Showing papers on "Turbidity published in 1987"

Turbidity as a control on phytoplankton biomass and productivity in estuaries

Abstract: In many coastal plain estuaries light attenuation by suspended sediments confines the photic zone to a small fraction of the water column, such that light limitation is a major control on phytoplankon production and turnover rate. For a variety of estuarine systems (e.g. San Francisco Bay, Puget Sound, Delaware Bay, Hudson River plume), photic-zone productivity can be estimated as a function of phytoplankton biomass times mean irradiance of the photic zone. Net water column productivity also varies with light availability, and in San Francisco Bay net productivity is zero (estimated respiratory loss of phytoplankton balances photosynthesis) when the ratio of photic depth ( Z p ) to mixed depth ( Z m ) is less than about 0.2. Thus whenever Z p : Z m Much of the spatial and temporal variability of phytoplankton biomass or productivity in estuaries is explained by variations in the ratio of photic depth to mixed depth. For example, phytoplankton blooms often coincide with stratification events that reduce the depth of the surface mixed layer (increase Z p : Z m ). Shallow estuarine embayments (high Z p : Z m ) are often characterized by high phytoplankton biomass relative to adjacent channels (low Z p : Z m ). Many estuaries have longitudinal gradients in productivity that mirror the distribution of suspended sediments: productivity is low near the riverine source of sediments (low Z p : Z m ) and increases toward the estuary mouth where turbidity decreases. Some of these generalizations are qualitative in nature, and detailed understanding of the interaction between turbidity and estuarine phytoplankton dynamics requires improved understanding of vertical mixing rates and phytoplankton respiration.

Effects of Turbidity in Fresh Waters of Alaska

Abstract: Turbidity results from the scattering of light in water by organic and inorganic particles; however, high turbidities usually are caused by suspended inorganic particles, particularly sediment. For several Alaskan lakes, we found that the depth to which 1% of subsurface light penetrated had a strong inverse correlation with sediment-induced turbidity. We also developed a model that describes the decrease in primary production in shallow interior Alaskan streams caused by sediment-induced turbidity. Euphotic volume in lakes correlated strongly with production of juvenile sockeye salmon (Oncorhynchus nerka). We also observed reduced abundance of zooplankton, macroinvertebrates, and Arctic grayling (Thymallus arcticus) in naturally and artificially turbid aquatic systems. Turbidity measurements correlated less consistently with measures of suspended sediment concentration (total nonfilterable residue), but provided an adequate estimator for use as a water quality standard to protect aquatic habitats.

Turbidity as a Water Quality Standard for Salmonid Habitats in Alaska

Abstract: Evidence both of trophic level changes induced by reduction in light penetration and of more direct effects of sediment and turbidity on aquatic life indicates that turbidity constitutes a valid and useful water quality standard that can be used to protect aquatic habitats from sediment pollution. A review of studies conducted in Alaska and elsewhere indicated that water quality standards allowing increases of 25 or 5 nephelometric turbidity units above ambient turbidity in clear coldwater habitats provide moderate and relatively high protection, respectively, for salmonid fish resources in Alaska. Even stricter limits may be warranted to protect extremely clear waters, but such stringent limits apparently are not necessary to protect naturally turbid systems.

Suspended sediment fluctuations in the Tagus estuary on semi-diurnal and fortnightly time scales

Abstract: Nine multi-ship synoptic surveys of the distribution of suspended sediment, each survey including the distribution at both low and high tide, were carried out over a 12-month period in the mesotidal Tagus estuary in Portugal. Additional measurements of the semi-diurnal fluctuations of suspended sediment concentration and current strength were made at fixed stations during a neap and a spring tide. During the study period, the river discharge of water and suspended sediment remained below the mean annual discharge and did not show a pronounced seasonal fluctuation. A turbidity maximum, defined as an area with suspended sediment concentrations greater than 50 mg l −1 , was absent during neap tides (1·3-m amplitude), but appeared and grew in both extent and turbidity as the tidal amplitude increased. The turbidity maximum was fully developed during spring tides (> 3-m amplitude) with concentrations greater than 50 mg l −1 throughout the entire estuary. Maximum concentrations, reaching as much as 1000 mg l −1 during spring tides, were always found in the inner shallow bay region of the estuary. In contrast to the salinity distribution, which fluctuated between partly stratified during neap tides and well mixed during spring tides, the vertical distribution of suspended matter in the turbidity maximum zone was always stratified with the highest concentrations near the bottom. The semi-diurnal fluctuation of the suspended sediment concentration was negligible during neap tides, but attained magnitudes during spring tides that were comparable to the fortnightly fluctuation. The fluctuation in suspended matter concentration is interpreted as a fortnightly erosion-sedimentation cycle, caused by a cyclic variation in the strength of the bottom currents. Superimposed on this fortnightly cycle is a semi-diurnal cycle. The amount of material involved in these cycles is equivalent to one year's input of suspended sediment by the Tagus river during normal discharge conditions.

Determination of the Angstrom turbidity parameters.

Abstract: We have analyzed the dependence of the Angstrom turbidity parameters on wavelength throughout the visible range by three different methods. We have obtained significant results about the ability of these parameters to represent the turbidity of the atmosphere. An important variation of these coefficients with the wavelength is shown, depending on the method used and the spectral resolution of the data. The log–log plot of aerosol optical thickness vs wavelength appears as an adequate method of obtaining the Angstrom parameters to represent the turbidity of the atmosphere and to model the effect of aerosols on solar radiation.

Field experiment on the influences of suspended clay and P on the plankton of a small lake

Abstract: Independent and interactive effects of phosphorus and clay loading on pelagic community organization and productivity were tested in a small piedmont lake in North Carolina. Twelve limnocorrals (2-m diam, 3 m deep) were used for field manipulations. Treatments (in triplicate) were unaltered controls, P loading of 3.3 mg m−2 d−1, kaolinite clay loading of 100 g m−2 d−1, and combined clay and P loading. Fertilization with P significantly increased rates of turbidity reduction in comparison to controls (Secchi depth increasing at 7.2 vs. 5.8 cm d−1) and also significantly lowered sustained turbidity in treatments under clay loading. Clay loading reduced net community productivity (NCP), Chl a concentrations, and algal cell numbers. Suspended clay also caused a shift in algal community composition; Trachelomonas superba and other flagellates replaced the otherwise dominant blue-green Spirulina major. Fertilization with P increased NCP and algal densities and favored development of the N2-fixing blue-green algae Anabaena spiroides and Anabaena circinalis. Combined P and clay loading produced intermediate values of turbidity, NCP, and Chl a. Simultaneous clay loading eliminated the influence of P fertilization on algal community structure, yielding an assemblage dominated by flagellates. Clay turbidity also caused a shallowing in the daytime distribution of zooplankton.

The role of wind in generating turbidity maxima in the Tay Estuary

Abstract: Variations of wind direction and strength in the Tay Estuary control wave generation and the resultant patterns of suspended sediment concentration in the waters over the extensive tidal flats. Bodies of water with high water concentration peaks advect to occupy sites at which turbidity maxima are normally present at low water. Other low water peaks are generated by ebb tidal current resuspension.

Freshwater phytoplankton in the low salinity region of the River Tamar estuary

Abstract: An investigation was made into the fate of freshwater algae in the Tamar estuary, south-west England, to examine the hypothesis that oxygen minima, observed at the freshwater-brackish water interface, were a consequence of mass mortality of freshwater algae and the subsequent oxidative degradation of the lysed cells by bacteria. The quantity and species composition of algae in the river and estuary were determined by measurements of chlorophyll and cell numbers. Phytoplankton numbers were transformed into biomass by measuring the volume of the cells and calculating the carbon content. Salinity, dissolved oxygen, turbidity, pH and temperature were also recorded. The size of the upper estuarine community was inversely related to freshwater input. During the summer months, very large populations of freshwater algae (up to 8 mg carbon l−1) were observed between 0 and 8‰ salinity, after long periods of low freshwater input. This population was completely dominated by the diatom Cyclotella atomus and was very stable with respect to changing tides, remaining in the estuary until river flow increased. Death of these algae only occurred at salinities greater than 8‰ and oxygen minima were not observed. The oxygen minima were more closely associated with the turbidity maxima than with algal mortality. There is some evidence that the oxygen depletion may be due to decreased photosynthesis as a result of the reduced light availability at the turbidity maxima.

Organics, polymers, and performance in direct filtration

Abstract: The effects of raw water quality, chemical variables, and physical filter variables on direct filtration performance are examined. Cationic polyelectrolytes as sole coagulants are effective in treating low turbidity, colored waters by direct filtration. The polymer dosage is related to the raw water concentration of dissolved organic carbon. Cationic polymers can remove approximately 40% of the TOC and THM precursors. Filtration rate, direct filtration mode (in-line versus flocculation), and water temperature did not have a significant effect on removals. Greater removals were achieved by alum. Direct filtration with cationic polymers is a feasible method of treatment for waters containing 5 mg/L TOC or less. For waters containing relatively high concentrations of humic matter (color) or submicron size particles, direct filtration with a flocculation period produces less head loss development and longer filter runs. UV absorbance is an excellent surrogate parameter for monitoring the removals of TOC and THM precursors.

Calcium carbonate precipitation and turbidity measurements in Otisco Lake, New York

Abstract: Calcium carbonate precipitate, known as “whiting,” forms in a large number of hard water lakes and reservoirs, and thus contributes to turbidity measurements in these systems. Here we document the occurrence of “whitings,” and the associated impact on turbidity, in Otisco Lake, New York. A simple, potentially broadly applicable, technique, measurement of turbidity before and after acidification, successfully quantified this component of turbidity in the lake. Calcium carbonate represented 32 percent of the turbidity in the upper waters of Otisco Lake for a three-month period, and at times was as much as 70 percent. Routine monitoring of this component of turbidity in raw water sources, where it is significant, should provide insight into water quality management and treatment plant operations.

Operational Variables and the Release of Colonized Granular Activated Carbon Particles in Drinking Water

Abstract: Laboratory and field studies were conducted to determine the impact of granular activated carbon (GAC) drinking water filters and various operational variables on the release of populated filtration medium into finished water. Initially, various filtration media were compared. In laboratory column experiments, the surfaces of GAC, sand, and anthracite particles were populated to the same level with heterotrophic plate count (HPC) bacteria. However, GAC supported greater numbers of the coliform Klebsiella oxytoca than the other two media. A comparison of the media from operating drinking water filters showed that GAC-filtered water contained particles with attached HPC and coliform bacteria to a greater extent than sandand anthracite-treated water. The involvement of various operational variables in the increased release of populated fines was evaluated at two facilities. Statistical analyses showed that GAC age does not affect the occurrence of populated fines in filtered water. However, a deeper GAC bed, an increase in applied water turbidity, and an elevated filtration rate were implicated as contributing to the presence of populated filtration medium in drinking water.

Water treatment system

Abstract: A method and apparatus for the removal or reduction of inorganic contaminants, hardness, radionuclides, organic contaminants, odor, turbidity, discoloration, and objectionable taste from water, subjects the water to lime-phosphate softening, aeration, sedimentation, filtration and ion exchange in an automatic cycle especially suited for home and small commercial usage The raw water, such as well water, is first subjected to a cold lime softening and aeration treatment, then to a phosphate treatment followed by settling and filtering The thus treated water is supplied to a pressurized tank feeding a conventional ion exchange water softening unit as the water is tapped for use No heat input is needed but the treated water can be heated as desired for use An electrical control system regulates the water and chemicals input agitation, aeration, the time of chemical treatment in successive stages and the maintenance of a desired head pressure for the treated water The apparatus is compact, fully automatic in operation, low in cost and is well suited for use in private homes

Detecting apparatus of turbidity of oil

Abstract: PURPOSE:To enable the detection of turbidity of a lubricating oil, by introducing the lubricating oil between a light-emitting element and a photosensing element and by varying a distance between these elements. CONSTITUTION:A light from a light-emitting element 1 reaches a photosensing surface 2 through an inner-oil optical path varying to be of distances Da and Db. On the occasion, the intensities Ia and Ib of the light reaching the photosensing surface 2 are expressed by Ia=Io.C.B.e K D ... (I) and Ib= Io.C.B.e K D ... (II) respectively (where Io is an emission intensity of a light- emitting element (in the case when an oil is new with turbidity alpha=0, when no film due to contamination or the like sticks on glass surfaces 3' and 4' and before the emission intensity characteristic of the light-emitting element 1 varies), C is a light absorption coefficient of the film due to the contamination on the glass surfaces, B is a variation coefficient of the emission intensity of the light-emitting element itself, and alpha is the turbidity of the oil (concentration of carbon in the oil). When the percentage of the turbidity of the oil is determined from the equations (I) and (II), therefore, C and B are eliminated and the turbidity alpha can be determined by an equation III.

The Importance of Whiting as a Component of Raw Water Turbidity

Abstract: Water utilities routinely measure turbidity as an indicator of raw water quality and of the need for treatment. Carbonate precipitate (whiting) represents a significant, and at times dominant, component of turbidity in many hard-water lakes and reservoirs. The chemistry, driving forces for occurrence, ubiquity, and important features of whiting are presented in this article. It is recommended that utilities that use hard-water lakes or reservoirs as sources of supply keep apprised of this component of turbidity.

Role of smaller metazoa in water purification and sludge reduction

Abstract: Smaller metazoa appearing in biological treatment process are divided into two types. One is filter feeder such as Rotatoria and another is detritus feeder such as Oilgochaeta. To make clear the role of smaller metazoa in water purification, Philodina erythrophthalma and Aelosoma hemprichi were used as Rotatoria and Oligochaeta individually in this experiment. Smaller metazoa were cultivated under static and dark conditions in LE (Lettuce and egg yolk extract) medium containing several bacteria. The run of experiment consisted of only bacteria (B), bacteria+A. hemprichi (BA), bacteria+P. erythrophthalma (BP), and bacteria+A. hemprichi+P. erythrophthalma (BPA) . Purification efficiency was estimated by TOC, viable count and suspended solid in cultivation medium. The results obtained from this experiment were as follows.(1) In the B system, the turbidity is high and the efficiency of organic matter removal is low because of existence of the large amount of dispersed bacteria.(2) In the BA system, the amount of biomass decreases because the detritus feeder such as A. hemprichi feeds on the detritus, but the turbidity is still high and the efficiency of organic mater removal is not so high because of the presence of dispersed bacteria.(3) In the BP system, the biomass and turbidity decrease and the efficiency of organic matter removal increases, since the filter feeder such as P. erythrophthalma feeds on the dispersed bacteria.(4) And in the BPA system, the amount of biomass decreases most remarkably along with the turbidity reduction and improved efficiency of organic matter removal, because the coexistence of A. hemprichi and P. erythrophthalma whose feeding mechanisms and food habits differ from each other, promotes their predatory activities on the dispersed and flocculated bacteria.It can be concluded that the detritus and filter feeder smaller metazoa in bio-film are contributing greatly to water purification and reducion of biomass.

Optical Heterogeneity in Green Bay

Abstract: Differences in light penetration and light attenuating components and processes are documented along 112 km of the major (NE/SW) axis of Green Bay (Lake Michigan) during a three-day cruise (May 25–27, 1982). Measurements included diffuse attenuation of downwelling irradiance (kd), Secchi disk transparency (SD), phytoplankton pigments (chlorophyll a and phaeophytin), turbidity (Tn), and dissolved color (absorbance). The relative importance of absorption and scattering to attenuation was calculated from paired measurements of kd and SD. Absorption and scattering coefficients were calculated; value estimates were supported by a strong linear relationship between the scattering coefficient (b) and Tn (b = 0.99 *Tn; r2= 097, n = 12). Light attenuation characteristics, including the extent of light penetration and the magnitudes and relative importance of absorption, scattering and individual attenuating components, were found to be heterogenous in space. This heterogeneity is due to the characteristics and positions of entry of fluvial discharges to the bay as they influence levels of dissolved color (Gelbstoff), phytoplankton standing crop, and inorganic particulates. Identification of key processes regulating light penetration and their potential for response to pollution control measures can aid in the development of a water quality management plan for Green Bay.

Succession in zooplankton and hydrophytes of a seasonal water on the west coast of South Africa

Abstract: Certain aspects of the biotic components of a seasonal water, subject to large seasonal fluctuations in physical and chemical features, were investigated. Phytoplankton development and succession were largely dependent on water-depth and turbidity. Observed increases in marginal hydrophyte stands and suspended solid loads of the water were related to eutrophication. The succession of primary consumers was related to food resources and habitat requirements. Factors which influenced the functioning of the aquatic ecosystem were identified as water-depth, turbidity, orthophosphates, chlorides, conductivity and total dissolved solids.

Method for preventing contamination of membrane module

Abstract: PURPOSE:To simultaneously monitor the turbidity of feed water and the contamination level in the membrane module by measuring the turbidity of the concd. water at the outlet from the membrane module. CONSTITUTION:The suspended matter in the raw water from a pipe 1 is removed by the pretreating device 2, then the water is pressurized by a high- pressure pump 4 and introduced into the membrane module 5, the permeated water is discharged from a pipe 6, and the concd. water is taken out from a pipe 7. The SDI of the concd. water flowing in the pipe 7 is measured by a turbidimeter 8, and the concd. water is discarded to the outside of the system by opening a control valve 9 when a turbidity at more than a specified value is detected. Besides, a control valve 10 provided to the pipe 7 is opened to increase the flow velocity of the feed water passing through the membrane surface, and the membrane module 5 can be flushed.