High Turbidity Levels Research Articles

Effects of Inorganic Turbidity on the Phytoplankton of an Amazonian Lake Impacted by Bauxite Tailings

The dumping of bauxite tailings into Batata Lake, an Amazonian clear-water lake, generated high levels of turbidity and caused a serious decrease in phytoplankton densities, which could possibly be the result of a photosynthetic limitation due to light attenuation together with an increase in algal sinking due to the adhesion of clay particles. This study aimed to investigate the sinking process through the addition of different suspended clay concentrations in columns containing Batata lake water. Since no effect of the suspended clays on Batata Lake phytoplankton sinking was observed, it was then evaluated, under laboratory conditions, whether the low conductivity of the Batata Lake water could interfere with the algae-clay aggregation process. Cultures of two algal species known to be capable to aggregate to Batata Lake suspended clays in algal culture medium: Staurodesmus convergens and Phormidium amoenum, were added to both the low conductivity Batata Lake water (14 μS cm−1) and the high conductivity algal culture media (WC – 300 μS cm−1 and Z8 – 560 μS cm−1) together with Batata lake suspended clays. In both algal culture media and Batata lake water the two species had their sinking accelerated due to clay adhesion. It is thus suggested that the decrease in phytoplankton densities recorded in Batata Lake may not be related to an increase in phytoplankton loss rates due to algal-clay aggregation, but rather are a consequence of decreasing growth rates because of light attenuation.

Comparative Taxonomic Richness and Abundance of Late Ordovician Gastropods and Bivalves in Mollusc-rich Strata of the Cincinnati Arch

Using a field analysis of Upper Ordovician mollusc-rich faunas of the Cincinnati Arch, this study tests whether the large-scale patterns of Ordovician gastropods and bivalves observed in a companion study are maintained at the finer scales of individual strata and localities, and when utilizing abundance data in addition to taxonomic richness. Non-metric multidimensional scaling and several statistical analyses show that the taxonomic richness and abundance of these classes within samples were significantly negatively correlated, such that bivalve-rich settings were only sparsely inhabited by gastropods and vice versa. There also were important environmental differences between these classes. Gastropods were most dominant in shallow, carbonate-rich, and generally low-turbidity settings. Gastropods also occurred in restricted lagoons, where bivalves were only minor elements. In contrast, bivalves were most dominant in deep subtidal, siliciclastic shales with high levels of turbidity. Both in terms of abundance and taxonomic richness, these results strongly support those observed at the larger scales of paleocontinents and the globe. Taken together, these results argue that, despite similar taxonomical diversification patterns of these classes at the global scale and heterogeneous patterns among paleocontinents and among regions within Laurentia, gastropods and bivalves had quite different, yet unchanging, environmental distributions throughout the Ordovician, and that these classes did not co-occur to a significant degree, either in terms of taxonomic richness or abundance.

Ultrafiltration-nanofiltration for removal of hydrogen sulfide, elemental sulfur, and sulfate from a municipal groundwater

The City of Delphos, Ohio implemented a study to determine the most effective method of reducing total dissolved solids (TDS), sulfate, and hardness. A desktop and pilot study determined that dissolved oxygen was oxidizing hydrogen sulfide gas in the wellfield and forming element sulfur manifesting itself via high turbidity levels (>20 NTU). While chemical resolubilization via sodium metabisulfite was able to reduce turbidity by +90%, filtration was still required prior to nanofiltration (NF) to mitigate NF plugging. Zenon ultrafiltration effectively reduced feed water turbidity from over 20 NTU to less than 0.15 NTU. The resulting feed water to the NF system eliminated NF fouling from particle plugging. NF was effective for reducing inorganic ions including hardness and TDS.

Coral reefs in a high-latitude, siliciclastic barrier island setting: reef framework and sediment production at Inhaca Island, southern Mozambique

Inhaca Island (southern Mozambique) is located in a high-latitude setting along the seaward margins of the estuarine Maputo Bay and is subject to fluctuations in temperature and salinity, and high sedimentation and turbidity levels. Coral reefs are developed sporadically along the margins of intertidal channels, but framework development is severely restricted. Coral growth is bathymetrically limited (never exceeding 6-m depth), and framework accumulation is only present in the upper 1–2 m. Massive Porites sp. produce a basic reef structure, with other coral genera (mainly Acropora sp., Favia sp., Platygyra sp., Pocillopora sp., and Montipora sp.) colonizing available substrata. Sediment samples also indicate restricted carbonate sediment production, with siliciclastics (mainly quartz) a major sediment contributor (often >90%) and carbonate grain assemblages differing from those normally associated with lower-latitude reefs. Although corals, molluscs and coralline algae (including rhodoliths) represent dominant grain constituents, Halimeda is absent and there is a low diversity (four species identified) of benthic foraminifera (mainly Amphistegina sp.). Grain associations are therefore somewhat transitional in character, comprising elements of both tropical (chlorozoan) and temperate (foramol) grain assemblages. These patterns of reef and associated carbonate production emphasize the marginal character of these reef environments, which form one end member in a broad spectrum of marginal reef systems that are now being identified in a range of both high- and low-latitude settings.

DRINKING WATER MICROBIOLOGY RESULTS, USING A COMBINATION METHOD OF FLOCCULATION AND CHLORINATION, IN CONTROL HOUSEHOLDS VS. INTERVENTION HOUSEHOLDS, SAN JUAN SACATEPEQUEZ, GUATEMALA, 2000.

Exposure to contaminated water through ingestion of drinking water or through recreational activities is a significant mode of transmission of gastrointestinal pathogens that cause death in low income countries. In Guatemala most of the people do not have access to safe drinking water and the development of products to improve quality of drinking water is necessary. To achieve this objective a pilot study testing a new method for the reduction of microbial, organic and heavy metals in water was conducted in rural communities in Guatemala. One hundred randomly selected households were evaluated and randomly assigned in four intervention and one control groups. Three of the intervention groups received flocculant, a new product to be tested that clarifies water through flocculation and disinfects water at the same time; another intervention group received chlorine meanwhile, whereas the control group did not receive an intervention. Baseline household water samples, evaluated for total coliforms, Eschericha coli and turbidity showed no potable water, and high levels of turbidity. The proportion of potable water samples after treatment varied by treatment group, there was a significant improvement in water quality among the four intervention groups, but no a significant difference between the floccutant and the chlorine group. The turbidity decreased significantly in the flocculant users compared to chlorine users. The product showed an improvement in the water potability as well as chlorine bleach, and significantly decreased water turbidity. Based on these findings five hundred households were enrolled and randomly assigned four: flocculant and a water storage vessel, flocculant only, a chlorine solution and chlorine alone. At baseline, one percent of the water samples analyzed was potable, but during fifty two weeks of surveillance up to sixty percent potability was observed in the intervention groups. The turbidity decreased significantly in the water samples treated with the flocculant. This new technology is a functional and inexpensive method to provide safe drinking water in rural communities.

Impacts to water quality and fish habitat associated with maintaining natural channels for flood control.

Field investigation conducted on Boulder Creek in Boulder, Colorado evaluated impacts of flood control maintenance activities on flood conveyance, water quality, and fish habitat. Thirty-nine transects were monitored at one control site and two maintenance sites over a period of eight months. Each site was visited on more than 50 occasions in order to characterize pre- and post-maintenance conditions, and to monitor maintenance activities. Measurements along the transects included substrate composition, flow depth, velocity, and elevation. Reach-average values were assigned to variables such as in-stream vegetation, streambank stability, and woody vegetation before and after maintenance. Water temperature, dissolved oxygen, pH, specific conductance, and turbidity were sampled, and habitat suitability indices were developed pre- and post-maintenance for seven indicator fish species. Water quality impacts during maintenance consisted of high turbidity levels (> 400 NTU), which retumed to background levels (0.1-15 NTU) overnight, as well as changes in mean temperature and pH. Alteration of physical channel characteristics as a result of maintenance had limited effects on habitat quality for four of seven fish species, but caused improvements in habitat quality for three fish species. The main implications of this study for floodplain management are that: (1) Flood control maintenance practices can be in direct conflict with water quality and fish habitat objectives, and should be carefully designed and implemented by an interdisciplinary team. (2) Physical habitat for some fish species can be improved as well as reduced by maintenance activities. Habitat suitability curves may be useful tools for evaluating limiting factors of the habitat and for identifying opportunities for habitat improvements as part of maintenance.

Reef development at Inhaca Island, Mozambique: coral communities and impacts of the 1999/2000 Southern African floods.

Inhaca Island, southern Mozambique, is located towards the southerly latitudinal limits of coral reef growth. Reef development is restricted to the margins of channels which dissect intertidal flats on the Maputo Bay side of the island, and to depths of around 6 m. In contrast to lower latitude reefs, reef development is therefore both spatially and bathymetrically restricted (largely due to high turbidity levels). These natural stress levels were exacerbated, via increased freshwater and sediment discharge, during the severe floods of late 1999/early 2000. Flood impacts varied but were most significant on reefs on the inner (western) side of the island where live coral cover (LCC) decreased from 60.5% (1999) to 24.0% (2001). This is attributed to freshwater-induced bleaching. Dead in situ coral cover increased from 18.6% (1999) to 51.3% (2001). Reefs on the southern tip of the island, by contrast, were relatively unaffected. It is suggested that this largely reflects a closer proximity to the open Indian Ocean which mitigated the effects of freshwater dilution.

ASTER measurement of supraglacial lakes in the Mount Everest region of the Himalaya

AbstractWe demonstrate an application of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images to detect and monitor supraglacial lakes on glaciers in the Mount Everest region in Tibet (Xizang) and Nepal. ASTER offers powerful capabilities to monitor supraglacial lakes in terms of (1) surface area, growth and disappearance (spatial resolution =15m), (2) turbidity (15m resolution), and (3) temperature (90m resolution). Preliminary results show an overall similarity of supraglacial lakes on three glaciers. Lakes have widely varying turbidity as indicated by color in visible/near-infrared bands 1–3, the largest lakes being bright blue (highly turbid), cold (near 0°C) and hydraulically connected with other lakes and supraglacial streams, while small lakes are mostly darkblue (relatively clear water), warmer (>4°C), and appear hydraulically isolated. High levels of turbidity in supraglacial lakes indicate high rates of meltwater input from streams or erosion of ice cliffs, and thus are an indirect measure relating to the activity and hydraulic integration of the lake with respect to other lakes and streams in the glacier.

Stratification and Circulation in a Shallow Turbid Waterbody

Shallow waterbodies are often assumed to be well mixed in the vertical. However, when they are characterised by high turbidity levels, absoption of solar heating within a relatively thin surface layer can produce thermal stratification. Results from an intensive monitoring program have been combined with three-dimensional circulation modelling to examine the diurnal stratification cycles in a small turbid waterbody. The waterbody, known as Rushy Billabong, is located in southeastern Australia and its high turbidity coupled with forcing by wind and solar radiation resulted in regular diurnal cycles of stratification and overturning. Under conditions of light wind and high solar radiation, the model results were generally consistent with the observed temperature field. However, under stronger winds, preferential cooling and sinking of shallow water around the edge of the lake began to contribute significantly to the interior stratification. Model estimates then became more sensitive to the detailed bathymetry and the choice of turbulence parameterisation. The level of stratification is also shown to influence the circulation in the billabong by trapping the wind-driven flow near the surface. Insights provided by the observations and modelling may have broader implications for the management of small turbid systems such as settling ponds, aquaculture ponds, and some natural wetlands.

Sediment yields and turbidity records from small upland subcatchments in the Warragamba Dam Catchment, southern New South Wales

Accelerated rates of soil erosion, following European settlement in Australia, pose a major threat to river ecosystems and water supply storages with agricultural catchments, such as Warragamba Dam (the main water supply dam for Sydney). Sediment yields from 1988 to 1999 have been determined by stream monitoring for 6 small grazing catchments located near Goulburn in southern New South Wales, in the outer Warragamba catchment. Average specific sediment yields were 0.07 t/ha.year from 3 small catchments of around 10 ha, where the drainage lines were not continuously gullied, and the drainage lines were undisturbed. Sediment yields from larger gullied catchments of 29, 52, and 510 ha were at least an order of magnitude higher than from the ungullied catchments at around 1 t/ha.year. Gullies continue to be the dominant source of sediment from these subcatchments despite indications that yields from gullies in the Southern Tablelands are much less than in the first few decades following settlement and are gradually declining as gullies move towards a stable vegetated state. Measured sediment yields from this study are comparable with yields for southern New South Wales determined using other methods, such as radionuclide and farm dam survey techniques. The impact of soil conservation works, such as sediment trapping and grade stabilisation works, on sediment yields can be mixed depending on the activity of the gully being treated and the mobility of the bed sediments. Turbidity levels from runoff events from the gullied catchments were an order of magnitude higher than from the ungullied catchments. For the Warragamba catchment turbidity levels are scale dependent; at the farm paddock scale turbidities are generally low where the land use is grazing, they increase dramatically at the subcatchment scale where active gullies dominate the drainage network, and then drop back again at the large river catchment scale. Turbidity is positively correlated with sediment concentration, so works that reduce sediment loads will also reduce the turbidity of water leaving the subcatchment. However, the link between high turbidity levels in small upland catchments and downstream water quality in large complex river basins is tenuous.

Quantification of surface suspended sediments along a river dominated coast with NOAA AVHRR and SeaWiFS measurements: Louisiana, USA

The ability to quantify suspended sediment concentrations accurately over both time and space using satellite data has been a goal of many environmental researchers over the past few decades. This study utilizes data acquired by the NOAA Advanced Very High Resolution Radiometer (AVHRR) and the Orbview-2 Sea-viewing wide field-of-view (SeaWiFS) ocean colour sensor, coupled with field measurements to develop statistical models for the estimation of nearsurface suspended sediments and suspended solids. 'Ground truth' water samples were obtained via helicopter, small boat and automatic water sampler within a few hours of satellite overpasses. The NOAA AVHRR atmospheric correction was modified for the high levels of turbidity along the Louisiana coast. Models were developed based on the field measurements and reflectance/radiance measurements in the visible and near infrared Channels of NOAA-14 and Orbview-2 SeaWiFS. The best models for predicting surface suspended sediment concentrations were obtained with a NOAA AVHRR Channel 1 (580-680 nm) cubic model, Channel 2 (725-1100 nm) linear model and SeaWiFS Channel 6 (660-680 nm) power model. The suspended sediment models developed using SeaWiFS Channel 5 (545-565 nm) were inferior, a result that we attribute mainly to the atmospheric correction technique, the shallow depth of the water samples and absorption effects from non-sediment water constituents.

Microfiltration pilot plant performance investigations into lake water treatment

A 6-month study was carried out at AMGA's research centre, using a microfiltration pilot plant to treat lake water from the Brugneto dam. Specific tests were carried out to challenge the membrane with respect to its ability to remove high levels of turbidity, E. coli , micro-algae, aluminium and Cryptosporidium oocysts. The microfiltration membrane used in this study was clearly fully able to reject protozoan oocysts at a level not easily obtainable using conventional treatment technologies, as well as faecal indicator bacteria.

Membrane filtration of high turbidity sources

Membrane filtration processes have become widely used for low turbidity water sources that require particle removal and disinfection. In cases where the feed water contains high turbidity levels or high fouling tendencies, pre-treatment has been required to allow the membranes to operate efficiently. Submersion membranes have allowed direct treatment on many of these water supplies but operate under vacuum. This presents limitations on operating flux and design conditions for incorporating into existing facilities. The treatment unit designs are also very expensive to implement for small water treatment applications. A recently developed pressure driven ultrafiltration (UF) membrane is being tested on several different water sources and has demonstrated exceptional operation on high turbidity feed water sources. The module design includes a single potted end with the membrane fibers looped on the bottom to allow draining of solids from the module. The UF membrane filters outside to inside and has been operated on feed water turbidity levels up to 200 ntu. The availability of a pressure driven hollow fiber membrane that can efficiently filter high suspended solids water sources can provide a cost effective solution for many small to medium sized water supplies. Conditioning the feed water with a coagulant or direct filtration of high turbidity feed water can be used depending on the organic material present without settling or other clarification process. This eliminates the need for additional structural pretreatment and reduces overall system cost and size. Current limitations include the module size that makes this cost prohibitive for very large systems. Larger membrane systems where high-suspended solids are present in the feed water have been utilizing immersion membrane technologies more and more over the past few years. These systems typically operate under a vacuum and can be used for large water treatment plants as their design allows large filtration modules such as Memcor's CMFS filter block at 880 m3/hr. This allows significant capital cost reductions and allows membrane filtration to be competitive to conventional filtration technologies for virtually all filtration applications. This paper will review the economics and performance of both pressure driven and immersion membrane systems for small to large water supply systems on feed water containing high-suspended solid levels. Actual testing data for the new pressure driven hollow fiber UF membrane and immersion membrane systems will be provided on different water supplies including unconditioned surface water, filter backwash water and coagulated surface water.

Sediment removal by the Lake Apopka marsh flow-way

We review the evidence showing that the high turbidity levels of Lake Apopka are due primarily to resuspended sediments rather than phytoplankton, and that this situation is likely to persist unless there is a fundamental change in the lake. We discuss the reasons why reductions in phosphorus inputs, the gizzard shad removal program, and macrophyte plantings would not bring about such a change. Potentially the marsh flow-way could remove the flocculent sediments because of a unique combination of a very large surface area (125 km2), a mean depth of only 1.7 m, a layer of easily resuspended fluid mud, and a marsh flow-way that is designed to filter the lake volume about 2 times a year. Using several different estimates of the rate of sediment formation in the lake, our model calculates that it would take from 275 to 502 years to remove the sediments, so the lake could not attain clear water in a reasonable length of time. The model is mathematically correct but will give nonsense results if one tries to calculate removal times when the lake is accumulating sediments rather than losing them.

Distribution and dynamics of Posidonia oceanica beds along the Albères coastline

The location and dynamics of Posidonia oceanica beds were studied in the marine natural reserve of Cerbère–Banyuls-sur-Mer (eastern Pyrenees, France), through the mapping of bottom assemblages (transects and image processing) and the monitoring of fixed markers installed at the Posidonia oceanica lower limit. The surface area occupied by continuous beds is relatively limited and localized, whereas the presence of important areas of dead ‘matte’ would seem to indicate that bottom cover by Posidonia oceanica was more extensive in the past. Although the limited extension of the seagrass beds seems to be linked to both a high level of turbidity and severe hydrodynamic conditions, it is hypothesized that the regressions observed are due to lack of sediment.

Charophyte Occurrence, Seed Banks and Establishment in Farm Dams in New South Wales

Farm dams are an important and common water resource in rural Australia. They provide relatively permanent surface water for stock and wildlife. They typically have high turbidity and high levels of disturbance by stock. The occurrence of charophytes in these water bodies was examined, as well as the conditions under which they germinated and established. Charophytes were found in 15% of 65 farm dams surveyed in two regions in New South Wales, Australia. However, charophytes germinated from 64.5% of farm dam seed banks sampled (n = 17). Species found were Chara australis R.Br., C. fibrosa Agardh ex Bruzelius, C. globularis Thuillier, C. muelleri A.Br., Nitella cristata A.Br. and N. tasmanica A.Br. Farm dams in which charophytes were found both in the survey and in the seed bank had lower turbidity, lower dissolved phosphorus levels and more extensive submerged plant communities than average. Charophytes established from the seed banks under experimentally induced water regimes when high water clarity was maintained and the disturbance of stock grazing was removed. Farm dams can support populations of perennial and annual charophyte species, and provide a habitat that is less available in naturally occurring shallow water bodies of the regions.

Effects of turbidity on the feeding ability of the juvenile migrant stage of six New Zealand freshwater fish species

Laboratory tank experiments were used to determine the effect of turbidity levels ranging from 0–640 Nephelometric Turbidity Units (NTU) on mean feeding rates for each species. Mean feeding rates for banded kokopu (Galaxias fasciatus), smelt (Retropinna retropinna), inanga (G. maculatus), and common bullies (Gobiomorphus cotidianus) were all reduced by increased turbidity, but significantly so only for banded kokopu and inanga. Banded kokopu was the most sensitive species as feeding rates at 20 NTU were significantly lower than in clear water, compared with levels over 160 NTU for the other species. Feeding rates for redfinned bullies (Gobiomorphus huttoni) increased with turbidity up to 40 NTU then decreased. Reductions in feeding rate at elevated turbidity levels were the result of a reduced inability to feed, rather than to stress, as exposure to the highest turbidity level did not reduce feeding motivation or appetite. Feeding tests in the dark indicated that, whereas vision was important for feeding by all species, banded kokopu and common bullies had a comparatively well‐developed ability to feed using non‐visual senses. Non‐visual feeding may have reduced the impact of high turbidity levels on feeding for these two species, and could confound attempts to determine the effects of turbidity on visual feeding on live prey.

Effects of high natural seston concentrations on the feeding, selection, and absorption of the oyster Crassostrea gigas (Thunberg)

Feeding, selection and absorption were determined for the Pacific oyster Crassostrea gigas cultivated in the Bay of Marennes-Oléron, over a spring/neap tidal cycle. Physiological determinations were related to the highly variable food environment with continuous recordings of turbidity and fluorescence. In this bay, resuspension processes have a major influence on food availability and quality. Seston characteristics experienced by oysters can be summarized by high turbidity levels from 20 to 350 mg·l −1 and a predominance of the detritic fraction among the organic fraction (mean C/N ratio=16.57). Food is diluted by the fine resuspended sediment, and organic content of particulate matter in the water column decreases from 30% to 10% with increasing seston loads. Significant differences (Ancova, P<0.01), due to low retention efficiencies of the smaller particle size range, were recorded between the food quality (estimated by the organic content and the total pigment content) measured in the water column and the fraction retained by the oyster's gill. Below seston concentrations of 90 mg·l −1 ingestion rate was regulated by pseudofaecal production. Above 90 mg·l −1, a sharp reduction of filtration and rejection rates suggests physical constraints limiting food acquisition. The oyster selectively rejects inorganic from organic particles, enriching the ingested fraction. Amongst the potentially nutritive particles, significantly fewer particles containing phytopigments were rejected relative to organic particles (non-linear regressions, P<0.001). The negative influence, through food dilution, of high seston loads on net absorption efficiency was determined. This efficiency decreases with decreasing organic ingested fraction. Scope for growth calculations confirm the negative influence of seston loads, but show, supported by field growth measurements, that resuspended organic particles play an important role in the oyster's nutrition.

Bactericidal Actions of Hen Egg White Lysozyme and Mutanolysin Against Lactic Acid Bacteria.

Hen egg white lysozyme was more effective than mutanolysin in killing lactic acid bacteria. The lysozyme-reated cell suspension had relatively high levels of turbidity but a low viability. On the other hand, the mutanolysin-reated cell suspension showed rather low levels of turbidity but a high cell survival number. Observations using a scanning electron microscope also showed differences in the appearances of the cells damaged by the treatment with each enzyme. The modes of action of the lysozyme and mutanolysin against the cell wall of lactic acid bacteria appeared to be quite different from each other though these enzymes are both a kind of peptidoglycan N-acetylmuramoylhydrolase. From these facts, it was found that for the killing of lactic acid bacteria, lysozyme is more effective than mutanolysin and the simultaneous use of both enzymes is much more effective than the use of a single type of enzyme.

A land-use and water-quality history of White Rock Lake reservoir, Dallas, Texas, based on paleolimnological analyses

White Rock Lake reservoir in Dallas, Texas contains a 150-cm sediment record of silty clay that documents land-use changes since its construction in 1912. Pollen analysis corroborates historical evidence that between 1912 and 1950 the watershed was primarily agricultural. Land disturbance by plowing coupled with strong and variable spring precipitation caused large amounts of sediment to enter the lake during this period. Diatoms were not preserved at this time probably because of low productivity compared to diatom dissolution by warm, alkaline water prior to burial in the sediments. After 1956, the watershed became progressively urbanized. Erosion decreased, land stabilized, and pollen of riparian trees increased as the lake water became somewhat less turbid. By 1986 the sediment record indicates that diatom productivity had increased beyond rates of diatom destruction. Neither increased nutrients nor reduced pesticides can account for increased diatom productivity, but grain size studies imply that before 1986 diatoms were light limited by high levels of turbidity. This study documents how reservoirs may relate to land-use practices and how watershed management could extend reservoir life and improve water quality.