Examples of Implementation

An example compliance assessment exercise with the nickel EQSbioavailable for waters of contrasting physicochemical properties is shown in Figure 4Figure 4a shows monitoring data for 1779 samples from 76 rivers in Austria6 were assessed using the tiered approach. Only 3 percent of samples passed to Tier 3 for consideration of local issues. Waters in Austria have previously been identified as sensitive to nickel exposures due to relatively low DOC, high pH, and low hardness. Figure 4b shows 3942 samples for 49 waterbodies in Sweden (provided by the Swedish Chemicals Agency) were assessed. At Tier 1 less than 1 percent of the samples exceed the EQSbioavailable. None of the sites exceeded the EQS when nickel bioavailability was taken into account at Tier 2. Many Swedish waters have relatively high levels of DOC as well as low hardness and pH, and these conditions represent low bioavailability to nickel.  

Figure 4: Examples of an indicative compliance assessment of
Austrian (a) (starting value of 1779) and
Swedish (b) (starting value of 3942) nickel monitoring data

 

                          a) Austria

 

                          b)  Sweden

Permits and consents for discharges into rivers are often set in order to control the overall inputs of potentially toxic substances over whole river basins or catchments. Water treatment plants that discharge effluents to surface waters will all have consented discharges. An industry discharge that goes to sewer will be regulated by the same processes, i.e., the water company will need to ensure any changes to its main permitted discharge is met through regulating the input from industry to their treatment plant. The specific approaches taken will vary locally from one country to another, although there are some general principles likely to be relatively consistent between them and all will likely use an EQS to set the limit.

For example, to set a discharge consent for a nickel containing effluent into a river with a pH of 7.3, an average DOC concentration of 3.9 mg/L, and an average Ca concentration of 8 mg/L the following process could be followed. The site specific EQSdissolved for this site is ≈ 11 µg/L dissolved Ni, and the BioF value for conversion of dissolved nickel concentrations to bioavailable nickel concentrations is 0.37. If one tenth of the EQS is permitted in the receiving water per discharge then the maximum acceptable concentration of nickel in the receiving water from this discharge is 1.1 µg/L dissolved nickel.

Therefore, the permissible concentration in the discharge can be calculated from the effluent flow and the flow of the river, in combination with the permissible contribution of nickel in the river from this discharge. If the effluent discharge from the site is 2886 m3/d, and the flow of the receiving water 12,441,600 m3/d then the permissible concentration of nickel in the discharge can be calculated as:

  Cdischarge x Vdischarge = Creceiving water x (Vreceiving water + Vdischarge)  

Where Cdischarge is the permissible concentration in the discharge (mg/L), Vdischarge is the volumetric flow rate of the discharge (m3/d), Creceiving water is the permitted nickel concentration in the receiving water from this discharge (mg/L), and Vreceiving water is the volumetric flow rate of the receiving water (m3/d). 

Although the concentration in the discharge calculated in this manner is a dissolved concentration the permitted concentration in the discharge may, in some cases, be expressed as a total nickel concentration.

 

http://wisa.lebensministerium.at/ (last accessed January 2014)