Highlights of the Environmental Technologies Sessions at the 2010 SETAC Europe Annual Meeting
Joop Harmsen, Center for Water and Climate, Alterra-Wageningen University and Research Center, The Netherlands
The SETAC community does not typically focus on technology; rather, members are driven by knowledge development in ecotoxicology, environmental chemistry and risk assessment. Seville 2010 was the first time that several sessions were devoted to environmental technologies. Technology-related presentations and posters were also noticeable as part of other sessions. This is a natural and important step toward achieving SETAC’s mission of supporting the development of principles and practices for protecting, enhancing and managing sustainable environmental quality and ecosystem integrity.
Environmental technologies to clean up contaminated water, soils and sediments have been available for a long time. They can be successful, but they can also be too expensive for use. The presence of post-treatment residuals is often a drawback. Unfortunately, some remediation methods for soil and sediment have to be considered fairy tales.
Environmental remedial technologies, especially those for soil and sediment remediation are moving from contaminant removal to reduction of risks, taking into account the concept of bioavailability. This can be considered a challenge for SETAC in developing the methods for the future.
Presence of residual medicine in water is an important issue and these compounds could be removed from wastewater streams. Removal of 17α –ethinylestradiol in effluent with a nitrifier-enriched culture was shown to be very effective (De Gusseme et al.) and this possibility was confirmed by Lawton et al., who measured better removal from advanced tertiary treatments in the UK. Carbon nanomaterials may also play a role in medicine removal (Farré et al.). Microporous titansilicate (Lopes et al.) and olive waste (Ángelis Martin-Lara) can be used for removal of heavy metals and plants can be used for uranium (Favas et al.).
The risks of heavy metals in groundwater can be reduced by stimulation of in situ precipitation as sulfide (Muquet et al.). Treatment of groundwater contaminated with volatile chlorinated solvents has been successfully conducted at several sites based on biological stimulation to reduce these compounds (Lakhwala et al). Trees have also been shown to take up the contaminated groundwater and become increasingly effective as they age (Klein et al.); however, a disadvantage of using trees is the evapotranspiration of the chlorinated solvents by the leaves. Biodegradation in the trees and root systems becomes more effective by introduction of endophytic bacteria in the root zone (Weyens et al.). The environment in a constructed wetland can also stimulate biodegradation of perchloroethene and chlorobenzenes. However, an adaptation time of two years was necessary (Braeckevelt et al), indicating that more knowledge is needed before natural wetlands can be used for remediation of these compounds.
Organic contaminants strongly adsorb to activated carbon and this process was shown to effectively reduce bioavailability. This reduction also results in s a reduction of the biodegradation rate. Stimulation of the biodegradation rate is also possible if toxicity for degrading organisms is reduced by activated carbon (Vasilyeva et al). An important finding was that adding activated carbon to sediment had no negative effect on tested organisms (Kupryiachyk et al).
Charcoal has adsorbing properties and is widely available, including remote areas in African countries (Harmsen et al.). While application will reduce the availability of most contaminants, the presence of PAHs in charcoal (Freddo et al) may lead to persistence of atrazine (Jablonowski et al). Use of charcoal should take this into account; risks are only reduced if advantages are larger than disadvantages.
Phytoextraction is often considered as a technology to remove heavy metals. This is only effective if vegetation is very efficient in uptake. Increase in availability by using chelating agents could be helpful, but if this leads to toxicity it is counterproductive (e.g., EDTA by Gatti et al. and Rhamnolipid by Wen et al.). An important consideration in phytoextraction is the beneficial use of the vegetation produced as part of the process. An example was presented regarding the manufacture of paper from banana stems and production of flowers, both grown on an arsenic contaminated site in Thailand (Persian et al.).
Phytostabilization seems to be more promising, especially in mining areas. Reforestation can stabilize soils and reduce leaching due to evaporation of rainfall; however, the toxicity of soil must be decreased and fertility increased for reforestation to be successful. Numerous materials are used to reduce toxicant bioavailability and fertilize the soil: marble cutting sludge, organic matter, iron, poultry and sheep manure, cow and pig slurry, paper mill sludge, compost, sewage sludge, gypsum, waste, calcite, bone meal and biochar. The effectiveness of amendments in reducing toxicity is different for different heavy metals; amendments themselves can be toxic and regional differences may be observed. Proper vegetation has to be selected and excluders of heavy metals are recommended. Uptake by leaves may recontaminate the leaf litter layer so species with low accumulation in the leaves should be selected (Van Nevel et al.). Oliva et al. spoke of selecting indigenous and rapidly growing plants to stabilize a site. Pradas et al. and Lonardo et al. spoke about the importance of selecting the right genotype to improve phytostabilization performance. Mycorrhizal inoculation may also reduce uptake. If the contamination is limited to one contaminant an excluder can be easily selected (e.g., an excluder for arsenic by Manzano et al.), but if more contaminants are involved, selection may result in a compromise.
In phytostabilization, it is the right combination of amendment, vegetation and site management—not contaminant removal—that reduces risks. Given the different properties of different contaminants, there will not be a general solution. Any solution will be site specific and should be based on proven knowledge, and decisions should be based on the expected net environmental benefit.
The first large pilots on capping of sediment at a depth of 30-100m in a Norwegian fjord (Amstaeter et al.) and on a DDT contaminated site in Pakistan (Younas et al) were presented. A more technology-based stabilization approach was presented by van de Velde et al. They used geo-polymerization to change dredged sediment into a building material that can be used for flood protection and road construction.
New technologies that were presented included electro-reclamation of heavy metals and electro-stimulation of biodegradation (lab scale only). Nanoparticles are already used for water treatment but they may be toxic. This should be taken into account if these particles are proposed for use in groundwater treatment and soil and sediment remediation.
Environmental technologies make it possible to remove contaminants, and more importantly, reduce risks. Advancing the use of environmental technologies to reduce risk, even in the absence of mass removal, is a suitable challenge for the SETAC community with its expertise in environmental chemistry, ecotoxicology, risk assessment and life cycle analysis. To quote soccer player, coach and analyst Johan Cruijff, “every disadvantage has its advantage.”
The Seville environmental technology presentations mostly focused on European or North-American conditions. SETAC wants to become global. In Seville there was already a session on ecotoxicology in the tropics and a few presentations on remediation in tropical countries. It is a challenge for SETAC to promote transfer of knowledge to the tropics. This can be difficult due to lack of facilities or other logistic constraints. This should not hamper attempts to apply environmental technologies in the tropics. Common sense has to prevail. Often problems seem too difficult to solve because technologies are too expensive or too difficult to export. Dedicated commitment of creativity and expertise will be necessary to break this cycle and really reduce risks for people living on or around contaminated sites.
SedNet, 2007. Sustainable Management of Sediment Resources. Sediment and dredged material Treatment. Eds: Bortone G. and L. Palumbo. Elsevier, Amsterdam.
All other references refer to the presentations as summarized in the abstract book or extended abstracts of Seville2010
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