Suspended Solids Loads Research Articles

Freshwater Molluscs as Bioindicator of Fe and Mn Contamination in Lematang River, South Sumatera, Indonesia

Heavy metal in river come mainly from naturally occurring geochemical materials. However, human activities has enhanced concentration of heavy metal such as coal mine in the case of pollution in Lematang River. The high suspended solid loads in the river can remove most soluble metals from the water and trapped them in the bottom sediment. Freshwater molluscs were collected 3 sampling site, Lahat (ST1) as reference site, and polluted rivers of West Merapi (ST2) and East Merapi (ST2). Freshwater molluscs were analysed for the heavy metal contents in tissue. Relationships of the heavy metal in sediment to the heavy metal content in molluscs was performed using SPSS 24. Thiara scabra was the most abundant taxa in sampling area. Concentration of Fe and Mn in sediment has no significant effect on the Fe content in mollusc tissues. Molluscs appeared to more sensitive to higher Mn content. This study did not clearly show molluscs as a bioaccumulator for metal. Nonetheless, Thiara scabra were common, abundant, easily sampled and it is a useful choice as bioindicator in Lematang river for future study.

Simulation of the hydrological and environmental effects of a sponge city based on MIKE FLOOD

Based on the pilot area of a sponge city in Northwest China, the MIKE FLOOD models of urban flood and nonpoint source pollution are established. The uncertainty analysis of model shows that such parameters as hydrological reduction factor, imperviousness, and decay constant have big influences on the total runoff, peak flow, and water quality. The measured data of the rainfall events 20160724 and 20160623 are used to calibrate and validate the model. The correlation coefficients (R 2 ) and Nash–Sutcliffe efficiency coefficient (Ens) are both over 0.65. The changes in urban rainwater runoff and water quality for different rainfall conditions under traditional development (TD) and low impact development (LID) modes are simulated. The results show that: (1) Compared with TD mode, for different rainfall conditions under LID mode, the reduction rates of overflow and the overload pipes are, respectively, 22.4–100 and 0–54.55% when the area proportion of LID measures is 17.76%. The total runoff reduction rate is 64.01–81.52%, the peak flow reduction rate is 0–69.09%, and the flood peak time is delayed by 0–48 min. (2) Compared with TD mode, after adding LID measures, the load reduction rates of total suspended solids (SS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) are increased by 19.20–68.71, 19.19–67.78, 18.72–60.91, and 19.89–68.75%, respectively. The effluent reduction rates of the event mean concentrations (EMCs) of SS, COD, TN, and TP are increased by 0.65–42.07, 0.65–40.34, 0.06–27.62, and 1.51–42.14%, respectively. (3) The LID measures have certain control on waterlogging situation, and the submerged area under different water depths and flooding durations are decreased by 11.11–100 and 32.23–100%, respectively. For 19.2 mm rainfall event, under the LID mode, the SS load reduction rate achieves 60%, and rainfall runoff is all assimilated without discharge and waterlogging phenomena. LID measures have a better control effect on water quality and water quantity of urban rainstorm runoff; however, the effect of LID measures will reduce with the increase in recurrence interval.

Management Practices Used in Agricultural Drainage Ditches to Reduce Gulf of Mexico Hypoxia.

Agricultural non-point sources of nutrients and sediments have caused eutrophication and other water quality issues in aquatic and marine ecosystems, such as the annual occurrence of hypoxia in the Gulf of Mexico. Management practices have been implemented adjacent to and in agricultural drainage ditches to promote their wetland characteristics and functions, including reduction of nitrogen, phosphorus, and sediment losses downstream. This review: (1) summarized studies examining changes in nutrient and total suspended solid concentrations and loads associated with management practices in drainage ditches (i.e., riser and slotted pipes, two-stage ditches, vegetated ditches, low-grade weirs, and organic carbon amendments) with emphasis on the Lower Mississippi Alluvial Valley, (2) quantified management system effects on nutrient and total suspended solid concentrations and loads and, (3) identified information gaps regarding water quality associated with these management practices and research needs in this area. In general, management practices used in drainage ditches at times reduced losses of total suspended solids, N, and P. However, management practices were often ineffective during storm events that were uncommon and intense in duration and volume, although these types of events could increase in frequency and intensity with climate change. Studies on combined effects of management practices on drainage ditch water quality, along with research towards improved nutrient and sediment reduction efficiency during intense storm events are urgently needed.

Particle deposition, resuspension and phosphorus accumulation in small constructed wetlands

To improve understanding of phosphorus (P) retention processes in small constructed wetlands (CWs), we analysed variations in sediment deposition and accumulation in four CWs on clay soils in east-central Sweden. Sediment deposition (in traps) generally exceeded the total suspended solids (TSS) load suggesting that resuspension and wetland base erosion were important. This was confirmed by quantification of particle accumulation (on plates) (1–23 kg m−2 year−1), which amounted to only 13–23% of trap deposition. Spatial mean P concentrations in accumulated sediment on plates (0.09–0.15%) were generally similar to temporal mean P concentrations of particles in water (0.11–0.15%). Deposition/accumulation was minor in one wetland with high hydraulic load (400 m year−1), suggesting that such small wetlands are not efficient as particle sinks. Economic support for CWs are given, but design and landscape position are here demonstrated to be important for effective P retention.

Physiological consequences of chronic exposure of rainbow trout (Oncorhynchus mykiss) to suspended solid load in recirculating aquaculture systems

High levels of suspended solids, especially fines, are widely regarded as harmful to fish, particularly in recirculating aquaculture systems (RAS) where accumulation of particles is likely. However, little is known about the consequences of chronic exposure to system-related particles on the stress-levels, well-being and health of fish. In this study, the chronic effects of suspended solids on the physiology and performance of rainbow trout were investigated over the growout period, uncoupled from other potentially confounding water parameters. Compared with fish in a control system with a total suspended solid (TSS) load of 3.9mg/L, fish in an otherwise comparable treatment system exposed to minimum particle concentrations of more than 30mg/L exhibited no observable difference in hematological variables (differential leukocyte count, RBC and WBC counts, hematocrit), gill histology, fin condition, or heat shock protein 70 concentrations in gill, liver, skin and head kidney tissues. Slight alterations in feeding behavior and a slight increase in bacterial load on fish and in system water were observed in the treatment RAS, but without any apparent effect on fish performance or health. Furthermore, no significant difference in mortality occurred. The absence of expected effects across a wide range of physiological criteria after long-term exposure suggests that suspended solid levels over 30mg/L are within the physiological tolerance of this species.

Stormwater solids removal characteristics of a catch basin insert using geotextile

Suspended solids in urban runoff have multiple adverse environmental impacts and create a wide range of water quality problems in receiving water bodies. Geotextile filtration systems inserted within catch basins have the potential to mitigate these effects, through flow attenuation and pollutant removal. This study modelled a catch basin in a column and assessed the hydraulic and solids removal characteristics of a new type of non-woven geotextile (NWG1) in the capture of solids from stormwater runoff. The new geotextile was compared with two others readily available on the market (NWG2, NWG3). Synthetic stormwater containing TSS (200mg/L) was used with two particle size distributions of 0–180μm (P1; D50:106μm) and 0–300μm (P2; D50:150μm). The results revealed that the desired stormwater TSS concentration (<30mg/L; ANZECC, 2000) could be achieved with a short ripening process (e.g., 1–2kg/m2 of suspended solids loading) for trials using the larger particle size distribution (P2). In addition, 36% more suspended solids were captured in trials using the soil with the larger range of particle sizes (P2) than for the soil with smaller particle sizes (P1). Geotextile fibre pattern appeared to have a significant influence on the TSS removal capacity. The NWG1 has higher permittivity than NWG3 but similar to NWG2. NWG1 could capture overall more TSS (which also resulted in earlier clogging) than NWG2 and NWG3 because of the special fibre structure of NWG1. The experimental data shows that these geotextiles may start to clog when the hydraulic conductivity reaches below 1.36×10−5m/s. The overall hydraulic performances of geotextiles showed that the NWG1 has better potential for use in CBIs because of its higher strength and multiple reuse capability.

Using the HSPF and SWMM Models in a High Pervious Watershed and Estimating Their Parameter Sensitivity

Models are necessary tools for watershed management. However, applying watershed models is time consuming and requires technical knowledge, including model selection and validation. The objective of this study is to assess two commonly used watershed models and their parameter sensitivity to reduce model loadings and to gain a better understanding of the model performances. The Hydrological Simulation Program-Fortran (HSPF) model and Storm Water Management Model (SWMM) were applied to a mostly forested Taiwanese reservoir watershed with pollution from tea plantations. Statistical analysis showed that both models are suitable for the studied watershed, but the performances of the flow and water quality simulations are different. The mean flow simulated by SWMM was lower than the experimental observations. The HSPF model performed better, possibly because the soil in the study area is highly permeable and the HSPF model has more precise soil layer calculations. SWMM may underestimate the total phosphorous (TP) and suspended solid (SS) loads following small storm events in highly permeable watersheds. The Latin Hypercube-One factor At a Time (LH-OAT) method was used to determine the parameter sensitivity of the HSPF model and SWMM. In both of the models, the parameters related to infiltration and soil characteristics strongly affected the flow simulation, except when using the Horton infiltration method in the SWMM. Manning’s roughness coefficient for pervious areas was more sensitive in SWMM than in the HSPF model because SWMM has fewer parameters.

Does clogging affect long-term removal of organics and suspended solids in gravel-based horizontal subsurface flow constructed wetlands?

Constructed wetlands with horizontal subsurface flow (HF CWs) are primarily designed to remove organics and suspended solids. The major principle of this treatment process is that wastewater flows through the porous medium planted with wetland vegetation in order to achieve removal of pollutants. During the process the void spaces in the filtration material are slowly filled due to sedimentation and filtration of suspended solids, creation of biofilms on filtration material particles, chemical precipitation and growth of roots and rhizomes of the vegetation. Therefore, the clogging process is inevitable. However, the use of suitable porous filtration materials, responsible maintenance of pretreatment units and suitable loadings of organics and suspended solids may greatly slow down the clogging process. The purpose of this study was to evaluate the effect of partial ponding on treatment performance of four HF CWs that have been in operation for at least 20years. The results revealed that if the inflow loading rates are <10gBOD5m−2d−1, <20gCODm−2d−1, <10gTSSm−2d−1, the partial ponding may occur after about 15years of operation. The results also revealed that partial ponding have no significant effect on the quality of discharged water and the replacement of inflow zone filtration material did not results in any significant improvement either.

Optimization of Operation and Backwashing Condition for an Upflow Stormwater Filtration System Utilizing Ceramic Media

Stormwater filtration is widely used for the urban runoff treatment. However, intensive maintenance and lack of information about the performance have resulted in an increased need of proper evaluation. In this study, the performance of an upflow stormwater runoff filtration system, consisting of a supporting unit and a filtration unit filled with a ceramic media, was investigated. The maximum head loss increase was about 3 cm under the suspended solid (SS) load of 30 kg/m2 and the SS removal was more than 96%, when the filtration velocity was 20-40 m/h. The head loss and the porosity of the media can successfully be described by a power model. It was confirmed that the a significant amount of SS can effectively be removed at supporting unit, minimizing SS load to the filter media bed. Several backwashing strategies have been tested to establish the optimum condition. It was found that the stagnant water discharge is important to minimize the SS release immediately after backwashing. Also, the filter bed loaded with 400-450 kg/m2 SS can almost completely be washed to reduce the head loss to the that of empty bed. The results in this study indicate that the upflow ceramic media filter is an excellent alternative to stormwater treatment, with high SS removal and long lifespan. Key words: Non-Point Source Pollution, Stormwater Runoff, Upflow Filtration System, Backwash

Optimization of storage tank locations in an urban stormwater drainage system using a two-stage approach

Storage is important for flood mitigation and non-point source pollution control. However, to seek a cost-effective design scheme for storage tanks is very complex. This paper presents a two-stage optimization framework to find an optimal scheme for storage tanks using storm water management model (SWMM). The objectives are to minimize flooding, total suspended solids (TSS) load and storage cost. The framework includes two modules: (i) the analytical module, which evaluates and ranks the flooding nodes with the analytic hierarchy process (AHP) using two indicators (flood depth and flood duration), and then obtains the preliminary scheme by calculating two efficiency indicators (flood reduction efficiency and TSS reduction efficiency); (ii) the iteration module, which obtains an optimal scheme using a generalized pattern search (GPS) method based on the preliminary scheme generated by the analytical module. The proposed approach was applied to a catchment in CZ city, China, to test its capability in choosing design alternatives. Different rainfall scenarios are considered to test its robustness. The results demonstrate that the optimal framework is feasible, and the optimization is fast based on the preliminary scheme. The optimized scheme is better than the preliminary scheme for reducing runoff and pollutant loads under a given storage cost. The multi-objective optimization framework presented in this paper may be useful in finding the best scheme of storage tanks or low impact development (LID) controls.

Impact of satellite imagery spatial resolution on land use classification accuracy and modeled water quality

AbstractRemote sensing offers an increasingly wide array of imagery with a broad variety of spectral and spatial resolution, but there are relatively few comparisons of how different sources of data impact the accuracy, cost, and utility of analyses. We evaluated the impact of satellite image spatial resolution (1 m from Digital Globe; 30 m from Landsat) on land use classification via ArcGIS Feature Analyst, and on total suspended solids (TSS) load estimates from the Soil and Water Assessment Tool (SWAT) for the Camboriú watershed in Southeastern Brazil. We independently calibrated SWAT models, using both land use map resolutions and short‐term daily streamflow (discharge) and TSS load data from local gauge stations. We then compared the predicted TSS loads with monitoring data outside the model training period. We also estimated the cost difference for land use classification and SWAT model construction and calibration at these two resolutions. Finally, we assessed the value of information (VOI) of the higher‐resolution imagery in estimating the cost‐effectiveness of watershed conservation in reducing TSS at the municipal water supply intake. Land use classification accuracy was 82.3% for 1 m data and 75.1% for 30 m data. We found that models using 1 m data better predicted both annual and peak TSS loads in the full study area, though the 30 m model did better in a sub‐watershed. However, the 1 m data incurred considerably higher costs relative to the 30 m data ($7000 for imagery, plus additional analyst time). Importantly, the choice of spatial resolution affected the estimated return on investment (ROI) in watershed conservation for the municipal water company that finances much of this conservation, although it is unlikely that this would have affected the company's decision to invest in the program. We conclude by identifying key criteria to assist in choosing an appropriate spatial resolution for different contexts.

Contributions of combined sewer overflows and treated effluents to the bacterial load released into a coastal area

The impact of combined sewer overflow (CSO) on the receiving water body is an issue of increasing concern, as it may lead to restrictions in the use and destination of the receiving body, such as bathing or recreational area closures, fish and shellfish consumption restrictions, and contamination of drinking water resources. Recent investigations have mainly referred to the occurrence and loads of suspended solids, organic compounds and, in some cases, micropollutants. Attempts have been made to find correlations between the discharged load and the size and characteristics of the catchment area, climate conditions, rainfall duration and intensity.This study refers to a touristic coastal area in the north-east of Italy, which is characterized by a combined sewer network including 5 CSO outfalls which, in the case of heavy rain events, directly discharge the exceeding water flow rate into channels which, after a short distance, reach the Adriatic Sea. The study analyzed: i) rainfall events during the summer period in 2014 which led to overflow in the different outfalls, ii) the inter- and intra-event variability with regard to E. coli, Enterococci and conductivity, and iii) the hydraulic and pollutant (E. coli and Enterococci) loads discharged by the local wastewater treatment plant and by all the CSO outfalls. Finally, it estimated the contribution of each source to the released hydraulic and pollutant loads into the receiving water body. Moreover, it was also found that the modest water volume discharged by all CSO outfalls (only 8% of the total volume discharged by the area) contains >90% of the microbial load.

Greywater characterization and loadings – Physicochemical treatment to promote onsite reuse

Greywater is the wastewater produced in bathtubs, showers, hand basins, kitchen sinks, dishwashers and laundry machines. Segregation of greywater and blackwater and on site greywater treatment in order to promote its reuse for toilet flushing and/or garden irrigation is an interesting option especially in water deficient areas. The objective of this study was to characterize the different greywater sources in Greek households and to evaluate the performance of alternative physicochemical treatment systems to treat several types of greywater. Based on the results average daily greywater production was equal to 98 L per person per day and accounts for approximately 70–75% of the total household wastewater production (135 L per person per day). Among the different sources, laundry and kitchen sink are the main contributors to the total greywater load of organic carbon, suspended solids and surfactants, whereas dishwasher and bathroom greywater are the main sources of phosphorus and endocrine disrupting chemicals respectively. Depending on sources, greywater accounts for as low as 15% of the total wastewater load of organic carbon (in the case of light greywater sources), to as high as 74% of the total load organic load (in the case of the heavy greywater sources). On the other hand, the nutrients load of greywater is limited. The application of a physical treatment system consisting of coagulation, sedimentation, sand filtration, granular activated carbon filtration and disinfection can provide for a final effluent with high quality characteristics for onsite reuse, especially when treating light greywater.

Phytoremediation Capabilities of Spirodela polyrhiza and Salvinia molesta in Fish Farm Wastewater: A Preliminary Study

Fish farm wastewater needs to be treated as it contains considerably high loading of suspended solids and dissolved nutrients from accumulation of by-products e.g. fish excretions and uneaten feed. In this study, macrophytes, namely Spirodela polyrhiza and Salvinia molesta were examined for their phytoremediation efficiency in treating fish farm wastewater in a raceway pond rig. It was carried out indoor for 14 days under controlled environment. Water samples was collected once every 2 days for analysis of NO3-- N, PO43-, NH3-N, COD, turbidity, MLVSS and pH. The results showed that there was decrement of phosphate in fish farm wastewater using either S. polyrhiza or S. molesta. Interestingly, S. polyrhiza was found to be more efficient in phosphate uptake as it removed 72% phosphate at day 4 and up to 95% in the end of the experiment whereas 72% phosphate removal was only achieved by S. molesta at day 10. Similar ammonia decrement was observed for both plants and most of the ammonia were not detected in the wastewater by day 10 for S. polyrhiza, while by day 8 for S. molesta. Nitrate showed increment for both plants which could be due to nitrification. Both plants achieved highest COD removal on day 12, whereby 68% for S. polyrhiza and 63% for S. molesta. They were able to reduce turbidity and total suspended solids (TSS) to very low level and significantly increase clarity of wastewater. S. polyrhiza reduced up to 96% of initial turbidity value and 86% of TSS. 82% reduction of initial turbidity and 79% TSS decrement were observed for S. molesta. pH fluctuations were minimum for both plants, with a range between 7.62 to 7.77. Both plants demonstrated biomass increment for fresh weight in which 84% for S. polyrhiza while 85% for S. molesta. This study proved that the macrophytes were able to treat fish farm wastewater by significantly removing phosphate, ammonia, turbidity and TSS. It aids in minimizing pollutants released to receiving waters and producing biomass which can be utilized for agriculture sector.

An urban observatory for quantifying phosphorus and suspended solid loads in combined natural and stormwater conveyances

Water quality in urban streams and stormwater systems is highly dynamic, both spatially and temporally, and can change drastically during storm events. Infrequent grab samples commonly collected for estimating pollutant loadings are insufficient to characterize water quality in many urban water systems. In situ water quality measurements are being used as surrogates for continuous pollutant load estimates; however, relatively few studies have tested the validity of surrogate indicators in urban stormwater conveyances. In this paper, we describe an observatory aimed at demonstrating the infrastructure required for surrogate monitoring in urban water systems and for capturing the dynamic behavior of stormwater-driven pollutant loads. We describe the instrumentation of multiple, autonomous water quality and quantity monitoring sites within an urban observatory. We also describe smart and adaptive sampling procedures implemented to improve data collection for developing surrogate relationships and for capturing the temporal and spatial variability of pollutant loading events in urban watersheds. Results show that the observatory is able to capture short-duration storm events within multiple catchments and, through inter-site communication, sampling efforts can be synchronized across multiple monitoring sites.

SEDIMENTASI DI DELTA SUNGAI CITARUM, KECAMATAN MUARA GEMBONG, KABUPATEN BEKASI (Sedimentation at delta of Citarum River, Muara Gembong District, Bekasi Regency)

One of land use change impacts in the downstream of Citarum watershed is sedimentation. This study aimed to determine the total suspended solid and sediment load in the downstream of Citarum River. The Total Suspended Solid ( TSS ) samples were taken in three locations: the inlet of Jatiluhur reservoir, the outlet of Jatiluhur reservoir, and before the Citarum River estuary. The frequency of TSS samplings was twice a year i.e during the dry season and the rainy season at 2014. Analysis of TSS content was in accordance with SNI 06-6989.3-2004 using gravimetry method. The results showed that TSS at down stream Citarum River flow was 0.44 kg/m 3 , TSS at the inlet of Jatiluhur reservoir was 0.20 kg/m 3 , and TSS at the outlet of Jatiluhur reservoir was 0.02kg/m 3 . The total sediment in the inlet of Jatiluhur was 1.34 x 10 6 ton/year, in the outlet of Jatiluhur reservoir was 0.14 x 10 6 ton/year, and the flow sediment total to the Citarum River estuary was 1.79 x 10 6 ton/year. The Jatiluhur reservoir could reduce the potential for sediment total flowing into the sea as much as 1.20x 10 6 tons/year. Area of sedimentation at the delta of Citarum River was 3,828.26 ha.

Modelling and optimization of land use/land cover change in a developing urban catchment.

The impacts of land use/cover change (LUCC) on hydrological processes and water resources are mainly reflected in changes in runoff and pollutant variations. Low impact development (LID) technology is utilized as an effective strategy to control urban stormwater runoff and pollution in the urban catchment. In this study, the impact of LUCC on runoff and pollutants in an urbanizing catchment of Guang-Ming New District in Shenzhen, China, were quantified using a dynamic rainfall-runoff model with the EPA Storm Water Management Model (SWMM). Based on the simulations and observations, the main objectives of this study were: (1) to evaluate the catchment runoff and pollutant variations with LUCC, (2) to select and optimize the appropriate layout of LID in a planning scenario for reducing the growth of runoff and pollutants under LUCC, (3) to assess the optimal planning schemes for land use/cover. The results showed that compared to 2013, the runoff volume, peak flow and pollution load of suspended solids (SS), and chemical oxygen demand increased by 35.1%, 33.6% and 248.5%, and 54.5% respectively in a traditional planning scenario. The assessment result of optimal planning of land use showed that annual rainfall control of land use for an optimal planning scenario with LID technology was 65%, and SS pollutant load reduction efficiency 65.6%.

Influence of Cattle Trails on Runoff Quantity and Quality.

Cattle trails in grazed pastures close to rivers may adversely affect surface water quality of the adjacent river by directing runoff to it. The objective of this 3-yr study (2013-2015) in southern Alberta, Canada, was to determine if cattle trails significantly increased the risk of runoff and contaminants (sediment, nutrients) compared with the adjacent grazed pasture (control). A portable rainfall simulator was used to generate artificial rainfall (140 mm h) and runoff. The runoff properties measured were time to runoff and initial abstraction (infiltration), total runoff depth and average runoff rates, as well as concentrations and mass loads of sediment, N, and P fractions. Cattle trails significantly ( ≤ 0.10) decreased time to runoff and initial abstraction (26-32%) in the 2 yr measured and increased total runoff depth, runoff coefficients, and average runoff rates (21-51%) in 2 of 3 yr. Concentrations of sediment, N, and P fractions in runoff were not significantly greater for cattle trails than for control areas. However, mass loads of total suspended solids (57-85% increase), NH-N (31-90%), and dissolved reactive P (DRP) (30-92%) were significantly greater because of increased runoff volumes. Overall, runoff quantity and loads of sediment, NH-N, and DRP were greater for cattle trails compared with the adjacent grazed pasture, and hydrologic connection with cattle-access sites on the riverbank suggests that this could adversely affect water quality in the adjacent river. Extrapolation of the study results should be tempered by the specific conditions represented by this rainfall simulation study.

Field campaign on sediment transport behaviour in a pressure main from pumping station to wastewater treatment plant in Berlin.

As part of the project KURAS, the Berliner Wasserbetriebe realized a field campaign in 2015 in order to increase the process knowledge regarding the behaviour of transported sediment in the pressure main leading from the pumpstation to the wastewater treatment plant. The field campaign was conducted because of a lack of knowledge about the general condition of the pressure main due to its bad accessibility and the suspicion of deposits caused by hydraulic underload. The practical evidence of the sediment transport performance of this part of the sewer system, dependent on different load cases, should present a basis for further analysis, for example regarding flushing measures. A positive side-effect of the investigation was the description of the amount of pollutants caused by different weather conditions in combined sewer systems and the alterations of the sewage composition due to biogenic processes during transport. The concept included the parallel sampling of the inflow at the pumpstation and the outflow at the end of the pressure main during different weather conditions. By calculating the inflow to the pressure main, as well as its outflow at different flow conditions, it was possible to draw conclusions in regard to the transport behaviour of sediment and the bioprocesses within an 8.5 km section of the pressure main. The results show clearly that the effects of sedimentation and remobilization depend on the flow conditions. The balance of the total suspended solids (TSS) load during daily variations in dry weather shows that the remobilization effect during the run-off peak is not able to compensate for the period of sedimentation happening during the low flow at night. Based on the data for dry weather, an average of 238 kg of TSS deposits in the pressure main remains per day. The remobilization of sediment occurs only due to the abruptly increased delivery rates caused by precipitation events. These high pollution loads lead to a sudden strain at the wastewater treatment plant. It was found that the sediment transport behaviour is characterized by sedimentation up to a flow velocity of 0.35 m/s, while remobilization effects occur above 0.5 m/s. The assumption of bad sediment transport performance in the pressure main was confirmed. Therefore, the results can be used as a basis for further analysis, for example regarding periodical flushing as a means of cleaning the pressure main. The findings, especially regarding the methods and processes, are transferable and can be applied to other pressure mains in combined sewer systems. Besides the outlined evaluation of the sediment transport behaviour of the pressure main, the collected data were used in the project to calibrate a sewer system model, including a water quality model for the catchment area, and as a contribution towards an early physically based sediment transport modelling in InfoWorks CS.

Use of Satellite and In Situ Reflectance Data for Lake Water Color Characterization in the Everest Himalayan Region

This study applied remote sensing techniques to the study of water color in Himalayan glacial lakes as a proxy of suspended solid load. In situ measurements gathered in 5 lakes in October 2014 during satellite data acquisition enabled the characterization of water reflectance and clarity and supported image processing. Field data analysis led to a distinction between 3 water colors and a consequent lake water color classification on a regional scale from Landsat-8 data previously corrected for atmospheric and adjacency effects. Several morphometric parameters (lake size and shape, distance between lake and glacier) were also computed for the lakes thus classified. The results showed spatial and temporal variations in lake water color, suggestive of relationships between glacier shrinkage and the presence of brighter and more turbid water. A finer-scale analysis of the spatial variability of water reflectance on Chola Lake (based on GeoEye-1 data captured on 18 October 2014) showed the contribution of water component absorption from the inflow. Overall, the findings support further research to monitor Himalayan lakes using both Landsat-8 and Sentinel-2 (with its improved resolutions).