Showing papers on "Turbidity published in 2005"

Remotely-sensed chl a at the Chesapeake Bay mouth is correlated with annual freshwater flow to Chesapeake Bay

Abstract: [1] High freshwater flow delivers excess nutrients to Chesapeake Bay, leading to increased phytoplankton biomass, turbidity, and eutrophication. Low flow in 2002 was associated with a persistent drought that terminated abruptly in autumn 2002, followed by extremely high flow in 2003. This large difference in flow caused improved water quality in 2002 as nutrient loading subsided, and degraded water quality in 2003 with increased loading associated with high flow. We analyzed remotely sensed chlorophyll (chl a) data using an online data analysis tool to quantify the effect of sequential low and high freshwater flow on phytoplankton biomass near the mouth of the Bay. Chl a in the study area was significantly higher in 2003 than in 2002, consistent with strong forcing by freshwater flow and nutrient loading in the nutrient-limited region of the Bay.

Polyacrylamide Use for Erosion and Turbidity Control on Construction Sites

Abstract: Streams and lakes adjacent to construction sites are often heavily impaired by sediment and turbidity coming from areas of exposed soil. A study was conducted to determine if the application of polyacrylamide (PAM) can reduce erosion and runoff turbidity on moderate to steep slopes at construction sites. The test sites were three North Carolina Department of Transportation construction sites in the Piedmont and Coastal Plain. Two PAM products were applied at recommended rates (10.5 and 1.5 kg ha−1; 9.3 and 1.3 lb ac−1) and one half the recommended rates (5.2 and 0.76 kg ha−1; 4.6 and 0.68 lb ac−1) with and without grass seeding and straw mulching. Runoff volumes, turbidity levels, and eroded sediment data were collected after natural rain events. On a 50 percent fill slope, turbidity and sediment loss were significantly decreased with application of seed/mulch but not PAM alone. PAM applied on the seed/mulch treatment did not have statistical effects compared to the seed/mulch alone. Erosion rates of up to 43 t ha−1 were recorded for one storm on bare soil; seed/mulch reduced this by 83 percent. On a 20 percent cut slope, PAM significantly (P

Effects of Sodium Chloride on the Performance of a Sequencing Batch Reactor

Abstract: In this study, we investigated the effects of sodium chloride (concentrations ranging from 0 to 60 g∕L ) on the performance of sequencing batch reactors (SBRs) using a microbial culture developed from a domestic sewage treatment plant. The lab-scale SBRs were fed with synthetic wastewater (acetate as the organic substrate) containing either sodium chloride solution or seawater to ensure consistency in feed composition. It was found that sodium chloride concentrations of up to 10 g∕L stimulated substrate removal. The organic removal efficiency decreased from 96%, when no sodium chloride was added, to 86% when 60 g∕L of sodium chloride was introduced into the influent wastewater. Effluent turbidity increased significantly when the sodium chloride concentration in the wastewater was equal to or above 30 g∕L even though the sludge volume index (SVI) decreased. The increase in effluent turbidity could be caused by the release of nondissolved cellular components due to plasmolysis of microorganisms as observed ...

Fluxes and sources of suspended organic matter in an estuarine turbidity maximum region during low discharge conditions

Abstract: Water column concentrations of total suspended solids (TSS), particulate organic carbon (POC) and particulate nitrogen (PN) were measured at three different depths in four different locations bracketing the estuarine turbidity maximum (ETM) along the main channel of a temperate riverine estuary (Winyah Bay, South Carolina, USA). Measurements were carried out over full tidal cycle (over 24 h). Salinity, temperature, current magnitude and direction were also monitored at the same time throughout the water column. Tidally averaged net fluxes of salt, TSS, POC and PN were calculated by combining the current measurements with the concentration data. Under the extreme low river discharge conditions that characterized the study period, net landward fluxes of salt were measured in the lower part of the study area, suggesting that the landward transport through the main channel of the estuary was probably balanced by export out through the sides. In contrast, the net fluxes of salt in the upper reaches of the study area were near zero, indicating a closed salt balance in this part of the estuary. In contrast to salt, the net fluxes of TSS, POC and PN in the deeper parts of the water column were consistently landward at all four sites in Winyah Bay indicating the non-conservative behavior of particulate components and their active transport up the estuary in the region around the ETM. The carbon contents (%POC), carbon:nitrogen ratios (org[C:N]a) and stable carbon isotopic compositions (d 13 CPOC) of the suspended particles varied significantly with depth, location and tidal stage. Tidally averaged compositions showed a significant increase up the estuary in the %POC and org[C:N]a values of suspended particles consistent with the preferential landward transport of carbon-rich particles with higher vascular plant debris content. The combination of tidal resuspension and flooddominated flow appeared to be responsible for the hydrodynamic sorting of particles along the estuary that resulted in denser, organic-poor particles being transported landward less efficiently. The elemental and isotopic compositions indicated that vascular C3 plants and estuarine algae were the major sources of the particulate organic matter of all the samples, without any significant contributions from salt marsh C4 vegetation (Spartina alterniflora) and/or marine phytoplankton. 2005 Elsevier Ltd. All rights reserved.

Impact of resuspended sediment on zooplankton feeding in Lake Waihola, New Zealand

Abstract: SUMMARY 1. Wind-induced sediment resuspension in shallow lakes affects many physical and biological processes, including food gathering by zooplankton. The effects of suspended sediment on clearance rate were determined for a dominant cladoceran, Daphnia carinata, and calanoid copepod, Boeckella hamata, in Lake Waihola, New Zealand. 2. Animals were incubated at multiple densities for 4 days in lake water containing different amounts of suspended lake sediment. Rates of harvest of major food organisms were determined for each sediment level (turbidity) from changes in net growth rate with grazer density. 3. Daphnia cleared all food organisms 7–40 lm in length at similar rates, but was less efficient in its removal of free bacteria, phytoplankton <7 lm, and large cyanobacterial filaments. Elevation of sediment turbidity from 2 to 10 nephelometric turbidity units (NTU) (63 mg DW L )1 added sediment) reduced Daphnia clearance of phytoplankton, heterotrophic flagellates and ciliates by 72–100%, and of amoebae and attached bacteria by 21–44%. Further inhibition occurred at higher turbidity. 4. Boeckella hamata removed microzooplankton primarily, rather than phytoplankton. The rate at which it cleared rotifers was reduced by 56% when turbidity was increased from 2.5 to 100 NTU. 5. In the absence of macrozooplankton, algal growth increased with sediment turbidity, suggesting that sediment also inhibits rotifer grazing. 6. As mid-day turbidity in Lake Waihola is ‡10 NTU about 40% of the time, sediment resuspension may play a major role in moderating energy flow and structuring pelagic communities in this lake.

The turbidity maximum zone of the Yenisei River (Siberia) and its impact on organic and inorganic proxies

Abstract: A general overview of the processes taking place in the summer mixing zone of the fresh Yenisei River water with the marine waters of the Kara Sea is given in this study, with special emphasis on the interaction between bulk (total suspended matter), inorganic (Fe, Mn) and organic (suspended organic carbon, suspended nitrogen) proxies Within the mixing zone, a zone of enhanced turbidity (maximum turbidity zone) was observed comparable to studies in other rivers Flocculation of particles due to changes in salinity and hydrography cause this maximum turbidity zone, and resuspension additionally enhances the turbidity in the near-bottom layers Organic matter behaves conservatively in the mixing zone in terms of its percentage of suspended matter It, however, undergoes degradation as revealed by amino acid data Inorganic, redox- and salinity-sensitive, proxies (Mn, Fe) behave non-conservatively Dissolved iron is removed at low salinities (<2) due to precipitation of iron oxyhydroxides and adsorption of manganese on suspended particles, enhancing the Mn/Al ratio of the suspended matter in the same zone At higher salinities within the mixing zone, Fe/Al and Mn/Al ratios of the suspended particles are depleted due to resuspension of sediment with lower Fe/Al and Mn/Al ratios Dissolved manganese concentrations are significantly higher in the near-bottom layers of the mixing zone due to release from the anoxic sediment All things considered, the Yenisei River mixing zone shows patterns similar to other world's rivers

The effect of chloride and orthophosphate on the release of iron from a cast iron pipe section

Abstract: “Colored water” resulting from suspended iron particles is a common drinking water consumer complaint which is largely impacted by water chemistry. A bench scale study, performed on a 90-year-old corroded cast-iron pipe section removed from a drinking water distribution system, was used to evaluate the effects of orthophosphate and chloride on iron release, color and turbidity. Experiments showed that an increase in chloride concentration of 100 mg/L significantly increased the concentration of iron released from the pipe section while the presence of orthophosphate at 3 mg/L decreased iron release. Chloride increased and orthophosphate decreased the water color and turbidity caused by the release of iron, but there was not a linear relationship with respect to the concentration of iron released. The control of chloride and orthophosphate concentrations is important in controlling the problem of colored water.

Granular Bed and Precoat Filtration

Abstract: Various filtration processes are used in potable water treatment. Granular bed and precoat filtration processes are described in this article, and focus is on descriptions of these processes and their particle removal efficiencies. Filtration processes are some of the major tools that are used to minimize microbial pathogens in drinking water, so the descriptions of their removal efficiencies contained herein emphasize their removal of microbes. This type of efficiency is characterized by a term called log removal, which is defined as log Co/C, where Co and C are the pathogen concentrations in a filter's inlet and outlet flows, respectively. Thus, a 1-log removal is equivalent to 90% removal. Current drinking water regulations target log removals of pathogens. Filter performance is also based on the amount of turbidity in the filtered water. Turbidity is a measure of water clarity. Turbidity reduces the aesthetic acceptability of drinking water and also shields pathogens from disinfectants that are added downstream of filters. Keywords: filtration; microbial pathogens; high-rate filtration; slow sand filtration; precoat filtration; Cryptosporidium

Impacts of goethite particles on UV disinfection of drinking water.

Abstract: A unique association between bacterial cells and small goethite particles (∼0.2 by 2 μm) protected Escherichia coli and Pseudomonas putida from UV inactivation. The protection increased with the particle concentration in the turbidity range of 1 to 50 nephelometric turbidity units and with the bacterium-particle attachment time prior to UV irradiation. The lower degree of bacterial inactivation at longer attachment time was mostly attributed to the particle aggregation surrounding bacteria that provided shielding from UV radiation.

Application of Polyelectrolyte in Turbidity Removal from Surface Water

Abstract: One of the most important treatment processes in surface water treatment plants is coagulation. Surface waters such as rivers and lakes contain suspended particles and turbidity. With the aid of coagulants, and by flocculation process, followed by sedimentation and filtration, these impurities can be removed from raw waters these days, besides conventional chemicals such as Alum and Ferric chloride, polymers are getting common. Polymers can be used as pretreatment and filter aids chemicals, also. There are some advantages in the usage of polymers, such as; higher sedimentation rate, lower price, better finished water quality, lower sludge volume produced, and a better sludge quality with respect to mineral coagulants. Of course some disadvantages are related to the polymers such as the monomers and residues in finished water which may be a health hazard. In this research, four different polymers for turbidity removal from raw waters were investigated. Raw water with turbidities of 200, 500, 700 and 1000 FTU were treated with optimum polymer dosage. The results showed that, polymers with small dosage can be used for water purification. In this regard it was found that Magnafloc LT27 has lowest dosage and better floc strength with respect to others.

Chlorophyll a and turbidity patterns over coral reefs systems of La Parguera Natural Reserve,Puerto Rico

Abstract: Studies of temporal and spatial changes in phytoplankton biomass and turbidity provide essential information on coral reef ecosystem function and health. Fluctuation of phytoplankton biomass responds to several factors including nutrient inputs, both anthropogenic and natural, while turbidity is mostly affected by sediment resuspension or transport from terrestrial systems. These parameters can be used as sentinels of significant environmental factors "modifying" coral reef systems. A chlorophyll a concentration (Chl a) and turbidity (Turb) in situ logger was installed at 10 stations from June 4 to July 7, 2003 in La Parguera Natural Reserve (Southwestern Puerto Rico) to assess short-term temporal and geographic variation in patterns of phytoplankton biomass and turbidity at pre-selected sites as part of an interdisciplinary long-term study. Average station Ch1 a variation was 0.17-1.12 microg 1(-1) and 0.2-23.4 NTU for Turb. Results indicate that the western near-coastal stations had higher levels of Turb and Ch1 a. The easternmost mid shelf station, Romero reef, was similar to coastal stations probably due to nutrient and suspended sediment inputs from a source external to our study area to the east, Guanica Bay. Comparisons between different sampling days indicate significant differences between days for most stations suggesting that one-time discrete sampling may not be representative of average water column conditions and illustrate the dynamic nature of coral reef systems. Further work is warranted to assess seasonal changes that integrate short-term (daily) variability in both Turb and Ch1 a.

Oscillation of a shallow lake ecosystem upon reduction in external phosphorus load

Abstract: A long-term study of eutrophication abatement in the Botshol Nature Reserve, the Netherlands, showed an intriguing response in this shallow lake. Beginning in 1988, the external nutrient load was reduced by hydrological segregation from agricultural areas and by chemical stripping of phosphorus from the water supply. A side effect of the hydrological segregation of Botshol from agricultural areas was an increase in chloride from 500 to 1000 mg l -1. In the first four years after the decrease in nutrient load, reductions were observed in phosphorus and chlorophyll a concentrations, as well as in the density of phytoplankton, zooplankton, and fish. Reduced phytoplankton density resulted in reduced turbidity and increased cover of Characeae from 2 to 80 %. Although the objective of re-establishing submerged macrophytes seemed to be attained, the clear water state appeared unstable. From 1993 onwards, the ecosystem alternated between turbid water with minor macrophyte production (1993-1995, 1999-2003) and clear water with abundant growth of aquatic plants (1996-1998). Phosphorus concentrations in Botshol also showed strong related fluctuations, despite a stable external phosphorus load.

The role of endogenous amphiphiles on the stability of virgin olive oil-in-water emulsions

Abstract: Stable virgin olive oil-in-water emulsions were prepared using total endogenous surface-active components derived from oil as emulsifying agents, and the interfacial properties of the emulsion droplets were examined. The amount of oil extracted into the aqueous buffer increased with buffer pH, with the most stable emulsions being formed at pH 7.5. Light microscopy of the emulsions revealed the presence of spherical droplets with diameters ranging from 1.5 to 3 μm. Their surface was negatively charged at pH 7.5, as confirmed by the effect of ions and polycations. Potassium chloride, Ca2+, and spermine induced rapid aggregation (as monitored by the turbidity change and by light microscopy), showing their maximal effect at 1 M, 4 mM, and 60 μM, respectively. Papain treatment of the emulsion particles rapidly induced particle aggregation, suggesting the destruction of stabilizing structural olive oil proteins. Unlike papain, treatment with phospholipase C did not result in an appreciable turbidity change. Treatment with soybean lipoxygenase slightly increased the turbidity of the emulsion. The interaction of linoleate-Tween 20 mixed micelles with emulsion droplets produced turbidity, which was maximal at a neutral pH, whereas interaction with proteolyzed and lipoxygenase-treated droplets induced both a significant increase in turbidity and a red shift to a different absorption maximum of the system as compared with those of the untreated emulsion.

Reducing Sediment and Phosphorus in Tributary Waters with Alum and Polyacrylamide

Abstract: The Salton Sea is the largest inland water body in California, covering an area of 980 km(2). Inflow to the Salton Sea (1.6 km(3) yr(-1)) is predominately nutrient-rich agricultural wastewater, which has led to eutrophication. Because internal phosphorus release from the bottom sediments is comparatively low and external phosphorus loading to the Salton Sea is high, reduction of tributary phosphorus is expected to reduce algal blooms, increase dissolved oxygen, and reduce odors. Removing both dissolved phosphorus and phosphorus-laden sediment from agricultural drainage water (ADW) should decrease eutrophication. Both alum and polyacrylamide (PAM) are commonly used in wastewater treatment to remove phosphorus and sediment and were tested for use in tributary waters. Laboratory jar tests determined PAM effectiveness (2 mg L(-1)) for turbidity reduction as cationic > anionic = nonionic. Although cationic PAM was the most effective at reducing turbidity at higher speeds, there was no observed difference between the neutral and anionic PAMs at velocity gradients of 18 to 45 s(-1). Alum (4 mg L(-1) Al) reduced turbidity in low energy systems (velocity gradients < 10 s(-1)) by 95% and was necessary to reduce soluble phosphorus, which comprises 47 to 100% of the total P concentration in the tributaries. When PAM was added with alum, the anionic PAM became ineffective in aiding flocculation. The nonionic PAM (2 mg L(-1)) + alum (4 mg L(-1) Al) is recommended to reduce suspended solids in higher energy systems and reduce soluble P by 93%.

Coagulation process for semi-aerobic leachate treatment using poly-aluminum chloride

Abstract: Sanitary landfill leachate is considered as heavily polluted industrial wastewater, which has extremely high pollution load that may pollute subsoil and ground water Special attention must be paid to its efficient treatment and disposal In this study, performance of coagulation and flocculation process was evaluated for semi-aerobic municipal solid waste leachate collected from Pulau Burung Landfill Site in Penang, Malaysia Poly-aluminum chloride (PAC) was used as coagulant which has not been a common coagulant in leachate treatment Effects of chemical and physical variables (concentration, pH, speed and time of rapid mixing and slow mixing) were examined by Jar-test experiments The optimum pH and dosage of poly-aluminum chloride were obtained as 75 and 19 g/L, respectively The most efficient rapid and slow mixing speeds were 80 for 45 seconds and 30 rpm for 15 minutes, respectively The optimum settling time was 30 minutes Results showed that 97% removal of colour, 61% reduction of chemical oxygen demand (COD), and almost complete removal of suspended solids (SS) and turbidity were obtained under optimum conditions