High Water Turbidity Research Articles

유동흐름 전류계를 이용한 정수장 고탁도 유입수 응집 제어 방법에 대한 연구

Objectives: This study was aimed at determining the optimum coagulation dosage in a high turbid kaolin water sample using streaming current detection (SCD) as an alternative to the jar test. Methods: SCD is able to optimize coagulant dosing by titration of negatively charged particles. Kaolin particles were used to mimic highly turbid water ranging from 50 to 600 NTU, and polyaluminum chloride (PAC, 17%) was applied as a titrant and coagulant. The coagulation consisted of rapid stirring (5 min at 140 rpm), reduced stirring (20 min at 70 rpm), and settling (60 min). To confirm the coagulation effect, a jar test was also compared with the SCD titration results. Results: SCD titration of kaolin water samples showed that the dose of PAC increased as the pH rose. However, supernatant turbidity less than 1 NTU after coagulation was not achieved for high turbid water by SCD titration. Instead, a conversion factor was used to calculate the optimum PAC dosage for high turbid water by correlating a jar test result with that from an SCD titration. Using this approach, we were able to successfully achieve less than 1 NTU in treated water. Conclusions: For high turbid water influent in a water treatment plant, particularly during summer, the application of SCD control by applying a conversion factor can be more useful than a jar test due to the rapid calculation of coagulation dosage. Also, the interpolation of converted PAC dose could successfully achieve turbidity in the treated water of less than 1 NTU. This result indicates that an SCD system can be effectively used in a water treatment plant even for high turbid water during the rainy season.

Use of Moringa oleifera seed extracts to reduce helminth egg numbers and turbidity in irrigation water

Water from wastewater-polluted streams and dug-outs is the most commonly used water source for irrigation in urban farming in Ghana, but helminth parasite eggs in the water represent health risks when used for crop production. Conventional water treatment is expensive, requires advanced technology and often breaks down in less developed countries so low cost interventions are needed. Field and laboratory based trials were carried out in order to investigate the effect of the natural coagulant Moringa oleifera (MO) seed extracts in reducing helminh eggs and turbidity in irrigation water, turbid water, wastewater and tap water. In medium to high turbid water MO extracts were effective in reducing the number of helminth eggs by 94–99.5% to 1–2 eggs per litre and the turbidity to 7–11 NTU which is an 85–96% reduction. MO is readily available in many tropical countries and can be used by farmers to treat high turbid water for irrigation, however, additional improvements of water quality, e.g. by sand filtration, is suggested to meet the guideline value of ≤1 helminth egg per litre and a turbidity of ≤2 NTU as recommended by the World Health Organization and the U.S. Environmental Protection Agency for water intended for irrigation. A positive correlation was established between reduction in turbidity and helminth eggs in irrigation water, turbid water and wastewater treated with MO. This indicates that helminth eggs attach to suspended particles and/or flocs facilitated by MO in the water, and that turbidity and helminth eggs are reduced with the settling flocs. However, more experiments with water samples containing naturally occurring helminth eggs are needed to establish whether turbidity can be used as a proxy for helminth eggs.

Remote-sensing inversion model of surface water suspended sediment concentration based on in situ measured spectrum in Hangzhou Bay, China

Suspended sediment concentration (SSC) is an important parameter for monitoring coastal water quality. Suspended particles are also the main optically active substances for ocean color remote sensing. It is important to study the surface reflectance spectra features of coastal turbid water, as it can be the basis for establishing more accurate remote-sensing inversion models. In this study, Hangzhou Bay, China, was selected as the study area. Two in situ measurement and sampling stations in the estuary of the Qiantang River which flows into Hangzhou Bay were set up separately. Above-water spectrum observation method, which the NASA recommended, was adopted to measure the reflection spectrum of turbid waters. Surface water samples were simultaneously collected to obtain the corresponding SSC data. The results showed that the total suspended particle concentrations in the Hangzhou Bay were typically high, and the inorganic suspended particle concentrations were far greater than the phytoplankton concentrations, which averages 705 mg/L and 1.16 mg/m3. The SSC at two sampling stations both showed significant temporal variability, particularly appearing short-period rapid fluctuations accompanying the tidal cycle. The measured surface water reflectance spectra all showed typical curve characteristics of high turbid water, and as the SSC increased, the corresponding reflectivity of surface water also increased. The increments at different wavelengths were variational, with two reflectance peaks appearing at 650–700-nm and near the 800-nm wavelength of spectral curves, respectively. The first derivative of spectral curves showed that the first reflectance peak location appeared to be a “red shift” phenomenon with the SSC increasing. The correlation coefficients between the SSC of surface water and the remote-sensing reflectance according to moderate resolution imaging spectra-radiometer (MODIS) channels’ central wavelength were different significantly, which were larger at MODIS long-wavelength channels (>650 nm) and smaller at MODIS short-wavelength channels (400–550 nm). The value of determination coefficient R 2 was 0.82 when the reflectance ratio of MODIS band 2 to band 1 was selected as the SSC sensitive bands combination and exponential regression analysis was employed. Therefore, the reflectance ratio of MODIS band 2 to band 1 can be adopted as the main band combination for establishing surface water SSC remote-sensing inversion model in the Hangzhou Bay.

Hybrid process of coagulation/flocculation with Moringa oleifera followed by ultrafiltration to remove Microcystis sp. cells from water supply

Abstract In Brazil and other countries, the large biomass of monospecific crops and the need to enhance plant growth by the extensive use of fertilizers have caused a fast eutrophication of rivers and reservoirs that has resulted in a high growth in the population of cyanobacteria, of which several species have been described as producers of toxins capable of causing death of domestic and wild animals, in addition to problems to human health. The objective of the present work was then to evaluate the efficiency of Moringa oleifera seeds as coagulant in removing cells of the cyanobacterium Microcystis sp., apparent color, and turbidity from water in association with ultrafiltration. For the experiments, deionized water was artificially contaminated with Microcystis sp. cells from a culture. Mixing was carried out until samples with initial turbidity of 350 and 450 NTU were obtained to simulate high turbidity water with bloom of cyanobacteria. After being prepared, the samples were subjected to the processes of (1) coagulation/flocculation with moringa seeds (CFM), (2) UF, and (3) combined coagulation/flocculation with moringa solution followed by ultrafiltration (CFM-UF). The CFM process was carried out with a solution of 1% moringa seeds at concentrations of 25 to 300 mg/L. Mixing was promoted in a jar test device. Poly(ether sulfone) membrane with retention of 50 kDa and operating pressure of 2 bar was used for the UF process. In the CFM process, turbidity removal ranged from 49 to 97.4%, color removal varied between 39 and 99.2%, and removal of Microcystis sp. cells ranged from 20 to 91%. Applying the analysis of variance to the results, optimal moringa concentrations of 175 and 250 mg/L were obtained for water samples of 350 and 450 NTU respectively. These concentrations were used in the combined CFM-UF process. Microcystis sp. cells were not detected in treated water after UF and CFM-UF processes. Color and turbidity removal was above 99% for both processes. For the permeate flux, the combined CFM-UF process and the UF process alone presented average relative fluxes of 40% and 29.4%, respectively. Membrane fouling was 78.5% for UF and 70% for CFM-UF. This way, it can be said that coagulation/flocculation with moringa can be applied to high turbidity water, with high removal of color, turbidity, and Microcystis sp. cells, reaching more than 99% when this process was combined with ultrafiltration. In addition, the combined process showed higher permeate flux and slightly lower fouling percentage when compared with the UF process alone.

Simulation for Sludge Flocculation I: Brownian Dynamic Simulation for Perikinetic Flocculation of Charged Particle

To investigate sludge drying process, a numerical simulation based on Brownian dynamic for the floc with uncharged and charged particles was conducted. The Langevin equation is used as dynamical equation for tracking each particle in a floc. An initial condition and periodic boundary condition which well conformed to reality is used for calculating the floc growth process. Each cell consists of 1000 primary particles with diameter 0.1 ~ 4 μm. Floc growth is related to the thermal force and the electrostatic force. The electrostatic force on a particle in the simulation cell is considered as the sum of electrostatic forces from other particles in the original cell and its replicate cells. It is assumed that flocs are charged with precharged primary particles in dispersion system by ionization. By the analysis of the simulation figures, on one hand, the effects of initial particle size and sludge density on floc smashing time, floc radius of gyration, and fractal dimension were discussed. On the other hand, the effects of ionization on floc smashing time and floc structure were presented. This study has important practical value in the high‐turbidity water treatment, especially for sludge drying.

Paleoenvironmental conditions at Core KC01B (Ionian Sea) through MIS 13–9: Evidence from calcareous nannofossil assemblages

Quantitative analyses on calcareous nannofossil assemblages on high temporal resolution (600–800 years) have been carried out from Core KC01B in the Ionian Sea (Eastern Mediterranean) throughout Marine Isotope Stage (MIS) 13–9, between 500 and 300 ka. This is an interval of considerable climate changes, known as the Mid-Brunhes event, which includes MIS 11, considered as a possible analogue for future interglacial conditions. In the Mediterranean core, the interval is characterized by the dominance of Gephyrocapsa spp., as also known from ocean records. Calcareous nannofossil abundance fluctuations have been interpreted in terms of modification of sea surface primary productivity/water stratification and temperature. Specifically, the increase in abundance of Gephyrocapsa caribbeanica and small Gephyrocapsa coupled with decreases of Florisphaera profunda, Syracosphaera spp. and Rhabdosphaera spp. suggests enhanced primary productivity/mixed surface waters during interglacial stages and at the Terminations, which can be interpreted in terms of interaction between climate changes and mesoscale oceanographic circulation. On the other hand, distributions of Calciosolenia spp., Oolithotus spp. and Umbilicosphaera sibogae, which are in phase with δ18O curve showing higher abundances at the lighter values of the marine isotope record, are considered as warm-water indicators.Biotic proxies point to peculiar climate dynamics through the MIS 12–11 transition (i.e. Termination V). High productive, cool, low salinity and turbid surface waters characterize the early MIS 11 (421–408 ka) and likely reflect enhanced continental humidity/monsoon activity over North Africa and increased runoff into the basin. A late surface water warming with respect to Termination V is established at about 403 ka, during a period of low insolation forcing, almost coeval with the deposition of sapropel S11. A climate optimum, lasting about 15 ky (403–389 ka), is then recorded during a period of low insolation forcing centred at 398 ka. The later part of MIS 11 is characterized by climate deterioration at about 389 ka. Comparison with results from subtropical to polar Atlantic records suggests a remarkable relation between Mediterranean and Atlantic climate regimes.

Retrieval of Microcystis aentginosa Percentage From High Turbid and Eutrophia Inland Water: A Case Study in Taihu Lake

Microcystis aentginosa (MA), which is one kind of cyanobacteria, is the primary algal species in Taihu Lake. The MA bloom has a significantly negative effect on the human health and water environment ecosystem. The monitoring and prediction of MA bloom become more and more critical for the security of drinking water source and environment in the Taihu Lake area. In this paper, the percentage of MA was estimated from remote-sensing reflectance via a novel spectral shape genetic optimization algorithm. This algorithm focuses on the shape of remote-sensing reflectance, and it can remove the influence of the amplitude of remote-sensing reflectance from the retrieval result. The accuracy of this optimization algorithm is acceptable according to both simulated and in situ data. The percentage of mean square root (RMSP) of the percentage of the phytoplankton absorption coefficient to the total absorption coefficient at 440 nm [ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> (440 nm)] between the retrieved and the simulated is 18.39%. The RMSP of the total absorption coefficient at 440 nm [ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> (440 nm)] between the retrieved and the simulated is 3.65%. The RMSP of the percentage of MA [ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> ] between the retrieved and the simulated is 13.60%. The RMSP of the colored dissolved organic matter (CDOM) absorption coefficient slope [ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> ] between the retrieved and the simulated is 5.89%. The RMSP of the particle backscatter coefficient slope [ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Y</i> ] between the retrieved and the simulated is 30.46%. In Taihu Lake, the RMSPs of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> (440 nm), <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</i> (440 nm), <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> , and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> between the retrieved and the measured are 36.59%, 35.70%, 19.25%, and 16.80%, respectively. The retrieved percentage of MA ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> ) and Scenedesmus obliquus (1 - <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> ) by this model from August 2006, October 2006, to November 2008 indicates the variation trend of algal species in different seasons. This trend accords with the results from previous studies and observations. This paper extends and advances the previous retrieval methods and confirms that the genetic optimization algorithm can be used to retrieve the information of water constituents in the high turbid and eutrophic inland water mass.

Effect of enhanced coagulation by KMnO4 on the fouling of ultrafiltration membranes

Pre-coagulation enhanced by KMnO(4) before ultrafiltration (KCUF) was compared with normal pre-coagulation by alum (CUF) in the ultrafiltration of water from the Songhua River, China. The trans-membrane pressure (TMP) with KCUF was much lower than that when alum alone was used. With KCUF a slower increment of TMP occurred, even under conditions of high river water turbidity. The results also showed that the removal of COD, UV(254) and TOC was appreciably higher after adding 0.5mg/L KMnO(4) compared with CUF. Although assimilable organic carbon (AOC) was increased by permanganate treatment, the AOC of the permeate from KCUF was nearly the same as that from CUF, showing that the cake layer on the surface of KCUF membrane could adsorb small molecules more effectively than that of CUF. This result was confirmed by the apparent molecular weight (MW) distribution measured by size exclusion chromatography (SEC). It was shown that flocs formed by KMnO(4) and alum were larger than those formed only by alum, causing higher removal of flocs and higher permeation flux. Lower NOM was found in the permeate from the KCUF systems because oxidation and adsorption of organic matter on the flocs occurred. The membrane was partly clogged by organic matter or other materials including some small flocs.

Roughing filtration as an effective pre-treatment system for high turbidity water

Effective water treatment is the prime goal of every water treatment facility. Chakwal Water Treatment Plant in Pakistan has been treating high-turbidity surface water through crude coagulation, sedimentation and slow sand filtration since the early 1980s. The process has always been tedious in terms of high coagulant dosage, large volumes of sludge and short filter runs especially after wet spells. A laboratory-scale study was conducted to see if roughing filtration, as the pre-treatment process, would help in reducing coagulant dose and sludge volume and improving effluent quality. Results indicated that up-flow rouging filtration with media grades decreasing in the direction of flow could reduce wet weather raw water turbidity (by more than 90%) and coagulant dose. Overall, the plant could save over US $54,000 annually in terms of coagulant cost only. Longer filter runs, improved product water quality leading to lower chlorine dose requirement, would be additional benefits.

Turbidity characterizes the reproduction areas of pikeperch ( Sander lucioperca (L.)) in the northern Baltic Sea

The pikeperch ( Sander lucioperca (L.)) is an economically important fish species occurring in the fresh and brackish waters of Europe. To evaluate the distribution and extent of the reproduction areas in the northern Baltic Sea, a field survey was carried out in two separate coastal areas. Presence/absence data were used to develop a geographic information system (GIS)-based predictive spatial distribution model, where high resolution raster maps of the focal environmental variables and a logistic regression equation were used to predict the probability of larval occurrence. The results indicated that the pikeperch reproduction areas are located in the innermost archipelago zone where high water turbidity best explained their presence. Turbidity was related to several other variables such as fetch and depth. Contrary to our preliminary hypothesis, surface water temperatures measured during the survey had no significant effect in the model due to the low spatial variation in the measured values. Since turbidity is possible to determine by remote sensing methods, the probability maps can be cost-effectively extended to more extensive coastal areas with proper validation.

Assessing the risk posed by high-turbidity water to water supplies

The objective of this study is to assess the risk of insufficient water supply posed by high-turbidity water. Several phenomena can pose risks to the sufficiency of a water supply; this study concerns risks to water treatment plants from particular properties of rainfall and raw water turbidity. High-turbidity water can impede water treatment plant operations; rainfall properties can influence the degree of soil erosion. Thus, water turbidity relates to rainfall characteristics. Exceedance probabilities are presented for different rainfall intensities and turbidities of water. When the turbidity of raw water is higher than 5,000NTU, it can cause operational problems for a water treatment plant. Calculations show that the turbidity of raw water at the Ban-Sin water treatment plant will be higher than 5,000NTU if the rainfall intensity is larger than 165mm/day. The exceedance probability of high turbidity (turbidity >5,000NTU) in the Ban-Sin water treatment plant is larger than 10%. When any water treatment plant cannot work regularly, its ability to supply water to its customers is at risk.

Investigation on flocculation process of composite poly-Si-Fe coagulant

A new composite polymer, poly-Si-Fe coagulant (PSF), was prepared by copolymerization. The influences of flocculation time, flocculation speed and settling time on the amount of residual particulates in treated water after coagulation using PSF as coagulant in treating various water samples were investigated in comparison with those of polyferric aluminum (PFA). Flocculation coefficient (K A) and destruction coefficient (K B) of PSF and PFA were calculated theoretically. The results show that a close collaboration between flocculation speed and flocculation time of PSF should be performed in order to achieve higher coagulation efficiency. A moderate flocculation speed and flocculation time should be applied in treating hight urbidity water, and a moderate flocculation speed and longer flocculation time should be applied to treat low turbidity water. For surface water, flocculation speed should not be too higher or too lower by using PSF. PFA floc scan be smashed easily than PSF with increasing the floccul...

GIS를 이용한 댐 저수지의 흙탕물 발생 가능성 비교 평가

본 연구에서는 GIS 기반 토사유실모델과 유사전달률 그리고 유효저수용량을 고려하여 댐 저수지별 흙탕물 발생 가능성을 분석하였다. 이를 위해 DEM, 토양도, 토지피복도 등의 공간자료를 기반으로 RUSLE 모델의 입력인자를 평가하여 유역대책 수립시 필요한 각 유역별 취약인자를 분석하였으며, 고랭지밭 특성을 고려한 토사유실량 평가를 통해 강우시 유역내 토사발생 잠재성을 분석하였다. 또한 유역면적을 고려한 유사전달률을 통해 유역별 토사유출량을 계산한 결과 충주댐과 소양강댐이 가장 높은 값을 나타내었으며, 유효저수용량을 고려한 유사농도 분석결과에서는 임하댐과 충주댐이 각각 0.791 <TEX>$kg/m^3/yr$</TEX>와 0.526 <TEX>$kg/m^3/yr$</TEX>로 가장 높게 나타났다. 특히 임하댐의 토사유출량은 소양강댐유역에 비해 약 2.36배 낮게 나타났으나 임하댐 저수지의 유효저수용량이 소양강댐에 비해 약 4.48배 작아 유사농도는 오히려 임하댐 저수지가 1.90배 높게 분석되었다. 본 연구에서는 10년 평균 강우사상을 이용하여 유사농도를 계산하였으며, 이를 통해 각 유역별 토양, 지형, 식생, 경작상태 그리고 유효저수용량 측면을 검토할 수 있었다. 따라서 이러한 정량화된 유사농도 자료들은 저수지의 고탁수 발생 잠재성을 평가할 수 있고 저수지 관리를 위한 효과적인 도구로도 활용될 수 있으리라 판단된다. The muddy water occurrence possibility of reservoir were analyzed by considering GIS based soil erosion model, sediment delivery ratio and effective reservoir capacity. For the purpose, the weakness factors for the establishment of countermeasures of basin were analyzed by evaluating input factors of RUSLE model based on spatial data such as DEM, soil map, landcover map and so on. The potential of soil erosion was estimated considering highland upland. The sediment yields of Chungju-Dam and Soyanggang-Dam showed the highest result in sediment yield using sediment delivery ratio with considering basin area. The sediment concentration of Imha-Dam and Chungju-Dam showed the highest value as 0.791 <TEX>$kg/m^3/yr$</TEX> and 0.526 <TEX>$kg/m^3/yr$</TEX> respectively in sediment concentration with considering effective reservoir capacity. Especially, sediment yield of Imha-Dam was about 2.36 times lower than Soyanggang-Dam, but the sediment concentration was 1.90 times higher preferably, because the effective reservoir capacity of Imha-Dam was about 4.48 times lower. This study calculated sediment concentration using the 10 years mean rainfall event and could consider the aspects of soil, terrain, landcover, cultivation condition and effective reservoir capacity of each basin effectively through the results. Therefore, these quantitative sediment concentration data could be used to estimate the potential of high density turbid water for reservoir and applied with effective tools for the management of reservoir.

A temporal analysis on the dynamics of deep-sea macrofauna: Influence of environmental variability off Catalonia coasts (western Mediterranean)

A seasonal analysis of deep-sea infauna (macrobenthos) based on quantitative sampling was conducted over the Catalan Sea slope, within the Besòs canyon (at ∼550–600 m) and on its adjacent slope (at 800 m). Both sites were sampled in February, April, June–July and October 2007. Environmental variables influencing faunal distribution were also recorded in the sediment and sediment/water interface. Dynamics of macrobenthos at the two stations showed differences in biomass/abundance patterns and trophic structures. Biomass was higher inside the Besòs canyon than on the adjacent slope. The community was mostly dominated by surface-deposit feeding polychaetes (Ampharetidae, Paraonidae, Flabelligeridae) and crustaceans (amphipods such as Carangoliopsis spinulosa and Harpinia spp.) inside the canyon, while subsurface deposit feeders (mainly the sipunculan Onchnesoma steenstrupii) were dominant over the adjacent slope. The taxonomic composition in the suprabenthic assemblages of polychaetes, collected on the adjacent slope by a suprabenthic sledge, was clearly different from that collected by the box-corer. The suprabenthic assemblage was dominated by carnivorous forms (mainly Harmothoe sp. and Nephthys spp.) and linked to higher near-bottom turbidity. Inside Besòs a clear temporal succession of species was related to both food availability and quality and the proliferation of opportunistic species was consistent with higher variability in food sources (TOC, C/N, δ 13C) in comparison to adjacent slope. This was likely caused by a greater influence of terrigenous inputs from river discharges. Inside the canyon, Capitellidae, Spionidae and Flabelligeridae, in general considered as deposit feeders, were more abundant in June–July coinciding with a clear signal of terrigenous carbon (depleted δ 13C, high C/N) in the sediments. By contrast, during October and under conditions of high water turbidity and increases of TOM, carnivorous polychaetes (Glyceridae, Onuphidae) increased. Total macrobenthos biomass found over Catalonian slopes were higher than that found in the neighboring Toulon canyon, probably because the two canyons are influenced by different river inputs, connected with distinct terrigenous sources.

Evaluation of Alternative Media for Pebble Matrix Filtration Using Clay Balls and Recycled Crushed Glass

Protecting slow sand filters (SSFs) from high-turbidity waters by pretreatment using pebble matrix filtration (PMF) has previously been studied in the laboratory at University College London, followed by pilot field trials in Papua New Guinea and Serbia. The first full-scale PMF plant was completed at a water-treatment plant in Sri Lanka in 2008, and during its construction, problems were encountered in sourcing the required size of pebbles and sand as filter media. Because sourcing of uniform-sized pebbles may be problematic in many countries, the performance of alternative media has been investigated for the sustainability of the PMF system. Hand-formed clay balls made at a 100-year-old brick factory in the United Kingdom appear to have satisfied the role of pebbles, and a laboratory filter column was operated by using these clay balls together with recycled crushed glass as an alternative to sand media in the PMF. Results showed that in countries where uniform-sized pebbles are difficult to obtain, cla...

Tidal rhythmites in a mixed-energy, macrotidal estuarine channel, Gomso Bay, west coast of Korea

Well-developed tidal rhythmites are documented from the intertidal point bar of sinuous tidal channel in Gomso Bay, west coast of Korea. Associated with inclined heterolithic stratification, rhythmites constitute the upper part of fining-upward succession formed by the lateral migration of a point bar. Occurring between mean sea-level and mean high water level, rhythmites commonly overlie rhythmic climbing-ripple cross-laminations. Various rhythmicities are registered in laminae thicknesses, which reflect hierarchical tidal cycles ranging from semidiurnal to monthly tidal cycles. Inferred neap–spring tidal cycle (half-synodic) thins upwardly with a proportionately reduced number of preserved laminae in the cycle. Such vertical organization of rhythmites seems to reflect decreased accommodation space through deposition. Tidal rhythmites exhibit longitudinal variation within fluvial–tidal transition with best developed ones formed in a highly meandering tidal channel, where the influence of offshore waves is minimal due to confined channel morphology that is characterized by low energy level in association with high water turbidity. Comparison of spectral peaks between modern and simulated rhythmites further substantiates that tidal rhythmites can serve as a reliable indicator of paleotide, paleoelevation and paleogeography of mixed energy, tide-dominated estuaries.

Methylmercury in tailings ponds of Amazonian gold mines (French Guiana): Field observations and an experimental flocculation method for in situ remediation

Sites of monomethylmercury (MMHg) production in Amazonian regions have been identified in hydraulic reservoirs, lake sediments and wetlands, but tailings ponds have not yet received sufficient attention for this purpose. This work evidenced high MMHg production within the water column and the interstitial water of two tailings ponds of French Guiana Au mines located; (i) in a small scale exploitation (Combat) where Hg was used for Au amalgamation, and (ii) in an industrial on-going Au mine (Yaoni) processing without Hg. The (MMHg)D maximum (2.5 ng L−1) occurred in the oxic water column above the sediment-water interface (SWI) of the most recent tailings pond (Combat), where the substrate was fresh, the redox transition was sharp and the pool of total Hg was large. In the Yaoni pond, the (MMHg)D maximum concentration (1.4 ng L−1) was located at the SWI where suboxic conditions prevailed. Using the (MMHg)D concentration as a proxy for Hg methylation rates, the present results show that Hg methylation may occur in various redox conditions in tailings ponds, and are favored in areas where the organic matter regeneration is more active. A 3-month long laboratory experiment was performed in oxic and anoxic boxes filled with high turbidity waters from the Combat Au mine to simulate tailings ponds. Slaked lime was added in an experimental set (2 mg L−1) and appeared to be very efficient for the reduction of suspended particulate matter (SPM) to environmentally acceptable concentrations. However, at the end of the experiment, large (MMHg)D concentrations were monitored under treated anoxic conditions with the (MMHg)D maximum located at the SWI above the Fe-reducing zones. No (MMHg)D was detected in oxic experiments. The use of slaked lime for SPM decantation appears to be an efficient and non-onerous process for Au miners to avoid Hg methylation in tailings ponds when it is combined with rapid drainage of the mine waters. A subsequent human intervention is however necessary for the recovery of soil structure through the cover of dried ponds with organic rich materials and reforestation to avoid the stagnation of rain waters and the occurrence of anoxia.

Fish assemblages in the Mfolozi–Msunduzi estuarine system, KwaZulu-Natal, South Africa, when not linked to the St Lucia mouth

The fish community of the Mfolozi–Msunduzi estuarine system was investigated with particular emphasis on its role as a nursery area for marine fish when the adjacent St Lucia mouth is closed. The mouth was open during March 2007 and 2008 with high-turbidity river water flowing into the sea, and was closed during August 2007 and 2008. Fish were sampled biannually with seine-nets during March and August in 2007 and 2008 at five sites throughout the system. A total of 5 886 fish from 59 species were recorded, with a higher number of species and CPUE in the Mfolozi Estuary than in the Msunduzi Estuary. Seine-net catches were dominated by Ambassis gymcocephalus, Ambassis natalensis, Leiognathus equula and Valamugil cunnesius. Juveniles of marine spawning species were present throughout the study period, even when the mouth was closed. The sampled fish assemblage structure was influenced by significant temporal differences between the four biannual sampling seasons, with relatively small spatial differences between the sampling areas. Temperature, salinity and sediment characteristics were most responsible for the structure of the fish assemblage as sampled by seine-nets. The results emphasise the importance of the Mfolozi–Msunduzi estuarine system as an alternate nursery area.

Water treatment by sedimentation and slow fabric filtration using Moringa oleifera seeds

The main objective of this work was to evaluate the suitability and efficiency of a natural coagulant from Moringa oleifera seeds in treating high turbidity water in the processes of slow direct filtration and sedimentation. In developing countries such as Brazil, the technologies for water treatment shall enable people living in potable-water deficient regions to purify water in easy and self-sustainable ways and at a low cost as well. Within this proposition, a potential use of M. oleifera has been suggested in several previous studies. In this work, a flocculation device made of pet bottles plus three filters consisting of pet bottles and non-woven synthetic fabric was used in the water treatment by slow direct filtration. The water output to the filters was of approximately 4 m³m-² per day. The water treatment by sedimentation comprised a flocculation unit made of pet bottles and a sedimentation tank. Synthetic bentonite-water was used as the untreated water, which was chosen due to its proper qualitative characteristics for the experiments. The data demonstrated that the M. oleifera coagulant was efficient in the treatment of water with high turbidity (50 to 100 NTU) in the tested systems of slow filtration through synthetic non-woven fabric and of sedimentation. Key words: Moringa oleifera, slow filtration, sedimentation, purification of water.

Suspended Matter, Chl-a, CDOM, Grain Sizes, and Optical Properties in the Arctic Fjord-Type Estuary, Kangerlussuaq, West Greenland During Summer

Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM), and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66°) in August 2007 along with optical properties. These comprised diffuse attenuation coefficient of downwelling PAR (Kd(PAR)), upwelling PAR (Ku(PAR)), particle beam attenuation coefficient (cp), and irradiance reflectance R(−0, PAR). PAR is white light between 400 and 700 nm. The estuary receives melt water from the Greenland Inland Ice and stations covered a transect from the very high turbid melt water outlet to clear marine waters. Results showed a strong spatial variation with high values as for suspended matter concentrations, CDOM, diffuse attenuation coefficient Kd(PAR), particle beam attenuation coefficients (cp), and reflectance R(−0, PAR) at the melt water outlet. Values of optical constituents and properties decreased with distance from the melt water outlet to a more or less constant level in central and outer part of the estuary. There was a strong correlation between inorganic suspended matter (SPMI) and diffuse attenuation coefficient Kd(PAR) (r2 = 0.92) and also for particle beam attenuation coefficient (cp; r2 = 0.93). The obtained SPMI specific attenuation—Kd*(PAR) = 0.13 m2 g−1 SPMI—and the SPMI specific particle beam attenuation—cp* = 0.72 m2 g−1—coefficients were about two times higher than average literature values. Irradiance reflectance R(−0, PAR) was comparatively high (0.09−0.20) and showed a high (r2 = 0.80) correlation with Ku(PAR). Scattering dominated relative to absorption—b(PAR)/a(PAR) = 12.3. Results strongly indicated that the high values in the optical properties were related to the very fine particle sizes (mean = 2–6 μm) of the suspended sediment. Data and results are discussed and compared to similar studies from both temperate and tropical estuaries.