Water quality guidelines for chemicals: learning lessons to deliver meaningful environmental metrics

Many jurisdictions around the globe have well-developed regulatory frameworks for the derivation and implementation of water quality guidelines (WQGs) or their equivalent (e.g. environmental quality standards, criteria, objectives or limits). However, a great many more still do not have such frameworks and are looking to introduce practical methods to manage chemical exposures in aquatic ecosystems. There is a potential opportunity for learning and sharing of data and information between experts from different jurisdictions in order to deliver efficient and effective methods to manage potential aquatic risks, including the considerable reduction in the need for aquatic toxicity testing and the rapid identification of common challenges. This paper reports the outputs of an international workshop with representatives from 14 countries held in Hong Kong in December 2011. The aim of the workshop and this paper was to identify ‘good practice’ in the development of WQGs to deliver to a range of environmental management goals. However, it is important to broaden this consideration to cover often overlooked facets of implementable WQGs, such as demonstrable field validation (i.e. does the WQG protect what it is supposed to?), fit for purpose of monitoring frameworks (often an on-going cost) and finally how are these monitoring data used to support management decisions in a manner that is transparent and understandable to stakeholders. It is clear that regulators and the regulated community have numerous pressures and constraints on their resources. Therefore, the final section of this paper addresses potential areas of collaboration and harmonisation. Such approaches could deliver a consistent foundation from which to assess potential chemical aquatic risks, including, for example, the adoption of bioavailability-based approaches for metals, whilst reducing administrative and technical burdens in jurisdictions.     

Evaluation of surface water quality using an ecotoxicological approach: a case study of the Alqueva Reservoir (Portugal)

Background, aim, and scope  

Freshwater reservoirs can be impacted by several hazardous substances through inputs from agricultural activity, sewage discharges, and groundwater leaching and runoff. The water quality assessment is very important for implementation of the monitoring and remediation programs to minimize the risk promoted by hazardous substances in aquatic ecosystems. Evaluation of the degree of contamination of aquatic environments must not take in account only its chemical characterization but it must be complemented with biological assays, which determine potential toxic effects and allows an integrated evaluation of its effects in populations and aquatic ecosystem communities. The application of this type of strategy has clear advantages allowing a general evaluation of the effects from all the water components, including those due to unknown substances and synergic, antagonistic, or additive effects. There are only a few studies that reported ecotoxicological acute end points, for the assessment of surface water quality, and the relationship among toxicity results and the anthropogenic pollution sources and the seasonal period. The aim of this study was to assess the ecotoxicological characterization of the surface water from Alqueva reservoir (South of Portugal) and to evaluate the influence of anthropogenic sources of pollution and their seasonal variation in its toxicity. The construction of Alqueva reservoir was recently finished (2002) and, to our knowledge, an ecotoxicological assessment of its surface water has not been performed. Because of that, no information is available on the possible impact of pollutants on the biota. The surface water toxicity was assessed using acute and chronic bioassays. The results are to be used for developing a monitoring program, including biological methods.     

The evaluation of the equilibrium partitioning method using sensitivity distributions of species in water and soil

The equilibrium partitioning method (EqP-method) can be used to calculate soil quality standards (expressed in mg/kg) from aquatic quality standards (expressed in microg/l) using a partitioning coefficient. The validity of this application of the EqP-method was studied comparing aquatic with terrestrial toxicity data. The data set collected for deriving environmental quality standards in the Netherlands, was used for this study. For 10 organic substances (chlorpyrifos, atrazine, carbofuran, pentachlorophenol, chlordane, aldrin, trichlorobenzene, heptachlor, trichlorophenol and trichloroethene) and for 8 metals, sufficient data were available. The aquatic toxicity data were multiplied by the partitioning coefficient in order to obtain aquatic data expressed in mg/kg. For some compounds the terrestrial toxicity data were significantly higher than the aquatic data but for other compounds it was the other way around. These differences indicate that the EqP-method can give significant over-or underestimations, due to inaccurate partitioning coefficients or differences in species sensitivities. These over- or underestimations can have an impact on the setting of environmental quality standards which are based on the hazardous concentration 5% (HC5) values. The uncertainty in the calculation of HC5 values attributed to the use of the EqP-method, was quantified. The HC5 values derived using the EqP-method were in 5% of the cases more than 20 times higher than the corresponding HC5 values that were derived directly from soil toxicity tests. Despite of this uncertainty the use of the EqP-method can still be advocated for setting soil quality guidelines when only a very limited number of terrestrial toxicity data are available.     

Potential impacts of water injection dredging on water quality and ecotoxicity in Limehouse Basin, River Thames, SE England, UK

The use of water injection dredging (WID) is increasing in the UK's inland waterways and marinas. Jets of water are injected under low pressure directly into bottom sediment creating a turbulent water-sediment mixture that flows under the influence of gravity. Many of these sediments are highly contaminated and little is known of the effects of contaminant release on water quality or the risk to biota living in both the sediment and the water column. Sediment cores were collected from Limehouse Basin, a proposed WID site in SE England and current sediment toxicity was assessed using a number of techniques. Comparison of metal data to US sediment quality guidelines indicated intermediate levels of toxicity while, calculation of acid volatile sulphide to simultaneously extracted metal ratios underestimated the potential toxicity to sediment dwelling organisms. In contrast, porewater ammonia concentrations were in excess of all published ecotoxicological guidelines and indicate serious risk to biota. Re-suspension experiments were used to mimic the effects of WID on overlying water quality and ecotoxicity tests were carried out on elutriates using Daphnia magna to examine the impacts on biota. Concentrations of a range of metals in the elutriates predict that adverse biological effects would be observed during WID, however only 10% of the elutriate samples caused an adverse effect on Daphnia. Limehouse Basin is a complex aquatic environment receiving predominantly fresh waters while the sediments have high porewater chloride concentrations reminiscent of previous tidal inputs to the basin, making the choice of test organism problematic.     

Accounting for both local aquatic community composition and bioavailability in setting site-specific quality standards for zinc

Recent years have seen considerable improvement in water quality standards (QS) for metals by taking account of the effect of local water chemistry conditions on their bioavailability. We describe preliminary efforts to further refine water quality standards, by taking account of the composition of the local ecological community (the ultimate protection objective) in addition to bioavailability. Relevance of QS to the local ecological community is critical as it is important to minimise instances where quality classification using QS does not reconcile with a quality classification based on an assessment of the composition of the local ecology (e.g. using benthic macroinvertebrate quality assessment metrics such as River InVertebrate Prediction and Classification System (RIVPACS)), particularly where ecology is assessed to be at good or better status, whilst chemical quality is determined to be failing relevant standards. The alternative approach outlined here describes a method to derive a site-specific species sensitivity distribution (SSD) based on the ecological community which is expected to be present at the site in the absence of anthropogenic pressures (reference conditions). The method combines a conventional laboratory ecotoxicity dataset normalised for bioavailability with field measurements of the response of benthic macroinvertebrate abundance to chemical exposure. Site-specific QS_ref are then derived from the 5%ile of this SSD. Using this method, site QS_ref have been derived for zinc in an area impacted by historic mining activities. Application of QS_ref can result in greater agreement between chemical and ecological metrics of environmental quality compared with the use of either conventional (QS_con) or bioavailability-based QS (QS_bio). In addition to zinc, the approach is likely to be applicable to other metals and possibly other types of chemical stressors (e.g. pesticides). However, the methodology for deriving site-specific targets requires additional development and validation before they can be robustly applied during surface water classification.     

Is the evaluation of “traditional” physicochemical parameters sufficient to explain the potential toxicity of the treated wastewater at sewage treatment plants?

Water scarcity is one of the most important environmental and public health problems of our century. Treated wastewater reuse seems to be the most attractive option for the enhancement of water resources. However, the lack of uniform guidelines at European and/or Mediterranean level leaves room for application of varying guidelines and regulations, usually not based on risk assessment towards humans and the environment. The benefits of complementing the physicochemical evaluation of wastewater with a biological one are demonstrated in the present study using Cyprus, a country with extended water reuse applications, as an example. Four organisms from different trophic levels were used for the biological assessment of the wastewater, namely, Pseudokirchneriella subcapitata, Daphnia magna, Artemia salina and Vibrio fischeri. The physicochemical assessment of wastewater based on “traditional” chemical parameters indicated that the quality of the wastewater complies with the limits set by the relevant national guidelines for disposal. The ecotoxicological assessment, however, indicated the presence of toxicity throughout the sampling periods and most importantly an increase of the toxicity of the treated wastewater during summer compared to winter. The resulting poor correlation between the physicochemical and biological assessments demonstrates that the two assessments are necessary and should be performed in parallel in order to be able to obtain concrete results on the overall quality of the treated effluent. Moreover, a hazard classification scheme for wastewater is proposed, which can enable the comparison of the data sets of the various parameters deriving from the biological assessment in a comprehensive way.     

Impacts of lawn-care pesticides on aquatic ecosystems in relation to property value

To determine the potential impacts of lawn-care pesticides on aquatic ecosystems, the macroinvertebrate communities of six streams were assessed using a multimetric approach. Four streams flowed through residential neighborhoods of Peachtree City, GA, USA, with differing mean property values and two reference streams were outside the city limits. A series of correlation analyses were conducted comparing stream rank from water quality and physical stream parameters, habitat assessments, benthic macroinvertebrate metric, pesticide toxicity and metal toxicity data to determine relationships among these parameters. Significant correlations were detected between individual analyses of stream rank for pesticide toxicity, specific conductance, turbidity, temperature and dissolved oxygen with benthic macroinvertebrate metrics.     

Derivation of ambient water quality criteria for formaldehyde.

This paper describes the derivation of aquatic life water quality criteria for formaldehyde, developed in accordance with United States Environmental Protection Agency's (USEPA's) Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses. The initial step in deriving water quality criteria was to conduct an extensive literature search to assemble available acute and chronic toxicity data for formaldehyde. The literature search identified a large amount of information on acute toxicity of formaldehyde to fish and aquatic invertebrates. These acute data were evaluated with respect to data quality, and poor quality or uncertain data were excluded from the data base. The resulting data base met the USEPA requirements for criteria derivation by having data for at least one species in at least eight different taxonomic families. One shortcoming of the literature-derived data base, however, was that few studies involved analytical confirmation of nominal formaldehyde concentrations and reported toxicity endpoints. Also, there were relatively few data on chronic toxicity. The acute toxicity data set consisted of data for 12 species of fish, 3 species of amphibians, and 11 species of invertebrates. These data were sufficient, according to USEPA guidelines, to calculate a final acute value (FAV) of 9.15 mg/l, and an acute aquatic life water quality criterion (one-half the FAV) of 4.58 mg/l. A final acute-chronic ratio (ACR) was calculated using available chronic toxicity data and USEPA-recommended conservative default assumptions to account for missing data. Using the FAV and the final ACR (5.69), the final chronic aquatic life water quality criterion was determined to be 1.61 mg/l.     

Application of biological safety index in two Japanese watersheds using a bioassay battery

In order to integratedly evaluate the biological safety as a water quality index, an assessment method based on three toxicity tests (algae growth inhibition, daphnia immobilization and larval fish toxicity) was developed. In this study, the developed method was used to screen, evaluate and rank the biological safety of small rivers near agricultural, industrial and residential areas. Twenty-seven representative water samples were collected from the Kaname River watershed and the Hinata River watershed in Kanagawa Prefecture, Japan. The results indicated that (1) the biological safety of water from the Hinata River ranked much higher than those from the Suzu River and the Shibuta River due to less human activities, (2) the biological safety from outlets of paddy fields ranked much worse than those from point source discharges of toxic pollutants, (3) the use of pesticides significantly affected the water quality of nearby small rivers and ditches during the pesticide application season, (4) the effects of different kinds of pesticides could successfully be classified using one toxicity test component of the bioassay battery, and (5) there was no significant quantitative relationship between the toxicity and dissolved organic carbon (DOC) for the studied water samples. The toxicities of water samples in this study were in agreement with the concentrations of pesticides determined with chemical methods by other researchers, which demonstrated that the developed assessment method was reliable to screen site contaminated with organic chemicals for priority management.     

Comparison of species sensitivity distributions for species from China and the USA

China has recently commenced water quality criteria (WQC) research using the species sensitivity distribution (SSD) method; however, it is difficult to obtain sufficient native species toxicity data for thousands of contaminants. In this study, the feasibility of using non-native toxicity data in deriving native WQC was analyzed. We constructed SSDs based on acute toxicity data of species from China and the USA for eight priority pollutants, and compared the sensitivities of different taxonomic groups between the two countries. The results showed that the SSD method of log-logistic distribution fit the toxicity data of different taxa well. The comparison of sensitivity distribution and hazardous concentration for 5 % of the species and 50 % of the species showed that there was no significant difference between Chinese and American taxa. It could be feasible to use toxicity data from the USA to provide a temporary way to protect organisms in China in emergency situations or for management of priority pollutants when native toxicity data are lacking.     

Derivation of site-specific surface water quality criteria for the protection of aquatic ecosystems near a Korean military training facility

This study suggested the first Korean site-specific ecological surface water quality criteria for the protection of ecosystems near an artillery range at a Korean military training facility. Surface water quality (SWQ) criteria in Korea address human health protection but do not encompass ecological criteria such as limits for metals and explosives. The first objective of this study was to derive site-specific SWQ criteria for the protection of aquatic ecosystems in Hantan River, Korea. The second objective was to establish discharge criteria for the artillery range to protect the aquatic ecosystems of Hantan River. In this study, we first identified aquatic organisms living in the Hantan River, including fishes, reptiles, invertebrates, phytoplankton, zooplankton, and amphibians. Second, we collected ecotoxicity data for these aquatic organisms and constructed an ecotoxicity database for Cd, Cu, Zn, TNT, and RDX. This study determined the ecological maximum permissible concentrations for metals and explosives based on the ecotoxicity database and suggested ecological surface water quality criteria for the Hantan River by considering analytical detection limits. Discharge limit criteria for the shooting range were determined based on the ecological surface water quality criteria suggested for Hantan River with further consideration of the dilution of the contaminants discharged into the river.     

The health effects and ecological significance of chlorine residuals in water

During the past several years, chlorine residuals and chlorinated organic compounds in drinking waters and aquatic environments have become a significant topic of study for scientists concerned about the quality of life in aquatic ecosystems as well as general public health. The effects of direct toxicity and/or carcinogenicity to human and aquatic life are the focal points for this concern.The effects of chloramines and chlorinated organic compounds present in the water distribution system after chlorination treatments are reviewed. Also discussed are the effects of chlorinated discharges from municipal secondary treatment plants and power plants on human health and aquatic life. The toxic significance of environmental chemicals are described.     

Geno-toxicity assay of sediment and water samples from the Upper Silesia post-mining areas, Poland by means of Allium-test

Genotoxic potential of two environmental compartments (water and sediment) from the Upper Silesia Coal Basin (USCB), Poland were evaluated and compared by employing root meristem cells of Allium cepa. The clear genotoxic effect of water and sediment sampled was shown, with an important contribution of severe types of cytogenetic abnormalities. The most biologically relevant pollutants were revealed through multivariate statistical analysis of relationships between biological effects registered and the environment contamination. Overall, results of simultaneous use of conventional monitoring methods and biological tests suggested that contemporary levels of persistent pollutants in post-mining areas of the USCB may enhance the risk both for human health and biological components of natural ecosystems.     

Haloacetic acids in the aquatic environment. Part II: ecological risk assessment

Haloacetic acids (HAAs) are environmental contaminants found in aquatic ecosystems throughout the world as a result of both anthropogenic and natural production. The ecological risk posed by these compounds to organisms in freshwater environments, with a specific focus on aquatic macrophytes, was characterized. The plants evaluated were Lemna gibba, Myriophyllum spicatum and M. sibiricum and the HAAs screened were monochloroacetic acid (MCA), dichloroacetic acid (DCA), trichloroacetic acid (TCA), trifluoroacetic acid (TFA) and chlorodifluoroacetic acid (CDFA). Laboratory toxicity data formed the basis of the risk assessment, but field studies were also utilized. The estimated risk was calculated using hazard quotients (HQ), as well as effect measure distributions (EMD) in a modified probabilistic ecological risk assessment. EMDs were used to estimate HAA thresholds of toxicity for use in HQ assessments. This threshold was found to be a more sensitive measure of low toxicity than the no observed effect concentrations (NOEC) or the effective concentration (EC10). Using both deterministic and probabilistic methods, it was found that HAAs do not pose a significant risk to freshwater macrophytes at current environmental concentrations in Canada, Europe or Africa for both single compound and mixture exposures. Still, HAAs are generally found as mixtures and their potential interactions are not fully understood, rendering this phase of the assessment uncertain and justifying further effects characterization. TCA in some environments poses a slight risk to phytoplankton and future concentrations of TFA and CDFA are likely to increase due to their recalcitrant nature, warranting continued environmental surveillance of HAAs.     

Sediment quality guidelines: challenges and opportunities for improving sediment management

During the International Conference on Deriving Environmental Quality Standards for the Protection of Aquatic Ecosystems held in Hong Kong in December 2011, an expert group, comprising scientists, government officials, and consultants from four continents, was formed to discuss the important scientific and regulatory challenges with developing sediment quality guidelines (SQGs). We identified the problems associated with SQG development and made a series of recommendations to ensure that the methods being applied were scientifically defensible and internationally applicable. This document summarizes the key findings from the expert group. To enable evaluation of current SQG derivation and application systems, a feedback mechanism is required to communicate confounding factors and effects in differing environments, while field validation is necessary to gauge the effectiveness of SQG values in sediment quality assessments. International collaboration is instrumental to knowledge exchange and method advancement, as well as promotion of ‘best practices’. Since the paucity of sediment toxicity data poses the largest obstacle to improving current SQGs and deriving new SQGs, a standardized international database should be established as an information resource for sediment toxicity testing and monitoring data. We also identify several areas of scientific research that are needed to improve sediment quality assessment, including determining the importance of dietary exposure in sediment toxicity, mixture toxicity studies, toxicity screening of emerging chemicals, how climate change influence sediments and its biota, and possible use of new toxicity study approaches such as high throughput omic-based toxicity screenings.     

Inventory of marine biotest methods for the evaluation of dredged material and sediments

An inventory of marine biotest methods for the evaluation of dredged material and sediments was compiled on behalf of the Federal Environmental Agency of Germany. Relevant assays were identified from the literature and experts from several countries contributed to a questionnaire survey on established and developing procedures. The biotest methods are applicable to whole sediment, sediment suspension, sediment elutriate, porewater and/or sediment extract. The endpoints cover acute and long-term toxicity, bioaccumulation, endocrine effects, toxic effects on reproduction, carcinogenicity and mutagenicity. Comparative analyses and evaluation of the biotest methods were conducted with regard to their sensitivity, specificity, applicability (regional specificity, availability and suitability of the test organisms), variability (physicochemical factors, natural factors and factors related to sampling and testing), cost-effectiveness, aspects of animal ethics, standardization (guidelines, intercalibration) and application for monitoring purposes in the areas of the OSPAR and Helsinki Conventions. The available information was integrated to rate the validity of the methods, their relevance for assessing impacts on ecosystems and the suitability of the methods for the evaluation of marine sediments and dredged material. Based on the rating of the individual bioassays, a tiered testing is suggested in a hierarchical approach representing a variety in taxa, biological processes and exposure routes, thereby covering the cellular, species, population and community level with a wide discriminatory and sensitivity range. The toxicological significance and complexity increases with the tiers: (1) screening and detection of impacts, (2) characterization of toxic effects, (3) verification of in situ alterations.     

Comparison of bioassays by testing whole soil and their water extract from contaminated sites

The harmful effects of contaminants on the ecosystems and humans are characterised by their environmental toxicity. The aim of this study was to assess applicability and reliability of several environmental toxicity tests, comparing the result of the whole soils and their water extracts. In the study real contaminated soils were applied from three different inherited contaminated sites of organic and inorganic pollutants. The measured endpoints were the bioluminescence inhibition of Vibrio fischeri (bacterium), the dehydrogenase activity inhibition of Azomonas agilis (bacterium), the reproduction inhibition of Tetrahymena pyriformis (protozoon), and Panagrellus redivivus (nematode), the mortality of Folsomia candida (springtail), the root and shoot elongation inhibition of Sinapis alba (plant: white mustard) and the nitrification activity inhibition of an uncontaminated garden soil used as "test organism". Besides the standardised or widely used methods some new, direct contact ecotoxicity tests have been developed and introduced, which are useful for characterisation of the risk of contaminated soils due to their interactive nature. Soil no. 1 derived from a site polluted with transformer oil (PCB-free); Soil no. 2 originated from a site contaminated with mazout; Soil no. 3 was contaminated with toxic metals (Zn, Cd, Cu, Pb, As). In most cases, the interactive ecotoxicity tests indicated more harmful effect of the contaminated soil than the tests using soil extracts. The direct contact environmental toxicity tests are able to meet the requirements of environmental toxicology: reliability, sensibility, reproducibility, rapidity and low cost.     

Toxicity of methyl tert-butyl ether to marine organisms: ambient water quality criteria calculation

In response to increasing concerns over the detection of methyl tert-butyl ether (MTBE) in groundwater and surface water and its potential effects in aquatic ecosystems, industry and the United States Environmental Protection Agency (USEPA) began to collaborate in 1997 to develop aquatic toxicity databases sufficient to derive ambient water quality criteria for MTBE consistent with USEPA requirements. Acute toxicity data for seven marine species, chronic toxicity data for an invertebrate, and plant toxicity data were developed to complete the saltwater database. The species tested were Cyprinodon variegatus, Gasterosteus aculeatus, Callinectes sapidus, Mytilus galloprovincialis, Palaemonetes pugio, Rhepoxynius abronius, Americamysis bahia, and Skeletonema costatum. The toxicity tests were conducted in accordance with USEPA and American Society for Testing and Materials testing procedures and Good Laboratory Practice guidelines. Data developed from this study were consistent with existing data and showed that MTBE has low acute and chronic toxicity to the marine species tested. Based upon measured MTBE concentrations, acute effects were found to range from 166 mg MTBE/l for the grass shrimp to 1950 mg MTBE/l for marine mussel. The no-observed effect concentration for the reproduction and growth of mysids was 26 mg MTBE/l during the life cycle test. The toxicity of MTBE to saltwater organisms is comparable to its toxicity to the freshwater species tested. Reported MTBE concentrations in coastal waters are several orders of magnitude lower than concentrations observed to cause effects in marine organisms.     

Environmental impact of aquaculture and countermeasures to aquaculture pollution in China

GOAL, SCOPE AND BACKGROUND: Aquaculture activities are well known to be the major contributor to the increasing level of organic waste and toxic compound in the aquaculture industry. Along with the development of intensive aquaculture in China, concerns are evoked about the possible effects of ever-increasing aquaculture waste both on productivity inside the aquaculture system and on the ambient aquatic ecosystem. Therefore, it is apparent that appropriate waste treatment processes are needed for sustaining aquaculture development. This review aims at identifying the current status of aquaculture and aquaculture waste production in China. MAIN FEATURES: China is the world's largest fishery nation in terms of total seafood production volume, a position it has maintained continuously since 1990. Freshwater aquaculture is a major part of the Chinese fishery industry. Marine aquaculture in China consists of both land-based and offshore aquaculture, with the latter mostly operated in shallow seas, mud flats and protected bays. The environmental impacts of aquaculture are also striking. RESULTS: Case studies on pollution hot spots caused by aquaculture have been introduced. The quality and quantity of waste from aquaculture depends mainly on culture system characteristics and the choice of species, but also on feed quality and management. Wastewater without treatment, if continuously discharged into the aquatic environment, could result in remarkable elevation of the total organic matter contents and cause considerable economy lost. Waste treatments can be mainly classified into three categories: physical, chemical and biological methods. DISCUSSION: The environmental impacts of different aquaculture species are not the same. New waste treatments are introduced as references for the potential development of the waste treatment system in China. The most appropriate waste treatment system for each site should be selected according to the sites' conditions and financial status as well as by weighing the advantages and disadvantages of each system. Strategies and perspectives for sustainable aquaculture development are proposed, with the emphasis on environmental protection. CONCLUSIONS: Negative effects of waste from aquaculture to aquatic environment are increasingly recognized, though they were just a small proportion to land-based pollutants. Properly planned use of aquaculture waste alleviates water pollution problems and not only conserves valuable water resources but also takes advantage of the nutrients contained in effluent. It is highly demanding to develop sustainable aquaculture which keeps stocking density and pollution loadings under environmental capacity. RECOMMENDATIONS AND PERSPECTIVES: The traditional procedures for aquaculture waste treatment, mainly based on physical and chemical means, should be overcome by more site-specific approaches, taking into account the characteristics and resistibility of the aquatic environment. Further research needs to improve or optimize the current methods of wastewater treatment and reuse. Proposed new treatment technology should evaluate their feasibility at a larger scale for practical application.