Treatment of tunnel wash waters--experiments with organic sorbent materials. Part I: Removal of polycyclic aromatic hydrocarbons and nonpolar oil

Tunnel wash water in a cold climate: characteristics, ecotoxicological risk, and effect of sedimentation

The characterization of tunnel wash water (TWW) from 12 Norwegian tunnels showed very high concentrations of total suspended solids (TSS), metals, and polycyclic aromatic hydrocarbons (PAHs). Iron (Fe), aluminum (Al), and manganese (Mn) were mainly particle-associated. They are efficiently removed by sedimentation, while the dissolved concentrations of toxic metals like Cu, Zn, and As did not change. Polycyclic aromatic hydrocarbon (PAH) concentration was higher in the dissolved than in the particulate fraction. Sedimentation treatment reduced the particulate share by about 50%. In contrast to metals, the dissolved fraction decreased by about 90% during sedimentation, most probably due to adsorption to particles that are subsequently removed during the process. The concentration levels of 8 out of 16 PAHs, Cu, Zn, and As resulted in a water quality classification of poor or very poor. Acute toxic effects could be expected after short-term exposition. After sedimentation, this was the case for only two PAHs because more harmful compounds with three to six rings were preferably removed. These may adsorb better to particles than PAHs with two rings. No change was observed for the metals. A closer evaluation of secondary treatments of TWW, including conventional technology and mobile solutions, is therefore recommended. Finally, indications for a seasonal pollution variation have been seen, mainly related to the use of salt as a de-icing agent in road maintenance.

Occurrence of traffic related trace elements and organic micropollutants in tunnel wash water

Substantially polluted tunnel wash water (TWW) is produced during road tunnel maintenance. Previous literature has reported the presence of trace elements and polycyclic aromatic hydrocarbons (PAHs). However, it was hypothesized that other organic pollutants are present, and more knowledge is needed to prevent environmental harm. This study reveals for the first time the presence of four short- and 17 long-chained per- and polyfluoroalkyl substances (PFASs), three benzothiazoles (BTHs), six benzotriazoles (BTRs), four bisphenols, and four benzophenones in TWW from a Norwegian road tunnel over a period of three years. Concentrations of PAHs, PFASs, BTHs, and BTRs were higher than previously reported in e.g., road runoff and municipal wastewater. Trace elements and PAHs were largely particulate matter associated, while PFASs, BTHs, BTRs, bisphenols, and benzophenones were predominantly dissolved. 26 of the determined contaminants were classified as persistent, mobile, and toxic (PMT) and are of special concern. It was recommended that regulations for TWW quality should be expanded to include PMT contaminants (such as PFPeA, PFBS, BTR, and 4-OH-BzP) and markers of pollution (like 2-M-BTH, 2-OH-BTH, and 2-S-BTH from tire wear particles). These findings highlight the need to treat TWW before discharge into the environment, addressing both, particulate matter associated and dissolved contaminants.

In vivo and in vitro effects of tunnel wash water and traffic related contaminants on aquatic organisms

In order to maintain the construction and safety of road tunnels, they are routinely washed. The wash water appears to be highly polluted with a plethora of contaminants in elevated concentrations. In addition, new and emerging compounds are likely to occur. The discharge water has shown acute toxic and sub-lethal effects in several organisms. In this study, ecotoxicity tests with algae (Pseudokirchneriella subcapitata) and in vitro tests with primary rainbow trout (Oncorhynchus mykiss) hepatocytes were used to characterize the effect of TWW from three different tunnels. In addition, selected N- and Cl-PAHs were tested for cytotoxicity, EROD activity and CYP1A protein production. TWW samples and/or extracts from two tunnels reduced the algal growth and induced cytotoxicity, EROD activity and CYP1A protein production in vitro. Four of the eight tested Cl- and N-substituted PAHs induced EROD activity and CYP1A protein production at micro-molar concentrations. N-PAHs were detected in samples from the tunnel wash, highlighting substituted PAHs as potentially important traffic-related contaminants.

Exposure of brown trout (Salmo trutta L.) to tunnel wash water runoff--chemical characterisation and biological impact

Washing and cleaning of road tunnels are a routinely performed maintenance task, which generate significant amount of polluted wash-water runoff that normally is discharged to the nearest recipient. The present study was designed to quantify chemical contaminants (trace metals, hydrocarbons, PAH and detergents) in such wash water and assess the short term impact on brown trout (Salmo trutta L.) based on in situ experiments. Selected endpoints were accumulation of trace metals in gills, haematological variables and hepatic mRNA transcription of five biomarkers reflecting defence against free radicals, trace metals, planar aromatic hydrocarbons and endocrine disruptions which were measured prior (-3h), during (1 and 3h) and after the tunnel wash (14, 38 and 86h). Our findings showed that the runoff water was highly polluted, but most of the contaminants were associated with particles which are normally considered biologically inert. In addition, high concentrations of calcium and dissolved organic carbon were identified in the wash water, thus reducing metal toxicity. However, compared to the control fish, a rapid accumulation of trace metals in gills was observed. This was immediately followed by a modest change in blood ions and glucose in exposed fish shortly after the exposure start. However, after 38-86h post wash, gill metal concentrations, plasma ions and glucose levels recovered back to control levels. In contrast, the mRNA transcription of the CYP1A and the oxidative stress related biomarkers TRX and GCS did not increase until 14h after the exposure start and this increase was still apparent when the experiment was terminated 86h after the beginning of the tunnel wash. The triggering of the defence systems seemed to have successfully restored homeostasis of the physiological variables measured, but the fish still used energy for detoxification four days after the episode, measured as increased biomarker synthesis.