Hazardous substances

• Directives, legislation, regulations, prohibitions, standards.
• At different levels – EU, national, regional level – prohibition, standard

• Special taxes and fees for industries/enterprises, environmental costs, Waste water fees

Source Control

• Product design/redesign – awareness of hazardous substances, substitution of hazardous substances with less harmful ones, using eco-packages, eco-labelling
• Waste management – sorting of wastes, recycling
• Water treatment – pre-treatment of wastewater for industrial processes, pre-treatment of storm waters

End-of-pipe measures – technical measures to avoid emissions/loads from reaching environment

• Treatment of urban wastewater
• Advances in wastewater treatment – implementation of ozonation, adsorption (e.g. activated carbon), membrane filtration technologies
• Sewage sludge treatment – controlled incineration, avoid land application of sewage sludge if it is contaminated, safe landfilling etc.

• Eco-labelling
• Company’s environmental values – commitment towards a better future for our planet.

• Precipitation

Chemical precipitation means that metals, mainly in the form of metallic ions in wastewater, form insoluble particles and flocs which can be removed by sedimentation or filtration. The precipitation is normally achieved by firstly adjusting the pH and secondly adding iron or aluminium salt to form chemical flocs. The settled flocs are called sludge and must be further treated.

Examples of substances or groups of substances that can be removed by chemical precipitation are metals and heavy metals, bulk organic substances, and phosphorous substances.

• Ozonation

In an ozonation treatment step, reactive ozone gas is fed into the wastewater to oxidize organic substances. Ozone is unstable and is produced on site at the treatment facility. The water retention time in the ozone contact tanks is in the range of 10 to 30 minutes. Normally, a sand filter or equivalent is installed after the ozonation step to enable the establishment of biofilm on the sand grains, which can handle the produced easily degradable organic substances and potential by-products from the ozonation.

Ozone in a sufficient quantity and under the right conditions is able to oxidize many organic compounds including pharmaceuticals and some pesticides. However, the oxidization might be only partial or otherwise incomplete and sometimes the oxidization products might be even more harmful than the initial compound.

• Activated carbon

Adsorption with activated carbon (AC) is a widespread technology to remove many different organic substances from different fluids. The porous high adsorptive surface of activated carbon varies in the range of 500-1500 m2/g. AC is produced from a variety of raw materials such as coal, wood or coconut shells. Two main forms of activated carbon are used in water and wastewater treatment: powdered activated carbon (PAC) or granular activated carbon (GAC). GAC has a larger particle diameter, 0.2 to 5 mm compared to PAC with particle diameters typically 0.015–0.025 mm.

Treatment with GAC is normally performed in fixed bed filters. After several thousand passed bed volumes of water and adsorbed organic substances, the GAC grains must be regenerated.

PAC treatment consists of an initial mixing tank for wastewater and PAC, contact tanks, a separation unit e.g. sedimentation tank, and sand filter or ultrafilter. The spent PAC is discharged to sludge handling or to a separate PAC handling for later incineration. The used PAC is not reactivated.

Examples of substances or groups of substances that can be removed by activated carbon are pharmaceuticals and PFAAs, including PFOS and biocides.

• Nanofiltration
• Ultrafiltration

Membrane filtration is a process where particles or solutes are being separated with a semi-permeable membrane and water pressure is used as the driving force. Nanofiltration (NF) and reverse osmosis (RO) are potential separation applications for removal of hazardous substances from wastewater. The membrane treated wastewater leaves as permeate while most of the organic substances and some salts are concentrated in the retentate from the membrane units. RO and NF produce large volumes of retentates, at a realistic operation level even 5 %. Usually, this retentate must be further treated.

The membranes are frequently cleaned by using either alkaline or acid water solutions, or both. Compared to ozonation, the energy consumption mainly for the pumps in the membrane filtration is estimated to be 2 and 3 times higher for NF and RO, respectively.

Examples of substances or groups of substances that can be removed by membrane filtration are pharmaceuticals and PFAAs, including PFOS.

Business register was used to search for companies located in the pilot watershed.

Companies with a field of operation that could be viewed as a potential source of hazardous substances were added to the list of potential hotspots: construction; chemistry; logging; electronics; waste; agriculture; transportation; metal industry; glass industry; food industry; textile industry; hospitals and other social welfare services; production and repair of machines and components.

Credit info was used to determine whether the company is active and to check its operating address.

Information about environmental permits and wastewater outlets was also added.

Orthophotos were used to estimate the size of the company and whether any materials were stored outside.

Example: Mapping of Estonian WaterChain pilot area

Passive sampling is a new method in the areas of monitoring for determination of organic pollutant concentration levels in water bodies. Passive sampling is suitable for monitoring priority hazardous compounds in aquatic environment unlike conventional spot sampling which does not allow long-term conclusion of the content of hazardous substances in the aquatic environment. The advantage of passive sampling over spot sampling is the possibility of estimating the time-weighted average concentrations of target pollutants in a fluctuating aquatic environment in order to obtain an adequate representative picture of the water quality and make an assessment of pollutant trends in water bodies.

The passive sampling method combines sampling and the enrichment of the compounds of concern. It is non-mechanical device capable of accumulating contaminants dissolved in the water.

Derived concentrations obtained by passive sampler represent an average contaminant concentration over a certain time period. The accumulation of substance in the sampler takes place until thermodynamic equilibrium established between the sampler and the water, or until the sampling process is interrupted.

Two types of passive samplers can be distinguished: partition passive samplers (p-PSD) and adsorption passive samplers (a-PSD). In the project’s study (pilot area with 3 sampling sites, 3 samplings for 2-4 weeks), an integrative passive sampler (Chemcatcher) was used to estimate time-weighted average concentration (TWAC) of hazardous organic compounds in surface water in the pilot area. Material that was applied during p-PSD method development was silicone rubber (SR).

Partition passive samplers (p-PSD) – hydrophobic substances with low solubility in water are strongly accumulated in p-PSDs. Method material allows the quantification of freely dissolved organic pollutants.

Adsorbtion passive samplers (a-PSD) – accumulation in the binding material is by an adsorbtion process and not by dissolution. Adsorbtion of strongly hydrophilic substances is possible.