Water Quality Loads Research Articles

Improving water quality modelling for green roof runoff using Storm Water Management Model

Modelling of green roof is important for assessing its effectiveness as a low impact development (LID) practice. This study evaluated the performance of Storm Water Management Model (SWMM)’s LID Controls for modelling runoff water quality load from a green roof in Portland, Oregon, USA, for possible improvement. Such an attempt has been made rarely, although plenty of studies have evaluated SWMM's LID Controls for predicting green roof runoff. From the evaluation, the applicability of the SWMM for evaluating water quality such as total phosphorous (TP) and total nitrogen (TN) was “not satisfactory”. Nash-Sutcliffe Efficiency (NSE) value was 0.27 for TN and −1.45 for TP when using “rain concentration”, the only parameter available for water quality simulation of green roof runoff. The applicability was improved to “very good” level for TP with an NSE value of 0.66 when buildup and washoff were made possible by creating an imaginary twin subcatchment of the same size as the original one. However, NSE value for TN was not improved. The value of the work is that it could lead to a more accurate green roof design by minimizing pollutant release with improved prediction technology for TP.

Water Quality and Heavy Metal Load in Water and Sediments of Behlol Nullah, a Tributary of River Tawi, Jammu (J & K), India

Behlol nullah is an important tributary of river Tawi and its water quality is the major cause of concern because it receives untreated sewage as well as industrial waste from Gangyal and Bari Brahamana industrial complexes. A current effort is underway to examine the water quality and heavy metal load in the water and sediments. With various anthropogenic activities in mind, this water body has been divided into three stations namely Station-I, Station II and Station III, where Station I receives industrial effluents directly from Gangyal industrial area through Gadigarh nullah, Station II is situated downstream about 400 metres away from the site where industrial waste is directly drained into the nullah and station III is located at chatha around 6.6 kilometres away from station II and this station is devoid of any anthropogenic impacts. Standard procedures were used to analyse physicochemical parameters such as air temperature, water temperature, pH, DO, FCO2, Carbonates, Bicarbonates, Chlorides, Calcium, Magnesium, BOD, Nitrates, Phosphates and Sulphates in both water and sediments. Based on WQI score, the results of this investigation revealed variances in water quality. AAS was used to assess the level of pollution in the water and sediments of Behlol nullah for the heavy metals Fe, Cu, Zn and Pb. Heavy metal concentrations in sediments were found to be greater than in water, with the sequence of Fe>Zn>Cu>Pb in water and Fe>Cu>Zn>Pb in sediments. However, Fe was found to be highest in both water and sediments at all the study sites, and some heavy metal concentrations was found to be beyond the WHO- recommended tolerable level, indicating that this water body needs immediate attention.

Modeling for Mitigating Storm Water Unban Flooding and Water Quality Issues by Using Small Serial Dams: A Case Study of the City of San Angelo

<p>The City of San Angelo has been imposed on urban flooding and no-point source pollution and develop storm water monitoring and modeling project for managing these storm water issues. This study focuses on the stormwater peak flow reduction and water pollutant improvement by using small serial retention structures. The storm water data collected are utilized to verify storm water and event mean concentration in SWMM model. The verified SWMM that has range from 0.6 to 0.8 of coefficient of determination is modeled to evaluate small serial dams for reducing peak flow and water quality loading. Small serial dams explain the 26%~55.3% peak flow reduction and 53.2%~93.7% water pollutant removal percent. Sensitivity analysis results for three kinds of orifice sizes provide that smaller size increases the hydraulic retention and reduces the peak flow than other bigger size while the bigger size shows effective water pollutant reduction than small size.</p>

Seasonal variation in water quality, plankton diversity and microbial load of tropical freshwater lakes in Nigeria

Seasonal changes significantly affect tropical ecosystems; hence, verification of how these changes affect water quality is important for waterbodies that serve as water and food sources, particular as such changes are often associated with shifts in plankton diversity and microbial loads. This study assessed the seasonal changes in water quality, plankton diversity and microbial load in four lakes serving as sources of drinking water. Temperature, hardness and phosphate concentration were elevated in the dry season, and pH, biochemical oxygen demand, transparency, turbidity, total dissolved solids, conductivity, alkalinity and nitrate concentrations were elevated in the wet season. A phytoplankton analysis revealed that Chlorophyta, Bacillariophyta, Cyanophyta and Dinophyta were most common, with the families Desmidiaceae, Microcystaceae and Euglenaceae (phylum Euglenophyta) displaying dominance. For zooplankton, Rotifera was most common, with Branchionidae dominating the lakes in both seasons. In the wet season, Chlorophyta, Cyanophyta, Bacillariophyta and Dinophyta dominated, with Aphanizomenonaceae and Microcystaceae the most diverse families. Disease-causing pathogens, Ascaridae, Trichuridae and Ancylostomatidae (phylum Nematoda), were detected during periods of high rainfall. The waters in the dry season had higher microbial loads than in the wet season, ranging from 1.50 to 233.50 CFU g−1 (p < 0.05). This demonstrates the seasonal variations in risk to users and underlies the importance of regular assessment of water quality particularly given the threat of seasonal changes elated to climate change.

Smart Nutrient Retention Networks: a novel approach for nutrient conservation through water quality management

ABSTRACT Nutrients are essential resources for food production but are used inefficiently, and thereby they pollute inland and coastal waters and are lost into the oceans. Nutrient conservation by retention and consecutive reuse would prevent nutrient losses to the atmosphere and downstream ecosystems. We present Smart Nutrient Retention Networks (SNRNs) as a novel management approach to achieve nutrient conservation across networks of connected waterbodies through strategic water quality management. To present the key features of SNRNs, we review existing knowledge of nutrient retention processes in inland waters, water quality management options for nutrient conservation, and nutrient retention models to develop SNRNs. We argue that successful nutrient conservation, even at a local level, through SNRN management strategies requires clearly formulated goals and catchment-wide system understanding. Waterbody characteristics, such as hydraulic residence time and the presence of macrophytes, shape local nutrient retention with potential network-wide cascading effects of improved water quality and are therefore key targets of SNRN management strategies. Nutrient retention models that include the self-reinforcing feedback loop of ecological water quality, nutrient retention, and nutrient loading in networks of inland waters in relation to management options can support the development of SNRNs. We conclude that SNRNs can contribute to sustainable use of nutrients in human food production.

Effectiveness of environmental management institutions in sustainable water resources management in the upper Hanjiang River basin

The Han River valley plays an important strategic role in the water resources allocation system in China. A parallel hybrid approach was used in the study, using both qualitative and quantitative data collection and analysis techniques. Twenty self-administered questionnaires were sent to the heads of the environment bureaus of 17 districts (counties) and 3 cadres of the natural resources bureaus. Three in-depth interviews were conducted with the head of the water authority in the basin. Runoff, water quality and sediment load data were collected over a 17-year period and trends were analyzed using Mann-Kendall and regression analysis statistics to predict future water levels. The results show that the positive linear correlation between runoff R and sediment load is R2 = 0.1718, while the negative linear correlation between sediment load and pH value is R2 = 0.0329. According to the Mann-Kendall analysis(p &gt; 0.05) , no statistically significant trend was found in the data. The study concluded that there was a lack of effective regular interaction and cooperation between water and environmental management at the basin level. Effective Coordination of environmental management remains key to achieving sustainable water resources management in the Han River River Basin.

Evaluation of the predictive reliability of a new watershed health assessment method using the SWAT model.

The purpose of watershed assessments is to give information about conditions of water quality, stream morphology, and biological integrity to identify the sources of stressors and their impacts. In recent decades, different watershed assessment methods have been developed to evaluate the cumulative impacts of human activities on watershed health and the condition of aquatic systems. In the current research, we propose a new approach for assessing watershed vulnerability to contamination based on spatial analysis by using geographic information systems (GIS) and the analytic hierarchy process (AHP) technique. This new procedure, designed to identify vulnerable zones, depends on six basic factors that represent watershed characteristics: land use/land cover, soil type, average annual precipitation, slope, depth to groundwater, and bedrock type. The general assumptions for assessing watershed vulnerability are based on the response of watersheds to different contamination impacts and how the six selected factors interact to affect watershed health. The new watershed vulnerability assessment technique was used to create maps showing the relative vulnerabilities of specific sub-watersheds in the Eagle Creek Watershed in central Indiana. The results showed a remarkable difference in watershed susceptibility between the sub-watersheds in their vulnerability to pollution. To test the reliability of the proposed vulnerability assessment technique, the SWAT (Soil and Water Assessment Tool) model was applied to predict the water quality in each sub-watershed. Using the SWAT model, some parameters (e.g., total suspended solids [TSS] and nitrate) were tested based on the availability of the data needed for comparison. Both the SWAT and the newly proposed method produced good results in predicting water quality loads, which validated the proposed method. Hence, the results of the evaluation of the predictive reliability of the watershed vulnerability assessment method revealed that the proposed approach is suitable as a decision-making tool to predict watershed health.

Water quality and pollution loading of a river segment affected by landfill leachate and domestic waste

ABSTRACT The Marikina River in the Philippines has been polluted by Payatas landfill leachate, and domestic and agricultural waste. This study monitored the water quality at five stations on the river and two stations on two creeks that discharge to the river to determine the effects of Payatas landfill and to estimate pollution loading. The dissolved oxygen (DO), chemical oxygen demand (COD) and other water quality parameters were compared with the Philippines Standards for river water classification. It was found that Payatas leachate has a significant influence on the DO and COD levels as well as other water quality parameters. Per capita pollution loading for Quezon City was found to be lower than for Europe and Japan. The effect of leachate is more significant during the dry season. It is recommended that a leachate collection system be established to prevent leachate form entering Payatas creek, and that the Patayas landfill be replaced with a modern landfill site, conforming to current best practice at another location. List of Abbreviation: BOD= Biological Oxygen Demand COD = Chemical Oxygen Demand DO = Dissolved Oxygen EC = Electrical Conductivity M1, M2, M3, M4, M5 = monitoring stations TDS = Total Dissolved Solids TSS = Total Suspended Solids

Rice Drain Management to Reduce Seepage Exports in the Sacramento-San Joaquin Delta, California.

Many deltas worldwide face subsidence issues due to increased anthropogenic activity. The Sacramento-San Joaquin delta similarly faces ongoing subsidence, more than 8 m in some areas, that increases levee failure risks and threatens the security of this water source for 25 million California residents and 1.2 million ha of agriculture. Rice ( L.) fields are an integral part of a proposed new strategy for managing subsidence because they have been shown to stop subsidence and provide an alternative crop for growers. Two important considerations for implementing rice fields are additional water requirement and the effect on water quality from mobilized dissolved organic carbon (DOC) and disinfection byproduct precursors. To understand constituent transport and potential management opportunities for rice farming, a plug flow reactor mass balance model was used to quantify surface and subsurface hydrologic pathways. Management of adjacent drainage ditch water levels under low and high scenarios were tested as a strategy to reduce seepage and water quality loads. Under high drains, groundwater met 10% of evapotranspiration (ET). Low drains resulted in a 100% increase in ET demand, which was met by surface water applied for irrigation. High drains reduced subsurface seepage by 95%. Subsurface DOC, trihalomethane, and total dissolved nitrogen loads were reduced 10-fold in high drains compared with low drains. Flow rate accounted for 74 to 90% of load variance and was the primary determinant of constituent loads. Thoughtful implementation of rice cultivation, with high water levels in adjacent drains, can be leveraged to reduce irrigation water demand and constituent load outputs.

The Effect of Eco-Wetlands and Microbial Attached Vegetation Block on Water Quality in Ecological River Construction

This study evaluated the effects of installing eco-wetlands and microbial attached vegetation block in the Muhan river flowing into the Sapkyo river on water quality using the QUAL2E model. As a result of simulation after the construction of ecological river, water quality concentration at the joint point of the Sapkyo river was reduced by about 29.5% due to eco-wetlands (Case 1). It is also found that BOD changed by 31.6 - 69.6% when microbial attached vegetation block was also installed along with the eco-wetlands (Case 2). If only microbial attached vegetation block was installed, water quality concentration was reduced by about 18.4-39.5% (Case 3). The maximum reduction of water quality load on the downstream was found when microbial attached vegetation block was installed with eco-wetlands. In addition, when microbial attached vegetation block was installed, effluent purification effect turned out to be higher with a longer application distance than 500 m from the joint point with Yesan river.본 연구는 삽교천으로 유입되는 무한천의 생태하천 조성을 위해 인공습지와 미생물부착형 생태게비온의 적용효과를 검토하고자 실험과 하천지형분석을 통해 하천수질과 유량계수를 산출하고 이를 반영한 QUAL2E 수질모형을 구축함으로써 정확하고 합리적인 하천수질을 예측하였다. 무한천의 생태하천 조성으로 인한 하천수질변화를 예측한 결과, 인공습지로 인해 삽교천 합류지점의 수질농도가 현재와 비교하여 약 29.5% 저감할 수 있는 효과가 나타났다. 또한 미생물부착형 생태게비온을 함께 설치했을 경우 인공습지만 조성했을 때와 비교하여 BOD가 약 31.6-69.6 %로 하천수질이 변화되었다. 미생물부착형 생태게비온만 설치했을 경우 현재 수질상태보다 약 18.4-39.5 %의 저감할 수 있었다. 인공습지와 더불어 미생물부착형 생태게비온을 설치할 때 하류부의 수질부하를 최대한 저감시킬 수 있을 것으로 나타났다. 또한, 미생물부착형 생태게비온을 설치하였을 때 예산천 합류후 500m지점을 기준으로 그 적용구간이 길어질수록 하천정화효과가 높게 나타났다.

Assessing changes in surface water quality and pollutant load in Dong Nai province

This study aims at assessing changes in the surface water quality in Dong Nai province (2010- 2014). In addtion, the pollutant loads of wastewater sources were calculated till 2020–2030 with 03 wastewater treatment scenarios serving for the local environmental management. The water quality index (WQI) showed the surface water quality of Dong Nai Province to be gradually improved during the dry season but significantly declined in the rainy season in the last 5 years due to high concentrations of suspended solids (SS), Fe and microorganism - especially in the 3rd segment of Dong Nai river through Bien Hoa City. This current status certainly relates to pollutant loads from waste water sources in the province. Pollutant loads of domestic and industrial wastewater in Bien Hoa city are the highest (40 % per source), livestock activities in Xuan Loc district account for 20 %; aquaculture activities in Nhon Trach district contribute more than 75 % of the corresponding total loads, etc. in which loads of BOD5, COD and SS are significant, about 581,570 tons, 1,035,403 tons and 639,153 tons per year, respectively, and tend to increase in the future, requiring appropriate solutions.

Modeling Water-Quality Loads to the Reservoirs of the Upper Trinity River Basin, Texas, USA

The Upper Trinity River Basin (TRB) is the most populated river basin and one of the largest water suppliers in Texas. However, sediment and nutrient loads are reducing the capacity of reservoirs and degrading water quality. The objectives of this study are to calibrate and validate the Soil and Water Assessment Tool (SWAT) model for ten study watersheds within the Upper TRB in order to assess nutrient loads into major reservoirs in the basin and to predict the effects of point source elimination and urbanization on nutrient loads through scenario analyses. SWAT performed reasonably well for the current condition except for two out of five tributaries in the Eagle Mountain watershed and total phosphorous OPEN ACCESS Water 2015, 7 5690 in Richland-Chambers. The impacts of simulated scenarios varied within watersheds. Point-source elimination achieved reductions ranging from 0.3% to 24% in total phosphorus and 1% to 56% in total nitrogen received by the reservoirs. Population and development projections were used to examine the impacts of urbanization on each watershed. Projected urbanization in 2030 had large effects on simulated total phosphorus loads in some watersheds, ranging from a reduction of 1% to an increase of 111%. Projected urbanization also affected simulated total nitrogen loads, from a reduction of 3% to an increase of 24%. One limitation of this study is the lack of long-term, up-to-date water quality data due to discontinued water-quality monitoring stations. Although careful considerations were given to the adjustment of parameter values reflecting various aspects of the nutrient processes, further data collection will enhance modeling study for assessment of these watersheds’ water resources and environmental problem.

Development of a decision-making methodology to design a water quality monitoring network

The number of water quality monitoring stations in the USA has decreased over the past few decades. Scarcity of observations can easily produce prediction uncertainty due to unreliable model calibration. An effective water quality monitoring network is important not only for model calibration and water quality prediction but also for resources management. Redundant or improperly located monitoring stations may cause increased monitoring costs without improvement to the understanding of water quality in watersheds. In this work, a decision-making methodology is proposed to design a water quality monitoring network by providing an adequate number of monitoring stations and their approximate locations at the eight-digit hydrologic unit codes (HUC8) scale. The proposed methodology is demonstrated for an example at the Upper Colorado River Basin (UCRB), where salinity is a serious concern. The level of monitoring redundancy or scarcity is defined by an index, station ratio (SR), which represents a monitoring density based on water quality load originated within a subbasin. By comparing the number of stations from a selected target SR with the available number of stations including the actual and the potential stations, the suggested number of stations in each subbasin was decided. If monitoring stations are primarily located in the low salinity loading subbasins, the average actual SR tends to increase, and vice versa. Results indicate that the spatial distribution of monitoring locations in 2011 is concentrated on low salinity loading subbasins, and therefore, additional monitoring is required for the high salinity loading subbasins. The proposed methodology shows that the SR is a simple and a practical indicator for monitoring density.

Runoff Characteristics of Nutrients from Agroforest Culture Field

본 연구에서는 최근 산림소득작물로 재배면적이 급증하고 있는 오미자를 대상으로 일반 농경지와 산림농업지에 시비된 식물영양성분의 행방과 유출부하량을 비교 평가하여 환경친화형 산림농업 시스템을 정착하는데 필요한 기초자료를 제공하고자 하였다. 표토 침식 및 식물영양물질의 유출에 더 민감함을 보여주는 지표로 활용되는 유출계수가 일반 농경지 시험구보다 산림농업시험구에서 더 높게 나타났다. 일반 농경지 시험구와 산림농업시험구에서 강우-유출에 의한 총질소와 총인의 유출부하량을 평가한 결과, 산림농업 시험구에서 식물영양성분의 손실로 인한 인근 수권 생태계에 끼치는 영향은 미미할 것으로 나타났다. 그러나, 산림농업을 위한 농경지 조성 초기에 식생으로 인한 토양피복도 부족과 토양구조 불안정으로 인행 상당량의 토사유출이 발생할 수 있는 것으로 나타났다. 따라서, 산림농업을 위한 농경지 조성 초기 단계에는 토양의 유실감수성을 고려한 테라스 및 승수로 등 토양유실 방지대책이 고려되어야 할 것이다.

Automating Online Reef Report Cards – Linking Land Management Practices to Water Quality and Coral Reef Ecosystem Health

This paper describes an online information management system (AORRA) that we are developing for the Great Barrier Reef Foundation (GBRF), in collaboration with State and Federal agencies in Australia, to automate the production and online publication of annual Reef Plan Report Cards. The Reef Water Quality Protection Plan is a collaborative program designed to improve the quality of water in the Great Barrier Reef through improved land management practices in reef catchments. The Reef Plan sets ambitious but achievable targets for water quality and land management improvements, and identifies actions to improve the quality of water entering the reef. The success of the plan is measured through Paddock to Reef and Marine Monitoring Programs and annual Reef Plan Report Cards that integrate information and report on land management practices, catchment indicators, water quality loads and the health of the Great Barrier Reef. This paper describes the technical challenges we faced in developing AORRA (Automated Online Reef Reporting Application) – including the integration of heterogeneous monitoring datasets, the derivation of meaningful indicators and the generation of report card products that data about complex spatio-temporal environmental processes to a non-technical audience.

A hydrological and nutrient load balance for the Lake Clearwater catchment, Canterbury, New Zealand

Nitrogen and phosphorus entering waterways from diffuse agricultural sources is a major problem in New Zealand and internationally. This problem is well documented for lowland areas but little is known about nutrient enrichment from farming in high country areas. The Lake Clearwater catchment, in the Canterbury high country of New Zealand, has a native ecosystem that has adapted to low-nutrient conditions. The Department of Conservation's Arawai Kakariki Wetland Restoration Programme identifies wetlands in the catchment as one of three key endemic wetland types. Uncertainty regarding diffuse nutrient load from agriculture into the lake and wetland is limiting effective management of this unique catchment. This study investigated the hydrological regimes and nitrogen and phosphorus concentrations and loads in five key surface waterways at ten surface water sites and three groundwater seeps for two years. It aims to improve knowledge of nutrient sources, characteristics and loads from agricultural land use in this 46 km2 high country catchment. Additionally, nutrient load predictions from the Catchment Land Use for Environmental Sustainability (CLUES) model were compared to measured nutrient loads to assess the applicability of the model in high country catchments. The CLUES model was developed, primarily for lowland areas, to predict changes in water quality and nutrient loads from land-use change. The total nitrogen concentrations downstream of farmland were typically above the Australia and New Zealand Environment and Conservation Council (ANZECC) water quality guideline and the median concentration for upland Canterbury waterways. Specifically, the nitrate concentration (0.19-0.29 g m-3) in farmland subsurface runoff was elevated, compared to streams in the Lake Clearwater catchment with unfarmed catchments, and was estimated to contribute 52% of total nitrogen yield from farmland. The total nitrogen yield (1.96-2.94 kg ha-1 year-1) for farmed land was comparable to minimum values for New Zealand pastoral land use reported in the literature. The total estimated nitrogen export from Lake Clearwater (2518 kg year-1) was 83% greater than the estimated diffuse input from all land in the catchment (1375 kg year-1). This indicated an additional source of nitrogen into the lake and seasonal nitrogen saturation. Total phosphorus yields (0.093-0.123 kg ha-1 year-1) downstream of farmland were well below yields for New Zealand pastoral land use reported in the literature. Total estimated phosphorus export from the lake (58 kg year-1) was 24% less than total estimated diffuse loads into the lake (76 kg year-1). The ratio of total nitrogen to total phosphorus in Lake Clearwater (49:1) indicated that phosphorus is the limiting nutrient and that nitrogen loads into the lake are above natural levels. Total nitrogen loads predicted by the CLUES model in the Lake Clearwater catchment were reasonable, providing land-use area inputs are accurate and nutrient loads exit catchments in surface water. However, CLUES greatly overestimated phosphorus loads from farmed and unfarmed land.

Rating Curve Estimation of Surface Water Quality Data Using LOADEST

Measurement of the nutrient concentrations in the stream is usually done on weekly, biweekly or monthly basis due to limited resources. There is need to estimate concentration and loads during the period when no data is available. The objectives of this study were to test the performance of a suite of regression models in predicting continuous water quality loading data and to determine systematic biases in the prediction. This study used the LOADEST model which includes several predefined regression models that specify the model form and complexity. Water quality data primarily nitrogen and phosphorus from five monitoring stations in the Neuse River Basin in North Carolina, USA were used in the development and analyses of rating curves. We found that LOADEST performed generally well in predicting loads and observation trends with general tendency/bias towards overestimation. Estimated Total Nitrogen (TN) varied from observation (“true” load) by -1% to 9%, but for the Total Phosphorus (TP) it ranged from -2% to 27%. Statistical evaluation using R2, Nash-Sutcliff Efficiency (NSE) and Partial Load Factor (PLF) showed a strong correlation in prediction.

Estimation of diffuse pollution loads in Europe for continental scale modelling of loads and in‐stream river water quality

AbstractAn export coefficient model of diffuse pollution at large scales has been developed as part of a larger study investigating and mapping the present and future patterns of the quantity and quality of European water resources. The model was developed to provide reasonable estimates across the whole of Europe based on readily accessible datasets, and that would be amenable to application within a gridded model of water quality loadings to surface waters. The export coefficient models for biochemical oxygen demand (BOD), total nitrogen (TN) and total phosphors (TP) were fitted to data from European Union European Environment Agency databases of 79–106 selected river basins around Europe depending on the variable in question. Estimated export coefficients were on a reasonable level with estimates made by other methods within Europe. Firstly, it was shown that runoff, number of livestock and point load were common factors for BOD, TP and TN loads with runoff as the most important factor. Secondly, cropland area also contributed to diffuse TN load. Thirdly, average slope steepness and runoff, as a combined factor, had a negative effect on diffuse TP load. Fourthly, lake area reduced diffuse loads because of retention mechanisms in lakes. A larger set of data with higher spatial and temporal resolution and partitioning of the data based on, e.g. climate or spatial patterns would further improve the precision of the export coefficient estimates. When applied at the catchment scale, the parameters should be updated with local data. In the long run, adaptive modelling should be applied in order to fit the model to continuously accumulating data and experience, although the study showed that the export coefficients derived were stable over time. It is also advisable to integrate the administrative monitoring, modelling and management of river basins more closely to improve data availability, model predictions and cost efficiency of management measures and policies. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Parameters affecting HS emissions removal and re-circulating water quality in a pilot-scale sequential biological treatment system at a wastewater lift station in Brownsville, Texas, USA

In this study, a pilot-scale sequential biological treatment system combining a biotrickling filter and biofilter was used to optimize the removal of variable emission H2S loadings ranging from 30 to 120 g m−3 h−1at a wastewater lift station in Brownsville, Texas USA. The biotrickling filter recycle water pH remained between 2.0 to 3.0 during the four months of unit operation and the overall removal efficiency for H2S was >99%. The biotrickling filter removal efficiency was 70 ± 8%, with an elimination capacity of 10 to 80 g m−3 h−1 while the biofilter elimination capacity ranged from 10 to 40 g m−3 h−1. The sequential treatment system was operated initially at an Empty Bed Residence Time (EBRT) of 120 s (50 s for the biotrickling filter and 70 s for biofilter) for two months and then at an EBRT of 60 s (25 s for biotrickling filter and 35s for biofilter) for the remainder of the operating period; remarkably, there was only a slight decrease in removal efficiency at 60 s EBRT. In order to qualitatively evaluate the changes in recycle water quality in the system on the performance of the unit in precipitating sulfur species, the equilibrium chemical model, Visual MINTEQ was employed. The model predicted speciation results based on the feed water quality and sulfur loadings, and also forecast some iron-sulfur complexes which have potential to form some complex precipitates. This research demonstrated that low pH re-circulating water quality in the biological treatment of H2S was possible without compromising the high removal efficiency, and that an improved understanding of the recycle water chemistry of the trickling unit of a sequential treatment system could be useful in the overall optimization of the process.

Technical Note: Assessing a 24/7 solution for monitoring water quality loads in small river catchments

Abstract. Quantifying nutrient and sediment loads in catchments is difficult owing to diffuse controls related to storm hydrology. Coarse sampling and interpolation methods are prone to very high uncertainties due to under-representation of high discharge, short duration events. Additionally, important low-flow processes such as diurnal signals linked to point source impacts are missed. Here we demonstrate a solution based on a time-integrated approach to sampling with a standard 24 bottle autosampler configured to take a sample every 7 h over a week according to a Plynlimon design. This is evaluated with a number of other sampling strategies using a two-year dataset of sub-hourly discharge and phosphorus concentration data. The 24/7 solution is shown to be among the least uncertain in estimating load (inter-quartile range: 96% to 110% of actual load in year 1 and 97% to 104% in year 2) due to the increased frequency raising the probability of sampling storm events and point source signals. The 24/7 solution would appear to be most parsimonious in terms of data coverage and certainty, process signal representation, potential laboratory commitment, technology requirements and the ability to be widely deployed in complex catchments.