Evaluation of effect of hazardous contaminants in areas for the abstraction of drinking water.

The lower portion of Taquari River is influenced by compounds from anthropic activities causing concern about the drinking water supplied to cities in the region. The study objective was to investigate the presence of contaminants at drinking water abstraction sites, defining the mutagenic effects of these stressors as an ecosystem quality parameter and its possible effects on human health. Geographic Information System techniques were used to investigate sources of contamination and it was found that agricultural activities predominated with a few medium and high potential pollutant agricultural activities, besides a soil area that was contaminated and undergoing an intervention process. Mutagenic effects were evaluated by Salmonella/microsome assay using TA98, TA97a, TA100, YG1041 and YG1042 strains in the presence and absence of metabolic activation (S9). Mutagenesis found in organic sediment extracts and surface water samples showed the prevalence of direct-acting mutagens at the drinking water abstraction sites. Taquari (Ta032, the sampling points were named according to the initial letters of the river (Ta), followed by the number of kilometers from the mouth) showed the highest mutagenic potency in sediment, while Ta063, at Bom Retiro do Sul, presented it in the water sample. In the Triunfo region (Ta011) there were significant responses in sediment and in water samples. The samples at General Câmara (Ta006) showed the least presence of contaminants. The Allium cepa test applied to sediments in natura showed significant micronucleus induction in Ta032 in accordance with the Salmonella/microssome assay. The test performed on Danio rerio embryos (FET) in the in natura water samples did not present significant responses. Chemical analyses of polycyclic aromatic hydrocarbons and metals already identified as chemical markers in the area indicated a small contribution to the mutagenic potency, calling attention to the fact that other direct-acting pollutants may be present at the drinking water abstraction sites.

Cesium and strontium loads into a combined sewer system from rainwater runoff.

In this study, combined sewage samples were taken with time in several rain events and sanitary sewage samples were taken with time in dry weather to calculate Cs and Sr loads to sewers from rainwater runoff. Cs and Sr in rainwater were present as particulate forms at first flush and the particulate Cs and Sr were mainly bound with inorganic suspended solids such as clay minerals in combined sewage samples. In addition, multiple linear regression analysis showed Cs and Sr loads from rainwater runoff could be estimated by the total amount of rainfall and antecedent dry weather days. The variation of the Sr load from rainwater to sewers was more sensitive to total amount of rainfall and antecedent dry weather days than that of the Cs load.

Physical-chemical treatment of rainwater runoff in recovery and recycling companies: Pilot-scale optimization.

Pilot-scale optimisation of different possible physical-chemical water treatment techniques was performed on the wastewater originating from three different recovery and recycling companies in order to select a (combination of) technique(s) for further full-scale implementation. This implementation is necessary to reduce the concentration of both common pollutants (such as COD, nutrients and suspended solids) and potentially toxic metals, polyaromatic hydrocarbons and poly-chlorinated biphenyls frequently below the discharge limits. The pilot-scale tests (at 250 L h(-1) scale) demonstrate that sand anthracite filtration or coagulation/flocculation are interesting as first treatment techniques with removal efficiencies of about 19% to 66% (sand anthracite filtration), respectively 18% to 60% (coagulation/flocculation) for the above mentioned pollutants (metals, polyaromatic hydrocarbons and poly chlorinated biphenyls). If a second treatment step is required, the implementation of an activated carbon filter is recommended (about 46% to 86% additional removal is obtained).

Enhancing bioretention efficiency for pollutant mitigation in stormwater runoff: Exploring ecosystem cycling dynamics amidst temporal variability.

In this study, three distinct bioretention setups incorporating fillers, plants, and earthworms were established to evaluate the operational efficiency under an ecosystem concept across varying time scales. The results revealed that under short-term operating conditions, extending the drying period led to a notable increase in the removal of NO3--N, total phosphorus (TP), and chemical oxygen demand (COD) by 5 %-7%, 4 %-12 %, and 5 %-10 %, respectively. Conversely, under long-time operating conditions, the introduction of plants resulted in a significant boost in COD removal by 10 %-20 %, while the inclusion of earthworms improved NH4+-N and NO3--N removal, especially TP removal by 9 %-16 %. Microbial community analysis further indicated the favorable impact of the bioretention system on biological nitrogen and phosphorus metabolism, particularly with the incorporation of plants and earthworms. This study provides a reference for the operational performance of bioretention systems on different time scales.

Potential toxic heavy metals in village rainwater runoff of antimony mining area, China: Distribution, pollution sources, and risk assessment.

The potential toxic heavy metal runoff from antimony mining areas poses a serious threat to the water environment and the health of residents in the village. The study found that the average concentrations of As, Sb, Cr, Pb, and Cd in the runoff were 0.1237, 0.1148, 0.0332, 0.0140, and 0.0013 mg/L, which were higher than the normal average concentrations in the water environment of 0.018, 0.0009, 0.05, 0.012, and 0.000013 mg/L, respectively.Sb and As are severely polluted, while Cd, Pb, and Cr have lower pollution levels. The coefficients of variation for As, Sb, Cr, Pb, and Cd range from 0.079 to 1.051, with Sb showing exceptionally high variability. Heavy metal elements Pb, Cd, and Sb accumulate in the southeastern area of the village, with Sb concentrations decreasing from the southeast to the northwest. As is mainly distributed in the northeastern part of the village, while Cr is primarily found in the central-western region. Source analysis indicates that As and Sb originate from mining and industrial activities, dust deposition, and domestic sewage. Cr comes from the natural geological background and metal product industry, Pb from lead-acid batteries, industrial activities, and gasoline additives, and Cd from fertilization in residential green areas and pesticide use. Health risk analysis reveals that the hazard index (HI) values for As and As in the water environment are 1.49 and 2.31, respectively, both exceeding 1, posing a serious threat to the health of village residents. The HI values for Pb, Cr, and Cd elements are all below 1, indicating lower risks. This study identified that Sb in the antimony ore area and its associated metal element As are the main elements leading to potential heavy metal pollution in the runoff of village residential areas, providing direction for subsequent water environment restoration work.

Processes of nitrogen removal from rainwater runoff in bioretention filters modified with ceramsite and activated carbon.

Conventional bioretention filters lack satisfactory performance in nitrogen removal. In this study, we used a mixture of cultivated soil and river sand as the bioretention filter to remove nitrogen pollutants from simulated rainwater runoff. To improve its permeability and nitrogen removal performance, both activated carbon and ceramsite were used as additives. The nitrogen removal processes and its mass accumulation in the modified bioretention filters were studied. The contribution of adsorption and biotransformation processes, together with the effects of percolate rate on nitrogen removal performance was explored. The results showed that an activated carbon layer in the bioretention filters could obviously improve nitrogen removal efficiencies, but its location made no significant difference in nitrogen removal performance. Bioretention filters modified with 20% of ceramsite could achieve the optimal percolate rate and nitrogen removal efficiencies. At given conditions, the average removal efficiencies of ammonium nitrogen (NH3-N), nitrate-nitrogen (NO3-N), and total nitrogen (TN) by the modified bioretention filter reached 80.27%, 41.48%, and 59.45%, respectively. During the leaching processes, organic nitrogen originated in the filter materials can be mineralised into NH3-N, then be denitrified and completely removed in the anaerobic environment under flooding conditions. Biotransformation in the modified bioretention filters caused a reduction of NH3-N removal efficiency by 15.41% and an increase of NO3-N removal efficiency by 31.03%. The modified bioretention filter can withstand a long-term operation. Compared with NO3-N and TN, the pollutant of NH3-N in rainwater runoff is not easy to form a mass accumulation in the modified bioretention filter.Highlights The modified bioretention filter showed high percolation rate and nitrogen removal.Hydraulic residence time is a critical design parameter to achieve nitrogen removal.NH3-N is not easy to form a mass accumulation in the filler media as NO3-N.Biodegradation increased NO3-N removal efficiency by 31.03% at given conditions.

Urban pipeline rainwater runoff is an important pathway for land-based microplastics transport to inland surface water: A case study in Beijing.

Microplastics (MPs) as new environmental pollutants are receiving increasing attention worldwide. Urban rainwater runoff plays an important role in facilitating the migration of land-based MPs to surface water. Previous research has focused predominantly on aquatic ecosystems, whereas research on this migration pathway and the characteristics of MPs in rainwater pipelines draining from different land-use types is still lacking. This study investigated the abundance and characteristics of MPs in rainfall and pipeline rainwater runoff from main roads, office complexes, an agricultural experiment station, and residential areas during different rainfall periods in Haidian District, Beijing, China. Microplastic abundance in pipeline rainwater runoff ranged from 1.6 to 29.6 items L-1, of which 0.7 to 6.0 items L-1 were derived from rainfalls, accounting for 24.0 % to 77.4 % of the total. Microplastic abundances in rainfall and pipeline rainwater runoff decreased significantly as rainfall events progressed. The proportions of MPs < 1 mm in rainfall (38.0 %) and rainwater runoff (44.5 %) were the largest. Average MPs abundance was the highest in rainwater runoff from the main road area and lowest in the office area (p < 0.05). The abundance of polyester fibers in rainwater runoff from the residential area was significantly higher than that in other areas, while the main road area had the highest abundance of films (p < 0.05). Overall, 72 % of MPs in rainfall were fibers, and most were composed of polyester, while the MPs in rainwater runoff were mainly fragments (41.2 %) and fibers (35.3 %) composed mainly of polypropylene, polyethylene, and polyester. This study shows that urban pipeline rainwater runoff is one of the main pathways for land-based MPs transport to surface waters, and provides a scientific reference for preventing and controlling MPs entering water bodies through rainwater pipelines.

Removal characteristics of heavy metal ions in rainwater runoff by bioretention cell modified with biochar.

As a form of pollution source control and a low-impact development measure, bioretention is a convenient, economical, and effective method for the removal of heavy metals from stormwater runoff, which can adapt to the randomness and uncontrollability of non-point source pollution. However, few studies have assessed the performance of bioretention in the simultaneous removal of multiple heavy metals and the impact of heavy metal migration on the bioretention life cycle. In this study, the removal rates of various heavy metals: copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd), were enhanced using a biochar modified bioretention cell, as compared to the traditional sandy soil bioretention process. Following treatment with the biochar modified bioretention cell, the average concentrations of Cu, Zn, Pb, and Cd were 55%, 61%, 19.66%, and 36.43% lower than the traditional sandy soil bioretention effluent, respectively. These results show that biochar significantly improves the removal of heavy metals by the bioretention process, especially Cu and Zn. This study also evaluated the effect of biochar on the inhibition of heavy metal migration in the filler material, by sampling and analysing the filler and retained water at different filler depths, then repeating the filler leaching experiment after simulated rainfall. The content of heavy metals at a filler depth of 45 cm in the traditional sandy soil bioretention system, was significantly higher than in the biochar modified bioretention system, showing that biochar plays an important role in the inhibition of heavy metal migration.

[Analysis of Rainwater Runoff Pollution Characteristics of Various Typical Underlying Surfaces in Ningbo].

The pollution of rainwater runoff in urban areas can cause nutrient enrichment and eutrophication in receiving waters. To explore the pollution characteristics of rainwater runoff in Ningbo, eight sampling campaigns were carried out during rainfall events from 2009 to 2019. Samples of rainwater runoff were collected from underlying surfaces of roofs, squares, grassland, main roads, and the roads in commercial streets and residential districts. The concentrations of runoff pollutants, their sources and correlations, and first flush effects were studied using frequency statistical analysis and correlation analysis. The average event mean concentrations of the chemical oxygen demand (COD), ammonia nitrogen, total nitrogen, total phosphorus, and total suspended solids (TSS) in the rainwater runoff in Ningbo were in the ranges of 23.88-102.31, 0.40-1.69, 3.41-8.71, 0.09-0.50, and 37.6-323.4 mg·L-1, respectively. Apart from the square surfaces, the COD and total nitrogen pollution of the underlying surfaces was severe. The ammonia nitrogen concentrations from the roof, commercial street, and residential district surfaces were significantly higher (P<0.05) than those from the square, grassland, and main road surfaces. The concentrations of total phosphorus from the commercial street, main road, and grassland surfaces were significantly higher (P<0.05) than those of the other underlying surfaces. The correlations of TSS with COD, ammonia nitrogen, and total phosphorus showed that the pollutants and TSS have the same original sources in roof, square, main road, and commercial street runoff, while ammonia nitrogen and total nitrogen have the same original sources in runoff from grassland and residential areas. Under the meteorological conditions of light and moderate rain, the first flush effects of ammonia nitrogen in the runoff of roofs and grassland were observed clearly, whereas this was not the same for the pollutants of total nitrogen and total phosphorus in the residential area, main road, and square runoff.

Filler improvement and purification effects of constructed rapid infiltration facility.

Purification effects of constructed rapid infiltration system with two main fillers (coarse sand or medium coarse sand) and different addition proportion (5%, 10%, or 15%) modifiers (sponge iron, blast furnace slag, or zeolite) on rainwater runoff were studied through filter column tests. A set of constructed rapid infiltration system test device was designed, which included 9 rainwater filter columns. The test results showed that the permeability of artificial fillers blended with modifiers could have the promotion with varying degrees. There were differences in the characteristics of the modifiers, so the artificial fillers blended with different modifiers had a significant difference for the purification effects on each pollutant. In view of the overall situations, the pollutant removal effects of artificial fillers with two or more modifiers had a smaller gap, and the reduction effects were good, ranging from 38.95 to 46.25% when the main filler is coarse sand and from 46.29 to 49.46% while main filler is medium coarse sand. It was worth noting that the artificial fillers blended with sponge iron showed a slight harden after prolonged used; however, it had little influence on the permeability and water purification effects.

Physical-chemical treatment of rainwater runoff in recovery and recycling companies: lab-scale investigation.

Scrap material recovery and recycling companies are producing wastewater in which common pollutants (such as COD, nutrients and suspended solids), toxic metals, polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB) frequently can exceed the discharge limits. Lab-scale optimisation of different possible physical-chemical treatment techniques was performed on the wastewater originating from three different companies in view of further testing at pilot-scale testing and implementation at full-scale. The lab-scale tests demonstrate that sedimentation or hydrocyclone treatment as stand-alone technique cannot be used for proper treatment of this type of wastewater. Dual bed filtration or coagulation/flocculation proved to be more promising with removal efficiencies of about 71-95% (dual bed filtration) and 61-97% (coagulation/flocculation) for the above-mentioned pollutants (metals, PAH and PCB).

Polluted rainwater runoff from waste recovery and recycling companies: Determination of emission levels associated with the best available techniques.

Rainwater falling on outdoor storage areas of waste recovery and recycling companies becomes polluted via contact with the stored materials. It contains various pollutants, including heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls, and is characterized by a highly fluctuating composition and flow rate. This polluted rainwater runoff is legally considered as industrial wastewater, and the polluting substances contained in the rainwater runoff at the point of discharge, are considered as emissions into water. The permitting authorities can set emission limit values (discharge limits) at the point of discharge. Best available techniques are an important reference point for setting emission limit values. In this paper, the emission levels associated with the best available techniques for dealing with polluted rainwater runoff from waste recovery and recycling companies were determined. The determination is based on an analysis of emission data measured at different companies in Flanders. The data show that a significant fraction of the pollution in rainwater runoff is associated with particles. A comparison with literature data provides strong indications that not only leaching, but also atmospheric deposition play an important role in the contamination of rainwater at waste recovery and recycling companies. The prevention of pollution and removal of suspended solids from rainwater runoff to levels below 60mg/l are considered as best available techniques. The associated emission levels were determined by considering only emission data from plants applying wastewater treatment, and excluding all samples with suspended solid levels >60mg/l. The resulting BAT-AEL can be used as a reference point for setting emission limit values for polluted rainwater runoff from waste recovery and recycling companies. Since the BAT-AEL (e.g. 150µg/l for Cu) are significantly lower than current emission levels (e.g. 300µg/l as the 90% percentile and 4910µg/l as the maximum level for Cu), this will result in a significant reduction in emissions into water.

Leaching behaviour of different scrap materials at recovery and recycling companies: full-, pilot- and lab-scale investigation.

Scrap material recovery and recycling companies are confronted with waste water that has a highly fluctuating flow rate and composition. Common pollutants, such as COD, nutrients and suspended solids, potentially toxic metals, polyaromatic hydrocarbons and poly chlorinated biphenyls can exceed the discharge limits. An analysis of the leaching behaviour of different scrap materials and scrap yard sweepings was performed at full-scale, pilot-scale and lab-scale in order to find possible preventive solutions for this waste water problem. The results of these leaching tests (with concentrations that frequently exceeded the Flemish discharge limits) showed the importance of regular sweeping campaigns at the company, leak proof or covered storage of specific scrap materials and oil/water separation on particular leachates. The particulate versus dissolved fraction was also studied for the pollutants. For example, up to 98% of the polyaromatic hydrocarbons, poly chlorinated biphenyls and some metals were in the particulate form. This confirms the (potential) applicability of sedimentation and filtration techniques for the treatment of the majority of the leachates, and as such the rainwater run-off as a whole.

Rainwater runoff retention on an aged intensive green roof.

Urban areas are characterised by large proportions of impervious surfaces which increases rainwater runoff and the potential for surface water flooding. Increased precipitation is predicted under current climate change projections, which will put further pressure on urban populations and infrastructure. Roof greening can be used within flood mitigation schemes to restore the urban hydrological balance of cities. Intensive green roofs, with their deeper substrates and higher plant biomass, are able to retain greater quantities of runoff, and there is a need for more studies on this less common type of green roof which also investigate the effect of factors such as age and vegetation composition. Runoff quantities from an aged intensive green roof in Manchester, UK, were analysed for 69 rainfall events, and compared to those on an adjacent paved roof. Average retention was 65.7% on the green roof and 33.6% on the bare roof. A comprehensive soil classification revealed the substrate, a mineral soil, to be in good general condition and also high in organic matter content which can increase the water holding capacity of soils. Large variation in the retention data made the use of predictive regression models unfeasible. This variation arose from complex interactions between Antecedant Dry Weather Period (ADWP), season, monthly weather trends, and rainfall duration, quantity and peak intensity. However, significantly lower retention was seen for high rainfall events, and in autumn, which had above average rainfall. The study period only covers one unusually wet year, so a longer study may uncover relationships to factors which can be applied to intensive roofs elsewhere. Annual rainfall retention for Manchester city centre could be increased by 2.3% by a 10% increase in intensive green roof construction. The results of this study will be of particular interest to practitioners implementing greenspace adaptation in temperate and cool maritime climates.