Organic micro pollutants

Abstract

Since several decades organic micro pollutants (OMPs) have been detected in natural waters. Although appearing in very low concentrations (nanograms to micrograms per litre or even lower), the presence of more than 100.000 registered chemical substances in the European Union, of which 30.000-70.000 are in daily use, is a major reason for concern. Due to their persistent character the OMPs remain longer in the water cycle and can be transported over a longer distance than other pollutants. Current treatment facilities are not designed to remove those compounds, which causes them to end up in the environment and even in drinking water. The current problems on OMPs in the water cycle are not that the concentrations present in the water cycle are too high to guarantee the safety of drinking water, but are the long-term effects of these concentrations, the increase in concentrations (due to changing circumstances) and the unknown effect of OMPs in mixtures with other OMPs. In order to find a solution to this problem this project focusses on the following question: What is the most sustainable, applicable and cost-efficient strategy to reduce concentrations of selected micro pollutants in surface water and drinking water in the Netherlands? In this project various strategies to reduce the concentrations of OMPs are composed and scored by a Multi Criteria Analysis (MCA). The best strategy is tested on two case studies to see the influence of the strategy on the concentrations. The future situation regarding the emission of OMPs and discharge of river water is also taken into account. Whether the strategy is effective is determined based on limits of concentrations of OMPs. The scope of the project is on drinking water extraction areas in the Netherlands. Firstly a literature study on current European and Dutch legislation and policy, future trends regarding population growth, consumer behaviour and climate change and the presence and behaviour of target compounds in the water cycle is conducted. Based on the Deltascenarios two future scenarios regarding emission of OMPs, river discharge and precipitation are selected: REST and STEAM. Scenario REST is a scenario of economic stagnation with moderate climate change. In scenario STEAM both the economic situation and climate change increases. Later in the report these scenarios are used to test the best strategy on, which reduces the concentrations of OMPs in the water cycle. Dutch limits on OMPs in the water cycle only exist for a few compounds. For other compounds target values of other organisations are used. The found limits and target values are in the order of 0.1-1.0 ?g/L. The target compounds are selected based on an analysis of relevant compounds, which results in a limited number of compounds to elaborate on. Persistence of the compounds and availability of measurement data are important criteria in this analysis. The selected target compounds are carbamazepine, metformin, sulfamethoxazole (pharmaceuticals), iopromide (X-ray contrast agent), acesulfame-K, caffeine (domestic tracer compounds), MTBE (industrial chemical), AMPA, bentazone, glyphosate and N,N-DMS (pesticides). In surface water concentrations of the selected compounds between 0.025 and 83 ?g/L are measured. Found removal efficiencies in WWTPs and DWTPs vary between 0 and 98%, highly depending on the type of OMP, the used treatment techniques and the composition of the influent. Different strategies with different approaches within the water cycle are discussed, which are divided in source approach (use), mitigation approach (emission) and end-of-pipe approach (drinking water). Source approach: 1. Green pharmacy 2. Awareness in use and prescription 3. Legislation and policy 4. Green agriculture, greenhouse farming and cattle breeding Mitigation approach: 5. Separate collection of urine 6. Decentralised collection of wastewater in residential areas 7. Decentralised collection of wastewater in hospitals 8. Improvement of wastewater treatment plants End-of-pipe approach: 9. Improvement of drinking water treatment plants A MCA and sensitivity analysis are used to present the best strategy that is well balanced between all aspects of the water cycle and its users and which is sustainable, applicable, cost-efficient and which functions within European and Dutch legislation. The strategies are scored based on an expert judgement of the expert panel. The best two strategies are applied on water and mass balances of the two case studies to see the impact of the strategies. The first case study is the Bethunepolder between Amsterdam and Utrecht. This is a groundwater system. The second case study is the IJsselmeer area at Andijk, which is a surface water system. Both areas are partly fed by water originating from the river Rhine and serve as a drinking water extraction area. A water balance and, by multiplying the discharges by the measured concentrations, a mass balance of OMPs is composed. The results from the mass balances show whether or not the strategies are sufficient to decrease the concentrations to below the limits. Finally, a comparison between the two types of water systems (groundwater and surface water) is made. The MCA results in a highest score for the strategy ‘legislation and policy’. However, this strategy only holds when incorporating other measures to reduce the emission of OMPs into the water cycle (implementing stricter regulations results in the need for solution at the use or emission of OMPS, WWTP or DWTP). For this reason also a second best strategy is determined. Strategies 1, 2, 4, 8 and 9 are in the same range and score moderately, where strategies 1 and 2 score higher than the remaining three strategies. Although without a big difference with the third best strategy, the second best strategy is ‘green pharmacy’. All strategies with (de)centralised collection and treatment of urine or total wastewater score poor, due to a poor score on all three aspects: sustainability, applicability and cost-efficiency. Although, the systems in the two case studies are both partly fed by the river Rhine (via the groundwater and via the river IJssel), the measured concentrations and exceedance of limits and target values are not the same. In the Bethunepolder the calculated concentrations exceed the limits for six compounds, while none of the measured concentrations exceed the limits. In the Andijk case the calculated concentrations of five compounds exceed the limits, while for the measured concentrations these are only three substances. The future scenarios regarding the emission of OMPs and the discharge of river water are not influencing the (non-) exceedance of the limits. After applying the strategies on the models in the Bethunepolder case concentrations of most compounds decrease to below the limits, where this decrease is in the Andijk case not enough to go below the limits. For both case studies the results show that ‘legislation and policy’ is a better strategy, because concentrations of all compounds are reduced, while for ‘green pharmacy’ only the concentrations of pharmaceuticals decrease. From these results it is concluded that ‘legislation and policy’ is the most sustainable, applicable and cost-efficient strategy to reduce concentrations of selected compounds in surface water and drinking water in the Netherlands. With this strategy governmental regulations regarding the emission of OMPs into the water cycle are improved. Comparing the two case studies with each other it can be concluded that in a groundwater driven system the influence of OMPs seems to be less acute than in a surface water system. However, in the groundwater system the effects of the presence of OMPs will be noticeable after a longer period, which makes this system more unpredictable and it takes more time till measures are resulting in a decrease in concentrations. In this project the MCA is performed without exact numbers for the criteria ‘sustainability’, ‘applicability’ and ‘cost-efficiency’. Further research on these aspects and the addition of more criteria improves the reliability of the MCA and thus of the winning strategy. Regarding the composed models of the case studies more attention needs to be paid to the assumptions on mixing and decay. In a system with high residence times (like the groundwater system of the Bethunepolder) decay could play an important role in the modelling.