COMPARATIVE STUDY OF FIVE FILTER TYPES FOR STORMWATER TREATMENT: USING A WHOLE EFFLUENT ASSESSMENT APPROACH TO EVALUATE FILTER PERFORMANCE
(English)Manuscript (preprint) (Other academic)
The release of hazardous substances to the environment from industrial activities in Sweden is heavily restricted due to pieces of legislation such as the Industrial Emissions Directive (2010/75/EU). In the directive, the whole effluent assessment (WEA) methodology is included as a suitable approach to characterization of effluent waters. The use of WEA methods in the evaluation of treatments for complex effluent waters has great advantages when comparing to using chemical analysis of individual substances alone. In this comparative study the WEA methodology of combining toxicity testing with chemical analysis was applied to evaluate the performance, stability and safety of four stormwater filter types in comparison with the conventional filter material active carbon. The filter materials were the two sorbent filter materials pine bark and polonite; and the two combination filters pine bark/polonite (filtration through pine bark followed by filtration through polonite) and polonite/pine bark (filtration through polonite followed by filtration through pine bark). The stormwater treated in the study was sampled from two points at a metals manufacturing site in mid-Sweden. A preliminary analysis of the water showed high concentrations of heavy metals and in particular of Zn, with concentrations exceeding 36 mg/L. The stormwater pH was neutral (7.5) and suspended solids content was approximately 130 mg/l. Samples of the stormwater, corresponding to ten filter bed volumes, were filtered through a pilot-scale 250 ml filter columns with the four filters or activated carbon. The filtered water samples were analysed for Zn and pH. An aquatic ecotoxicity test battery was used to measure acute and chronic toxic effects of the untreated and treated stormwater samples. The test battery assessed luminescent bacteria acute toxicity (30-min Microtox® ISO 11348-3 using Vibrio fischeri), growth inhibition of the green unicellular algae Pseudokirchneriella subcapitata and genotoxicity with the bacterial umu assay using Salmonella typhimurium TA1535/pSK1002 (ISO 13829). The pine bark sorbent showed the highest average Zn removal efficiency of the single filter materials after activated carbon. The results from the stormwater filtration with combination materials were difficult to interpret. All filter types, except pine bark, increased pH of the treated waters > 9. Pine bark lowered the pH of the treated water below 5 even after filtration of 10 bed volumes of stormwater. Although pH of the treated waters was only adjusted for the Microtox test, there was a statistically significant positive correlation between the response of this test and the algal assay. Activated carbon showed the highest reduction of Zn contamination and toxicity of the treated waters. There was no significant correlation between the level of zinc contamination and toxic response of the treated waters. Although pine bark lowered pH significantly, in comparison to the other filter types, there was no significant correlation between the pH and the toxic response of the filtered waters.
WHOLE EFFLUENT ASSESSMENT; COLUMN FILTER; PINE BARK; POLONITE; MICROTOX; UMU
Engineering and Technology
Research subject Energy- and Environmental Engineering
IdentifiersURN: urn:nbn:se:mdh:diva-14621OAI: oai:DiVA.org:mdh-14621DiVA: diva2:527251