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In-catchment stormwater quality treatment using nature-mimicking biofilter systems

Published: 7 October 2022

During recent decades, blue-green infrastructures (BGI) have been developed to control stormwater quality and quantity. Among BGIs, biofilter technology is a nature-mimicking, engineered system that has high potential to improve stormwater quality inside the catchment. Lately, several studies to assess the performance of stormwater treatment under actual conditions are carried out by Stormwater&Sewers testing various biofilter systems across Sweden in different urban areas of Stockholm, Malmö, Sundsvall and Växjö.

In one of these projects, runoff quality monitoring and the treatment of selected organic micropollutants were addressed. The project was carried out on an approximately 4.7-ha catchment on the E4 highway bridge over the Sundsvall Bay. First, stormwater quality was analyzed based on relevant databases and water quality standards for organic micropollutants. Then the potential surrogate quality parameters that may be indicators for the organic micropollutants contamination levels in the future monitoring programs on this site were investigated. Next, a gross pollutant trap (GPT)-biofilter/sand filter treatment train built beside the catchment was studied in order to understand the removal efficiency and concentration variability of organic micropollutants in the system.

The result showed that the stormwater contains a significant (risky) amount of poly aromatic hydrocarbons (PAHs, mainly medium and heavy weight molecules), heavy petroleum hydrocarbons (PHCs), bisphenol A (BPA), suspended solids, and sometimes alkylphenols which should be treated before being discharged to water bodies. Furthermore, turbidity was discovered as a sufficient surrogate parameter for PAHs and heavier PHCs. Similarly, total organic carbon and conductivity can be substitutional indicators for BPA concentration in stormwater. Meanwhile, investigating the water quality at the outflow of the constructed treatment train revealed that sand filter and vegetated biofilter could remove 52% and >80% of organic micropollutants, respectively. In contrast, the gross pollutant trap section did not contribute to stormwater quality enhancement at all.

In summary, the study showed that stormwater sand/biofilter systems can be promising solutions for organic micropollutants removal. However, the design might still need improvement to optimally meet many kinds of micropollutants removal. Besides, the study also showed that the investigated indicator parameters potentially could be used for simplified stormwater quality monitoring which may reduce high analysis costs in the future.

 

Ali Beryani

Ali Beryani, PhD Student

Phone: +46 (0)920 492841
Organisation: Urban Water Engineering, Architecture and Water, Department of Civil, Environmental and Natural Resources Engineering