An innovative approach of Drinking Water Quality Index—A case study from Southern Tamil Nadu,India

The aim of the present study is to exhaust the limitations of conventional reputed Water Quality Index (WQI) methodologies through the proposed reliable Drinking Water Quality Indexing (DWQI) system. Slight modifications were carried out in the methodology of the DWQI development which were parameter categorization, development of sub-index with regression statistics and aggregation function with Min–Max operator. Twenty-two water quality parameters were selected for quality evaluation. The proposed DWQI was compared with conventional methodologies of arithmetic DWQI and geometric DWQI and evaluated with a case study. A data set of 24 ground water samples collected from Southern Tamil Nadu, India was made to illustrate the application and feasibility of the index.The results of the case study revealed that arithmetic DWQI scores were higher than the proposed and geometric DWQI while geometric DWQI scores were lower than the proposed DWQI scores. All the indices were well correlated (r ≥ +0.98) with each other. The arithmetic DWQI exhibited significant difference (P < 0.001) with other indices but the proposed DWQI scores had insignificant variations (P = 0.40) with geometric DWQI scores. The comparison of different forms of indices showed that the proposed DWQI was the most reliable indexing system than the others which diminished the sensitivity and eclipsing problems of conventional indexing system.     

Assessment of water quality in groundwater resources of Iran using a modified drinking water quality index (DWQI)

An innovative drinking water quality index (DWQI) based on the Canadian DWQI was developed as “modified DWQI” and applied for assessing the water quality in all of the groundwater resources that are used as the source of drinking water in urban areas of Iran in 2011. Assignment of weight factors for input parameters was the modification carried out in the DWQI. In development of the modified DWQI, twenty-three water quality parameters and relevant Iranian standards for drinking water quality were selected as input parameters and benchmarks, respectively. The modified DWQI is calculated for each sampling station over one year using three factors: the number of parameters that excurse benchmarks, the number of measurements in a dataset that excurse benchmarks and the magnitude of excursion from benchmarks in the violator measurements. The modified DWQI contains two sub-indices: health-based index as “modified HWQI” and acceptability index as “modified AWQI”. The modified DWQI and its sub-indices scores range from 0 to 100 and classify water quality in five categories as poor, marginal, fair, good and excellent, respectively. The results of the case study revealed that the nationwide average scores of the modified DWQI, HWQI and AWQI in the groundwater resources were 85, 79 and 91, respectively and overall situation of water quality in the groundwater resources was described as good. According to the modified DWQI value, about 95% of the groundwater flowrates were in the good condition, also in 3 and 2% of the groundwater flowrates, water quality was determined to be fair and marginal, respectively. This study indicated that the modified DWQI and its sub-indices could describe the overall water quality of water bodies easily, reliably and correctly and have the potential suitability for extensive application all over the world.     

Water quality assessment of Tal Chhapar Wildlife Sanctuary using water quality index (CCME WQI)

The present study was undertaken from June 2015 to May 2017 in Tal Chhapar Wildlife Sanctuary (TWS), Churu, Rajasthan that represents one of the unique and important grassland ecosystems in the Thar desert of India but has not been assessed ecologically. In this work the water quality assessment of the area is carried out in terms of physicochemical parameters and water quality index to fill this gap. The surface water samples were collected from the water surface with two replicates per sampling occasion for the summer, monsoon, and post-monsoon seasons. The physicochemical analysis for eight parameters were carried out following prescribed methods, viz., pH-by pH meter, total dissolved solids (TDS) -gravimetric analysis and filtration, chloride- silver nitrate titration, sulphate- turbidimetric, phosphate-stannous chloride, nitrate-brucine, calcium- EDTA titration, and iron- calorimetric methods. The relationship between the parameters was analyzed using Pearson's correlation analysis, and the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) was calculated from these parameters. The study revealed water to be slightly alkaline (7.27–7.63) in the area. Most of the physicochemical parameters of water were found to be within the acceptable limits of the Bureau of Indian Standards (BIS) except for TDS and phosphate. The TDS showed a very strong to moderate correlation with chloride (r = 0.97), iron (r = 0.79), sulphate (r = 0.58), and calcium (r = 0.52) that revealed these ions were the major components in the makeup of the dissolved solids in the water sample. The CCME WQI indicated the water quality was fair and suitable for drinking purposes for wildlife in the area. In absence of any such prior study in the area, the overall findings of the present work is highly significant that can be used by the management authorities for future environmental monitoring and holistic development of the area.     

Impact of landscape pattern at multiple spatial scales on water quality: A case study in a typical urbanised watershed in China

Buffer zones along rivers and streams can provide water quality services by filtering nutrients, sediment and other contaminants from the surface. Redundancy analysis was used to determine the influence of the landscape pattern at the entire catchment scale and at multiple buffer zone scales (100 m, 300 m, 500 m, 1000 m and 1500 m) on the water quality in a highly urbanised watershed. Change-point analysis was further applied to estimate the specific locations along a gradient of landscape metric that result in a sudden change in the water quality variable. The landscape characteristics for 100 m buffer zones appeared to have a slightly greater influence on the water quality than the entire catchment. The patch density of urban land and the large patch index of water were recognised as the dominant variables influencing the water quality for a 100 m buffer zone. The result of change-point analysis indicated key interval values of the two landscape metrics within the 100 m buffer zone. When the patch density of urban land was >30–40 n/100 ha and the largest patch index of water was >2.5–3.5%, the watershed water quality appeared to be better protected.     

Effect of water temperature on reproductive performance and offspring quality of rare minnow,Gobiocypris rarus

Water temperature plays a significant role in the reproductive processes of temperate fishes. In the present study, the effects of water temperature on the reproductive performance and offspring quality of rare minnow (Gobiocypris rarus) were evaluated by cultured parent fish at different temperature (18～30 ℃) in a 2-month trial. The results revealed that rare minnows could spawn continuously within the range from 18 ℃ to 30 ℃, and these at 24 ℃ and 27 ℃ spawned every 3–4 days. Batch size of rare minnow increased with increasing water temperature, while egg production increased with increasing water temperature and then decreased at 30 ℃. High water temperature (30 ℃) had significantly adverse effects on fertilization rate and hatching rate (P<0.05). It was found that the oocyte growth at 18 ℃, 21 ℃, and 30 ℃ were slower than those at 24 ℃ and 27 ℃. Histologic analysis further showed that low temperature (18 ℃ and 21 ℃) slowed down vitellogenesis and oocyte maturation, while high temperature (30 ℃) had suppressive effects on oocyte maturation and ovulation. Based on present results, it was concluded that 24–27 ℃ was optimal breeding temperature for rare minnows and water temperature higher than 30 ℃ resulting from climate change would pose a threat to its wild populations.     

Chlorination-mediated EPS excretion shapes early-stage biofilm formation in drinking water systems

Microbial surface adhesion to surfaces and subsequent biofilm establishment are ubiquitous in drinking water systems, which often contribute to deteriorated water quality. Disinfectants are common agents applied to drinking water controlling microbial propagation, yet the underlying mechanisms of how disinfectants function to regulate microbial activity and thereby biofilm development remains elusive. We experimentally studied the effects of chlorination on extracellular polymeric substance (EPS) production, and its impacts on early-stage biofilm formation in a model drinking water system. Results showed that low-level chlorine (≤ 1.0 mg/L) stimulated microbial EPS (especially of proteins) excretion that favored early-stage biofilm formation. Microbes experiencing higher chlorination (>1.0 mg/L) exhibited clearly suppressed growth associated with reduced EPS release, consequently yielding less biofilm formation. Removal of cell-attached proteins and polysaccharides diminished biofilm formation, which highlighted the critical role of EPS (especially protein components) in biofilm development. A negative correlation between chlorination-mediated microbial protein production and cell surface charge suggested that chlorine disinfection may modify cell surface properties through regulation of microbial EPS excretion and thereby mediate biofilm formation. With these quantitative estimations, this study provides novel insights into how chlorination-mediated EPS excretion shapes early-stage biofilm formation, which is essential for practical functioning of drinking water systems.     

The effect of water temperature and velocity on barnacle growth: Quantifying the impact of multiple environmental stressors

Organisms employ a wide array of physiological and behavioral responses in an effort to endure stressful environmental conditions. For many marine invertebrates, physiological and/or behavioral performance is dependent on physical conditions in the fluid environment. Although factors such as water temperature and velocity can elicit changes in respiration and feeding, the manner in which these processes integrate to shape growth remains unclear. In a growth experiment, juvenile barnacles (Balanus glandula) were raised in dockside, once-through flow chambers at water velocities of 2 versus 19 cm s⁻¹ and temperatures of 11.5 versus 14 °C. Over 37 days, growth rates (i.e., shell basal area) increased with faster water velocities and higher temperatures. Barnacles at high flows had shorter feeding appendages (i.e., cirri), suggesting that growth patterns are unlikely related to plastic responses in cirral length. A separate experiment in the field confirmed patterns of temperature- and flow-dependent growth over 41 days. Outplanted juvenile barnacles exposed to the faster water velocities (32±1 and 34±1 cm s⁻¹; mean±SE) and warm temperatures (16.81±0.05 °C) experienced higher growth compared to individuals at low velocities (1±1 cm s⁻¹) and temperatures (13.67±0.02 °C). Growth data were consistent with estimates from a simple energy budget model based on previously measured feeding and respiration response curves that predicted peak growth at moderate temperatures (15 °C) and velocities (20–30 cm s⁻¹). Low growth is expected at both low and high velocities due to lower encounter rates with suspended food particles and lower capture efficiencies respectively. At high temperatures, growth is likely limited by high metabolic costs, whereas slow growth at low temperatures may be a consequence of low oxygen availability and/or slow cirral beating and low feeding rates. Moreover, these results advocate for approaches that consider the combined effects of multiple stressors and suggest that both increases and decreases in temperature or flow impact barnacle growth, but through different physiological and behavioral mechanisms.     

Comparative study of ecological indices for assessing human-induced disturbance in coastal wetlands of the Laurentian Great Lakes

Several ecological indices have been developed to evaluate the wetland quality in the Laurentian Great Lakes. One index, the water quality index (WQI) can be widely applied to wetlands and produces accurate measurements of wetland condition. The WQI measures the degree of water quality degradation as a result of nutrient enrichment and road runoff. The wetland fish index (WFI), wetland zooplankton index (WZI), and the wetland macrophyte index (WMI), are all derived from the statistical relationships of biotic communities along a gradient of deteriorating water quality. Compared to the WQI, these indices are less labor-intensive, cost less, and have the potential to produce immediate results. We tested the relative sensitivity of each biotic index for 32 Great Lakes wetlands relative to the WQI and to each other. The WMI (r² = 0.84) and WFI (r² = 0.75) had significant positive relationships (P < 0.0001) with the WQI in a linear and polynomial fashion. Slopes of the WMI and WFI were similar when comparing the polynomial regressions (ANCOVA; P = 0.117) but intercepts were significantly different (P = 0.004). The WZI had a positive relationship with the WQI in degraded wetlands and a negative relationship in minimally impacted wetlands. The strengths and weaknesses of each index can be explained by the interactions among fish, zooplankton, aquatic plants and water chemistry. The distribution of different species indicative of low and high quality in each index provides insight into the relative wetland community composition in different parts of the Great Lakes and helps to explain the differences in index scores when different organisms are used. Our findings suggest that the WMI and WFI produce comparable results but the WZI should not be used in the minimally impacted wetlands without further study.     

Remote sensing of chlorophyll-a concentration for drinking water source using genetic algorithms (GA)-partial least square (PLS) modeling

Accurate estimation of phytoplankton chlorophyll-a (Chl-a) concentration in turbid waters through remote sensing is a challenge due to the optical complexity of water constituents. Reflectance spectra and concurrent water quality parameters of 225 samples across the Shitoukoumen Reservoir, the drinking water resource for Changchun City, were used to retrieve Chl-a concentration with high total suspended matter (TSM) during 2006–2008. A combination of genetic algorithms and partial least square (GA-PLS) model was established for Chl-a retrieval through GA to select sensitive spectral variables and PLS for regression. To compare GA-PLS performances, the widely accepted three-band algorithm was implemented for Chl-a concentration estimation. Both GA-PLS and the three-band algorithm have stable performance for the aggregated dataset (R² = 0.85 and 0.81; RPD = 3.95 and 3.61; relative RMSE = 31.7% and 34.2%), with the GA-PLS model performing marginally better. The temporal transferability of the models was validated with the dataset collected in 2006 and 2007 respectively as independent dataset, showing that GA-PLS outperformed the three-band algorithm. Our result also indicated that relative error [(Chl-a_predicted − Chl-a_measured) / Chl-a_measured] showed good linear relation to TSM: Chl-a ratio (R² = 0.84), which implied that TSM concentration exerted significant impact on the accuracy of Chl-a estimation in this case study. As the results were derived from a large number of samples representing a wide range of spatiotemporal variations of pigment under TSM (3.7–472.8 mg/L) concentration influence, the GA-PLS model has great potential for Chl-a estimation for inland waters with similar backgrounds. Nevertheless, the three-band algorithm also has its own merit considering its simplicity for implementation.     

Heavy metal pollution in surface water and sediment: A preliminary assessment of an urban river in a developing country

The concentration and chemical fractionation of globally alarming six heavy metals (Cr, Ni, Cu, As, Cd and Pb) were measured in surface water and sediment of an urban river in Bangladesh. The decreasing trend of metals were observed in water as Cr > Cu > As > Ni > Pb > Cd and in sediment as Cr > Ni > Cu > Pb > As > Cd. The level of studied metals exceeded the safe limits of drinking water, indicated that water from this river is not safe for drinking and/or cooking purposes. However, the investigated metals showed low mobility except for Cd and Pb which could pose a severe threat to the aquatic environment. Contamination factor (CF) and geoaccumulation index (I_geo) demonstrated that most of the sediment samples were moderately to heavily contaminated by Cr, As, Cd and Pb. The pollution load index (PLI) values were above one (>1) indicates progressive deterioration of the sediment quality. The extent of pollution by heavy metals in the river Korotoa implies that the condition is much frightening to the biota and inhabitants in the vicinity of the river as well.     

Effects of wetland construction on water quality in a semi-arid catchment degraded by intensive agricultural use

Many factors can influence the improvement of water quality in surface-flow constructed wetlands (SFW). To test if water quality was improved, especially in nutrient and salt content, after passage through SFW, 11 wetland plots of various sizes (50, 200, 800 and 5000 m²) were established within constructed wetlands on agricultural soils in the Ebro River basin (NE Spain) that had been affected by salinization. A set of 15 water quality parameters (e.g., nutrients, salts, sediments, and alkalinity) was obtained from samples collected at the inflow and outflow of the wetlands during the first 4 years after the wetlands were constructed. NO₃-N retention rates were as high as 99% in the largest (5000 m²) wetlands. After 4 years, total phosphorus was still being released from the wetlands but not salts. Over the same period, in small wetlands (50, 200, and 800 m²), retention rate relative to the input of NO₃-N increased from 40% to almost 60%. Retention of NO₃-N amounted to up to 500 g N m^?2 per year, for an average load concentration at inflow of ～20 mg l^?1. Release of Na⁺ declined from 16% to 0–2% by volume, for an average load concentration at inflow of ～70 mg l^?1. At the current retention rate of NO₃-N (76–227 g m^?2 per year), 1.5–4% of the catchment should be converted into wetlands to optimize the elimination of NO₃-N.     

The influence of drinker location and colour on drinking behaviour and water intake of newborn pigs under hot environments

The effect of drinker location within the farrowing crate in relation to its microenvironment and the effect of dispenser colour on drinking behaviour and water intake of newborn pigs for the first two days of their lives were studied. In the first trial, 16 sows were randomly assigned to four treatment groups with the piglet's water dispenser placed in the front right (FR), front left (FL), back right (BR) or back left (BL) corner of the farrowing pen, respectively. In the second trial nine sows were randomly assigned to three treatment groups with the piglets’ water dispenser, placed in the front left corner of the farrowing pen, and coloured as red (CR), green (CG) or blue (CB), respectively. Trials commenced between 08:00 and 10:00 h on the first morning after the litters were born and the piglets’ age was considered to be zero (“age”) by that time.The average age of the piglets at their first visit to water dispensers was 15.9 ± 1.8 h. The newborn pigs visited the drinker more frequently (P < 0.001) during daytime than during night, with two peaks soon after sow feeding time. The duration of drinking time was long at the time of higher (noon) and shorter at the time of lowest (early morning) temperatures (P < 0.01) in the farrowing house, respectively. The greatest attention at the drinkers occurred soon after suckling (P < 0.001). The longest time spends at the drinker during the first visits and decreased as the pigs visited dispensers repeatedly. The profile of visit frequency and duration differed between piglet sexes (P < 0.001). The pigs that did not visit the drinker grew slower and were lighter at 48 h of age than the pigs visited the drinker. First visit and overall mean visit age were significantly shorter for BL than for FR and BR groups. Piglets visited the FL drinker for shorter time than the others. Water consumption per pig/24 h was lower for FL and higher for BL groups (P < 0.05). Water consumption was higher for CR and CB groups than for CG group. The overall mean visit age was shorter for CG than for CB group. Significant interactions were observed between sex and colour groups for the number of visits (P < 0.05). The results of the present study revealed that water dispenser use by newborn piglets is characterised by diurnal and between two successive milk consumptions distributions. Water consumption by piglets from birth to 48 h of their lives is strongly influenced by water dispenser location in the farrowing pen and the dispenser colour. It also appears that males and females behave differently to the three colour dispensers used in this study.     

An integrated constructed wetland to treat contaminants and nutrients from dairy farmyard dirty water

Water pollution by agriculture can include inappropriately managed dairy farmyard dirty water. In Ireland, dairy farmyard dirty water includes farmyard runoff, parlour washings, and silage/farmyard manure effluents. The objectives of this study were to determine (i) the quality and quantity of dirty water generated at a farm-scale and (ii) the seasonal effectiveness of a constructed wetland to treat farmyard dirty water. The wetland system was 4800 m² in area and treated dirty water from a 42-cow organic dairy unit with an open yard area of 2031 m². Monthly dirty water inflow rate to the wetland ranged between 3.6 and 18.5 m³ d⁻¹. Farmyard dirty water accounted for 27% of hydrological inputs to the wetland, whereas rainfall on wetland, along with wetland bank inflows accounted for 45 and 28%, respectively. Farmyard dirty water quality and quantity did not vary with season. Yearly mass loads discharged to the wetland were 47 ± 10 kg yr⁻¹ of soluble reactive phosphorus (SRP), 128 ± 35 kg yr⁻¹ of NH₄⁺, 5484 ± 1433 kg yr⁻¹ of organic material as measured by five-day biological oxygen demand (BOD₅), and 1570 ± 465 kg yr⁻¹ of total suspended solids (TSS). Phosphorus retention by the wetland varied with season (5–84%) with least amounts being retained during winter.     

Nutrient concentrations in tidal creeks as indicators of the water quality role of mangrove wetlands in Southwest Florida

Coastal mangroves have the potential to improve the water quality of urban and rural runoff before it is discharged into adjacent coastal bays and oceans; but they also can be impaired by excessive pollutants from upstream. Nutrients (phosphorus and nitrogen), salinity, and other water quality parameters were measured in five mangrove tidal creeks in different hydrogeomorphic and urbanization settings during high and low tides over a calendar year of wet (June and August 2015) and dry (February and April 2016) seasons in the Greater Naples Bay area in Southwest Florida, USA. Nutrient concentrations (ave. ± std error) in the tidal creeks were 0.055 ± 0.008 mg-P/L for total phosphorus (TP) and 0.610 ± 0.020 mg-N/L for total nitrogen (TN), with an average N:P ratio of 11.4:1. Average wet season TP (0.075 ± 0.010 mg-P/L) was significantly higher than the dry season TP (0.033 ± 0.003 mg-P/L; p < 0.01, f = 15.17, f_crit = 3.89) and the average wet season TN (0.75 ± 0.03 mg-N/L) was significantly higher than dry season TN (0.52 ± 0.02 mg/L; p < 0.01, f = 64.14, f_crit = 3.89), suggesting that urban stormwater runoff is directly or indirectly affecting the nutrient conditions in these mangroves. Significant differences in nutrient concentrations between low tide and high tide were not found for either TP (p = 0.43, f = .63, f_crit = 3.88) or TN (p = 0.20, f = 1.66, f_crit = 3.89). These differences were confirmed by a PCA and cluster analyses, which found differences to be seasonal. We could not conclude from these results whether these five mangrove wetlands were sources nor sinks of nutrients based simply on the measurement of nutrient concentrations. But we illustrated that nutrient concentrations were indicators of the mangroves’ hydrogeomorphic settings, their tidal fluxes from Naples Bay, and the Bay's upstream watersheds, and less by direct urban runoff.     

Assessing the ecological stress in a Garonne River stretch,southwest France

In order to assess the level of ecological stress caused by the pollution from local disturbances in a stretch of the Garonne River, France, we applied the Abundance-Biomass Comparison (ABC) index, using fish assemblages. Data were collected in a 10-year span (1992–2002) in a reference site and in two pollution-exposed sites. The ABC index mean value in the reference site (S1) was 0.03 ± 0.002 (95% Confidence Interval – CI); for the polluted sites (S2 and S3), the values were −0.09 ± 0.002 (95% CI) and −0.12 ± 0.002 (95% CI), respectively. The ABC index showed that, besides flow variations, both downstream sites are statistically different (p < 0.05) from the reference site, but all three seem to be under moderate stress. Furthermore, we related our ABC scores to water quality and flow regime variables in the reference site and one of the polluted sites by means of a cluster analysis. The results showed that, in the reference site, the ABC scores are closely related to the flow regime, while in the polluted site, downstream a urban area, ABC is related to water quality variables such as phosphates and total phosphorous. We argue that ecological indicators can help decisions on environmental damage liability.     

Diurnal exchanges of CO2 and CH4 across the water–atmosphere interface in a water chestnut meadow (Trapa natans L.)

CH₄ and CO₂ fluxes across the water–atmosphere interface were measured over a 24 h day–night cycle in a shallow oxbow lake colonized by the water chestnut (Trapa natans L.) (Lanca di Po, Northern Italy). Only exchanges mediated by macrophytes were measured, whilst gas ebullition was not considered in this study. Measurements were performed from 29 to 30 July 2005 with short incubations, when T. natans stands covered the whole basin surface with a mean dry biomass of 504 ± 91 g m⁻². Overall, the oxbow lake resulted net heterotrophic with plant and microbial respiration largely exceeding carbon fixation by photosynthesis. The water chestnut stand was a net sink of CO₂ during the day-light period (−60.5 ± 8.5 mmol m⁻² d⁻¹) but it was a net source at night (207.6 ± 6.1 mmol m⁻² d⁻¹), when the greatest CO₂ efflux rate was measured across the water surface (28.2 ± 2.4 mmol m⁻² h⁻¹). The highest CH₄ effluxes (6.6 ± 1.8 mmol m⁻² h⁻¹) were determined in the T. natans stand during day-time, whilst CH₄ emissions across the plant-free water surface were greatest at night (6.8 ± 2.1 mmol m⁻² h⁻¹). Therefore, we assumed that the water chestnut enhanced methane delivery to the atmosphere. On a daily basis, the oxbow lake was a net source to the atmosphere of both CO₂ (147.1 ± 10.8 mmol m⁻² d⁻¹) and CH₄ (116.3 ± 8.0 mmol m⁻² d⁻¹).     

Quantification of the water,energy and carbon footprints of wastewater treatment plants in China considering a water–energy nexus perspective

Water and energy are closely connected and both are very important for human development. Wastewater treatment plants (WWTPs) are central to water–energy interactions as they consume energy to remove pollutants and thus reduce the human gray water footprint on the natural water environment. In this work, we quantified energy consumption in 9 different WWTPs in south China, with different treatment processes, objects, and capacities. The energy intensity in most of these WWTPs is in the range of 0.4–0.5 kWh/m³ in 2014. Footprint methodologies were used in this paper to provide insight into the environmental changes that result from WWTPs. A new indicator “gray water footprint reduction” is proposed based on the notion of gray water footprint to better assess the role of WWTPs in reducing human impacts on water resources. We find that higher capacity and appropriate technology of the WWTPs will result in higher gray water footprint reduction. On average, 6.78 m³ gray water footprint is reduced when 1 m³ domestic sewage is treated in WWTPs in China. 13.38 L freshwater are required to produce the 0.4 kWh electrical input needed for treating 1 m³ domestic wastewater, and 0.23 kg CO₂ is emitted during this process. The wastewater characteristics, treatment technologies as well as management systems have a major impact on the efficiency of energy utilization in reducing gray water footprint via these WWTPs. The additional climate impact associated with wastewater treatment should be considered in China due to the enormous annual wastewater discharge. Policy suggestions are provided based on results in this work and the features of China's energy and water distribution.     

Performance evaluation of constructed wetlands in a tropical region

Five emergent plant species were compared for their effectiveness in treating contaminants in a wetland system constructed on a military base in El Salvador. The system consisted of the subsurface flow (SSF), open water (OW) and free surface flow (SF) wetlands with a combined flow capacity of up to 151.4 m³ d^?1. Reliability and consistent performance in extreme conditions, such as those occurring during the tropical dry or wet seasons were important evaluation criteria. The discontinuous flow patterns typical of tropical climates necessitated the use of water balance calculations using climatic data such as rainfall and evapotranspiration. System characterization was achieved by computation of daily input and output mass loading rates for each individual constituent. Results suggest that Phragmites and Brachiaria were the most effective plants in SSF wetland. Brachiaria provided the added benefit of serving as a source of fodder and proved proficient, with N and P uptakes of 1.5–3.14% and 0.17–0.25% per dry plants’ biomass, respectively. Typha yielded the highest dry season removal efficiency within the SF (BOD₅: 80.78 ± 9.35%, COD: 65.18 ± 19.6%, TN: 58.59 ± 19.3%, oil and grease: 78.34 ± 10.55%, total dissolved phosphorus: 66.5 ± 20.7%). Phragmites–Typha treatment subset performed better year-round than either Thalia–Thalia or Brachiaria–Cyperus. Evaluated plants were capable of surviving and proliferating in extreme tropical climates.