on EDTA concentrations and temperature. At concentrations of about 500 mug EDTA/l, at a retention time of 15 days in the recharge bed, the removal was approx. 60% at a temperature >10 degrees C and approx. 30% at a temperature < 10 degrees C. At concentrations of tens of mug/l, i.e. the present maximum concentration level in the water of the rivers Rhine and Meuse, the removal was approx. 33% at a temperature >10 degrees C and approx. 15% at a temperature <10 degrees C. At concentrations of 7 mug/l no removal was found. The most serious consequence of the pollution of river water by EDTA for the drinking water supply using dune or bank recharge appears to be the adverse effect on the removal of heavy metals, respectively their mobilisation during the recharge. From the studied heavy metals (Cd, Cu, Ni, Pb, Zn) the most profound mobilisation effects have been found for Pb, Ni and Cu. The mobilisation of Pb has been found by the recharge in the dune sand contaminated by suspended solids from river water. The mobilisation was substantially higher during winter than during summer. In winter at a EDTA concentration of 500 mug/l the mean Pb concentration in the effluent of the recharge tank exceeded the WHO drinking water quality guideline of 10 mug/l. Based on the varations of phosphate concentrations in the effluent of the tank, it has been suggest that the seasonal differences in the mobilisation effects were caused by the formation of highly insoluble Pb5(PO4)3Cl. Mobilisation effects for Cu and Ni were found already at a concentration as low as 90 mug EDTA/l.

This report gives an overview of the present state of quality assurance in the drinking-water production in the Netherlands in 1996. The Netherlands Inspectorate for the Environment carried out an investigation at 49 drinking-water companies. The process of drinking-water treatment was examined using a checklist with special attention for quality assurance and hygienic aspects, safety, and communication and environmental aspects. Most of the companies stood on the side of quality assurance according to existing procedures ; employees were enthousiastic and well versed. Especially the technological and analytical aspects are well organised. However, still much work has to be done to reach the level of an accepted quality assurance system.<br>

The objective of this study was to estimate the use, emissions and aquatic fate of lindane in the Rhine Basin from 1985 to 2000. The use of lindane in the Rhine Basin is based on its agricultural use in the five most important riparian states: Germany, Switzerland, France, Luxembourg and the Netherlands for 1985 and 1990. Based on anticipative measurements on the different uses in these countries, hardly any change was to be expected in the period 1990 - 2000. Monitored data up to 1993 more-or-less confirm this assumption. Six major emission pathways are distinguished: 1) agricultural applications, 2) erosion, 3) domestic use, 4) atmospheric deposition directly onto surfacewaters, 5) atmospheric deposition via non-paved areas and 6) runoff from urban areas. In 1985 agriculture and atmospheric deposition together comprised over 70% of all emissions whereas in 1990 households and agriculture were calculated to be responsible for almost 80% of all emissions inside the Rhine Basin. The aquatic fate in the Rhine Basin was calculated with the water quality model DELTAWAT. Comparison of the calculated with the observed water quality shows in general an overestimation of the emissions in 1985 by a factor ranging from 1 to 2, whereas the estimates for 1990 looked fairly accurate. Since the monitored discharges showed unexplainable discrepancies, further analysis of the emission estimates was not very useful. Assuming an overestimation of the sources by a factor of 1 to 2 in 1985 and of the 1990 emission estimates within a range of 50%, the 50% emission reduction objective of the International Commission for the Protection of the Rhine (ICPR) in 1995 in comparison with 1985 has most likely already been met. The water quality objective for the year 2000, however, will most certainly not be met or even be approached in most parts of the Rhine Basin. The ICPR objectives for emissions and water quality seem to be in conflict.

Using the database documented in the TNO/RIVM report, 'Calculations of atmospheric deposition of contaminants on the North Sea', additional data on the emission of some substances to air were collected and their subsequent contribution emissions to air were collected for some substances, and their subsequent contribution to the total load via atmospheric deposition onto the North Sea and Netherlands inland waters evaluated. The percentages with which emissions to air will have to be reduced to reach the environmental quality target were calculated, leading to the following conclusions: 1) Atmospheric deposition is an important source of pollution in both the North Sea and the Netherlands' inland fresh waters, especially for the case of persistent organic substances (PAH, PCB and pesticides). The contribution increases when run-off and seepage are taken into account, mainly in the case of nitrogen. 2) The contribution of emissions to air in the Netherlands (via atmospheric deposition) to the total load in the North Sea, and inland surface waters , is small. 3) Emissions of PAH and PCB to air in the Netherlands contribute about 10% to the total load in the North Sea and inland surface waters. 4) Although the contribution of the Netherlands' emissions to air via atmospheric deposition onto the Netherlands' inland waters is small, the Netherlands is a net exporter of pollutants via air emissions. 5) Emissions to air in the Netherlands contribute substantially to the pesticide load of the North Sea and inland waters. 6) Atmospheric deposition of heavy metals decreases by 10-20% from 1990 to 2000, with the exception of lead, which decreases by 50-60% in the same period. 7) Atmospheric deposition of PAH decreases by only 20% from 1990 to 2000. 8) The uncertainty in the calculations varies with the pollutant studied. Heavy metals are under- or overestimated by 20-50%; NOx by 30%, PAH by 200% and pesticides by 500%.<br>

Research into water consumption by various consumer categories is at present being carried out to support and sustain implementation of the governmental policy . In this overview of the results of water abstraction analyses and demand in the Netherlands, emphasis has been put on quantitative aspects. In general terms, water use can be divided into consumptive uses, of which a significant share of total supply does not return directly to its source (i.e. household, industry, agriculture) and non-consumptive uses, of which practically the entire volume returns to surface water or groundwater (e.g. cooling). In 1996 around 12,000,000,000 m3 groundwater and surface water were abstracted. Of the total abstracted water, around 54% was fresh and the rest was brackish/saline water. Of the total brackish/saline water, 70% was used as cooling water for electricity plants; this figure was 40% for fresh (surface) water. The total abstracted fresh groundwater in the Netherlands has been used for public water supply (69%), industry (15%), small businesses (4%) and agriculture (12%, mostly for sprinkling). Measured as specific water demand (litres per capita per day), domestic water use has increased. This happened especially between 1960 to 1975 (at 108 litres per capita per day). Since about 1990 it has decreased. In 1995 the level was 138 litres per cap. per day. Forecasts indicate a continuing population growth. Specific water demand is expected to decline; however, relatively little in the first ten years, reflecting the use of more water-saving appliances. Up to now industrial water demand was shown in relation to industrial production. The strong economic growth after 1960 introduced an increased water demand up to 1975. Stricter controls and charges on effluents encourage industries to reduce water demand. Forecasting industrial water is done on the basis of results from several branches of industry (e.g. paper industry) and the scenarios of the production level. The future production level of existing plants is taken from an economic model of the Netherlands Bureau for Economic Policy Analysis. All scenarios show a growth in the industrial water demand. Agricultural uses of water refer only to water supplied by the public water companies and direct water supply from groundwater abstraction, especially for sprinkling systems. Public water supply is important for cleaning some kinds of equipment (health aspects) and for livestock, although this use is expected to decrease in volume and in time due to diminishing livestock numbers.

This report discusses the various factors (Capacity controlling parameters) which determine the extent of storage of chemicals and the results of a workshop which dealt with prediction and modelling of Chemical Time Bombs (CTBs) related to heavy metal contamination. Combinations of inputs like acidification with deposition of metals from the atmosphere may cause an effect which is worse than each of them on their own. Important are those cases where the capacity of the soil/sediment to retain chemicals changes. Examples are changes in hydrology, changing land use and civil engineering works. Qualitatively we can predict under these circumstances thath the pH will change, organic matter content will changes etc. Also many models are available to predict the effect of single or a few parameters in heavy metals behaviour, but few if not any to predict the combined effects. For these dynamic changes we selected changes in hydrology and changes in land use as topics for the dicussion in the workshop. The last part of the workshops was devoted to constructing research proposals to fill in gaps in our knowledge.

Soil contaminants accumulating through food chains may exert toxic effects on birds and mammals (secondary poisoning). In the current procedure for setting soil quality objectives, the maximum permissable concentration for a chemical in the soil (MPC) for secondary poisoning is based solely on the food chain soil --> worm --> bird/mammal, and calculated with MPC(soil) = NOEC(bird or mammal) / BAF(worm), in which: BAF is the bioaccumulation factor and NOEC is the no-observed effect concentration. In the present study the above-mentioned algorithm is extended by: 1. including the major terrestrial food chains, 2. applying correction factors for NOECs to account for differences between laboratory and field conditions, 3. generating probability distributions for MPCs by treating BCFs, BAFs and NOECs as stochastic variables. Food webs are constructed for eight bird of prey species and two beast of prey species with different food choice. Six compounds are selected based on the availability of bioaccumulation and toxicity data: DDT, dieldrin, lindane, pentachlorophenol (PCP), cadmium and methyl mercury. Model calculations are made with average values for food choice and correction factors. The model can be adjusted to specific locations, seasons and life-stages by varying these input parameters. Literature data reveal that it is appropriate to correct for caloric content and assimilation efficiency of food types, as well as for metabolic rate of birds and mammals. The scarce information about pollutant assimilation efficiency and species sensitivity does not indicate the necessity to correct for these factors. Species feeding on birds (Sparrowhawk, Goshawk) and small carnivorous mammals (Buzzard, Barn Owl) are exposed to a much higher extent to the contaminants than species feeding on small herbivorous mammals (Kestrel, Long-eared Owl). The following recommendations can be made for procedures for derivation of environmental quality objectives based on the risk of secondary poisoning. The food chain soil --> worm --> bird/mammal can be used for terrestrial ecosystems. In case of persistent and highly lipophilic compounds, attention should be paid to top predators, especially birds, exposed through the pathways soil --> worm and insect --> birds --> top predator. It should be realized that for most chemicals, the risk-analysis for top predators is seriously hampered by a lack of QSARs and experimental data on bioaccumulation in invertebrate and vertebrate species. Corrections should be applied for differences between laboratory and field conditions concerning metabolic rate, caloric content and assimilation efficiency of food types. The correction for assimilation efficiency is quantitatively much less important as compared to corrections for metabolic rate and caloric content. NOECs, BCFs and BAFs should be used as stochastic variables when possible, providing valuable information about the variation in the calculated MPCs.<br>

The minister of Housing, Physical Planning and Environment has requested the RIVM to publish an annual Environmental Balance (EB) with an Environmental Outlook (EO) to appear every four years. Both of these will serve as the objective scientific basis for the development of the national environmental policy. The EB gives a description of the state of the environmental quality. The EO provides a long-term description of the environmental quality as a consequense of the implemented and proposed policy (measures), and explores policy options, including the relation to international developments.In this definition report indicators on which the status and development of one of the functions of fresh surface and groundwater "the drinking and industrial water supply are being proposed. Several criteria have been applied to select the most relevant indicators. Attention is paid to the monitoring of waterdemand and other indicators (diagnosis). Also an indicative outline of modelling is given (prognosis). In the last part of this report an indication is given of necessary activities, especially in the next year.<br>

Concerns an inventory on the densities of Cryptosporidium and Giardia at three sites in both large international rivers in the Netherlands, River Rhine and River Meuse. Mean densities, corrected for the recovery of the detection method, were similar in both rivers. Judged by all microbiological water quality parameters, except for Cryptosporidium, the quality of the River Meuse water improved after the river entered the Netherlands. For domestic waste water, all major point sources of both treated and untreated waste water are localised. The untreated waste water discharges by several Belgian cities appear to be important pollution sources for the River Meuse.

The use of models developed for the emission (PROMISE) and dispersion (WATNAT) of substances to surface water is explored for the quantitative description of the emission and dispersion of enteroviruses to surface water. Modelling of the emission gave the contribution of the discharge of enteroviruses by treated and untreated domestic wastewater. According to the calculations the emission of enteroviruses can effectively be reduced by further reduction of direct discharge. To recommend measurements for improvement of watewater treatment data about the efficiency of the removal of enteroviruses are insufficiently available. Modelling of the dispersion of enteroviruses in surface water gave concentrations of enteroviruses that were very similar to measured concentrations in the large rivers. However, the calculations are still too uncertain to be able to draw conclusions concerning the quality of water for recreational purposes or for the drinking water supply. The modelling can be improved by measuring concentrations of enteroviruses in the Meuse at Eysden, in the Rhine at Lobith, in raw sewage and after wastewater treatment.<br>