Clay Turbidity Research Articles

Turbidity reduction in drinking water by coagulation-flocculation with chitosan polymers.

Turbidity reduction by coagulation-flocculation in drinking water reduces microbes and organic matter, increasing effectiveness of downstream treatment. Chitosan is a promising household water coagulant, but needs parameters for use. This study tested the effects of chitosan dose, molecular weight (MW), degree of deacetylation (DD), and functional groups on bentonite and kaolinite turbidity reduction in model household drinking water. Higher MW or DD produced greater reductions. Highest reductions were at doses 1 and 3 mg/L by MW >50,000 or >70% DD (residual turbidity <5 NTU). Higher doses did not necessarily continually increase reduction. For functional groups, 3 mg/L produced the highest reductions by lactate, acetate, and HCl, and lower reductions of kaolinite than bentonite. Doses where the point of zero charge was observed clustered around 3 mg/L. Chitosan reduced clay turbidity in water; effectiveness was influenced by dose, clay type, MW, DD, and functional groups. Reduction did not necessarily increase with MW. Bentonite had a broader effective dose range and higher reduction at the optimal dose than kaolinite. Chitosans with and without functional groups performed similarly. The best of the studied doses was 3 mg/L. Chitosans are promising for turbidity reduction in low-resource settings if combined with sedimentation and/or filtration.

Ventilation frequency in juvenile beluga sturgeon Huso huso L. exposed to clay turbidity

A 2-factorial experiment was conducted to investigate the effect of clay turbidity on ventilation frequency (VF) in juvenile beluga sturgeon Huso huso. Ninety fish (initial mean weight 27.2 ± 0.1 g) were exposed to six levels of turbidity (0.0, 2.5, 5.0, 10.0, 20.0 and 40.0 g clay/l) for three min. Then, the fish were gently transferred to a recovery tank and monitored to record the VF for 3 min. Results indicated that clay turbidity significantly affected the VF of the fish. The highest VF was observed in the first minute after the exposure. VF increased with increasing clay turbidity levels. In addition, the obtained results showed that VF of the beluga decreased through the time. Based on the result, it can be concluded that the beluga has the ability to adapt to clay turbidity in a short time; although they had an acute stress at first.

Modifications of nutrient regime, chlorophyll-a, and trophic state relations in Daechung Reservoir after the construction of an upper dam

Previous numerous studies on watershed scale demonstrated that the constructions of upper dams may influence the below dams due to modifications of flow regime and nutrient inputs. Little is known about how the dam constructions influence the downstream lakes or reservoirs in the regional scale. This study demonstrates how the construction of upper dam (i.e., Yongdam Dam) influences nutrient regime, trophic relations, and empirical models in Daechung Reservoir (DR). Yongdam Dam was constructed at the upstream region of DR in year 2000. The analysis of hydrological variables showed that inflow and discharge in the DR were largely reduced after the year 2000. The construction of upper dam construction also resulted in increases of water temperature, pH and conductivity (as an indicator of ionic content) in the DR. Empirical models of TP-CHL and N:P ratio-CHL suggested that stronger responses of CHL to the phosphorus were evident after the upper dam construction, indicating that algal production at a unit phosphorus increased after the upper dam construction. Mann-Kendall tests on the relations of N:P ratios to TN showed weak or no relations (t au = −0.143, z = −0.371, p = 0.7105) before the dam construction, while the relation of N:P ratios to TP showed strong in the periods of before- (tau = −0714, z = −2.351, p = 0.0187) and after the construction (t au = −0.868, z = −4.270, p = 0.0000). This outcome indicates that TP is key determinant on N:P ratios in the reservoir. Scatter Plots on Trophic State Index Deviations (TSIDs) of “TSI(SD) - TSI(CHL)” against “TSI(TP) - TSI(CHL)” showed that the dominance of clay turbidity or light limitation was evident before the upper dam construction [TSI(TP) - TSI(CHL) > 0 and TSI(SD) - TSI(CHL) > 0] and phosphorus limitation became stronger after the dam construction [(TSI(TP) - TSI(CHL) 0]. Overall, our analysis suggests that the upper dam construction modified the response of trophic components (phytoplankton) to the nutrients or nutrient ratios through the alteration of flow regime, resulting in modifications of ecological functions and trophic relations in the low trophic levels.

Alkalinity and Hardness: Critical but Elusive Concepts in Aquaculture

AbstractTotal alkalinity and total hardness are familiar variables in aquatic animal production. Aquaculturists—both scientists and practitioners alike—have some understanding of the two variables and of methods for adjusting their concentrations. The chemistry and the biological effects of alkalinity and hardness, however, are more complex than generally realized or depicted in the aquaculture literature. Moreover, the discussions of alkalinity and hardness—alkalinity in particular—found in water chemistry texts are presented in a rigorous manner and without explanation of how the two variables relate to aquaculture. This review provides a thorough but less rigorous discussion of alkalinity and hardness specifically oriented toward aquaculture. Alkalinity and hardness are defined, their sources identified, and analytical methods explained. This is followed by a discussion of the roles of the two variables in aquaculture, including their relationships with carbon dioxide, pH, atmospheric pollution, ammonia, and other inorganic nitrogen compounds, phytoplankton communities, trace metals, animal physiology, and clay turbidity. Liming and other practices to manage alkalinity and hardness are explained. Changes in alkalinity and hardness concentrations that occur over time in aquaculture systems are discussed. Emphasis is placed on interactions among alkalinity, hardness, water quality, and aquacultural production.

Clay- and algae-induced effects on biomass, cell size and toxin concentration of a brackish-water cyanobacterium

We studied if biomass, cell dimensions and microcystin concentration of the cyanobacterium Ana- baena sp. (strain BIR 257; recently also referred to as Dolichospermum) change in the presence of turbidity caused by clay and a eukaryotic green algal species. Anabaena sp. was incubated in experimental lab bioassays, with added clay and the chlorophyte Bra- chiomonas submarina. A control was established con- taining a single species of Anabaena sp. Biomass of Anabaena, given as carbon concentration increased in response to clay addition, suggesting that Anabaena was stimulated by lower light conditions whereas B. subm- arina was not. Cell lengths increased most likely as a response to lower light conditions. Dissolved toxin concentration decreased in treatments containing clay. Increased clay turbidity may favour the cyanobacterium Anabaena sp. over its eukaryotic competitors in the future Baltic Sea, especially in low-salinity estuaries.

Synthesis, Characterization and Floculating Properties of Coply(AM-DAC) in Water and Wastewater Treatment

A cationic polymeric flocculant was synthesized through solution polymerization. The polymerization was initiated by acrylamide and Aacryloxyethyltrimethyl Ammonium Chloride(DAC) monomers, and ammonium persulfate and sodium sulfite as redox initiation system. The copolymer obtained was characterized by Fourier-transform infrared (FTIR) spectroscopy. Its flocculating properties were evaluated by turbidity removal with clay suspensions, turbidity and COD removal with sewage using standard jar tests. The results demonstrate that the copolymer can be used as a kind of cationic polymeric flocculant in water and wastewater treatment.

Technical Note: A Constant-Volume Artificial Stream for Reducing Variation in Aquatic Process Measurements

This article describes the construction, operation, and assessment of a constant-volume artificial stream designed to control water quality and reduce variation to improve aquatic process measurements. The system was used to investigate suspended clay influence on phosphorus acquisition (load buffering) by lotic periphyton. Spatial and temporal heterogeneity represent the greatest sources of variation in the distribution and activity of aquatic biota in natural systems. Imposing experimental treatments simultaneously addresses temporal variation. Spatial variability is managed by controlling physical and chemical variables such as temperature, light, substrate, flow, and water quality. Controlling environmental conditions leads to reduced variation in biotic state, which improves the measurement of biotic processes. This artificial stream design minimizes water volume fluctuation, which facilitates solution manipulation and measurement and reduces environmental variation. A unique reservoir and valve arrangement compensates for evaporative water loss, allowing the operating water volume of individual stream units to be maintained (< 1%) over long periods. In pre-experiment assessments, mean total dissolved salts were maintained to within 3% of their initial concentration over a one-week period, and suspended clay turbidity was within 4.3% after some initial settling. During experimental use, artificial stream variation in periphyton biomass and phosphorus uptake was less than that reported from several natural streams.

Physiological and visual refuges in a metalimnion: an experimental study of effects of clay turbidity and an oxygen minimum on fish predation

Summary1. The effectivity of elevated clay turbidity and low‐oxygen concentration in the metalimnion as refuges for chaoborid larvae against fish predation was studied in experimental water columns.2. When 70–80 nephelometric turbidity unit clay turbidity was combined with 3–4 mg L−1 oxygen concentration, prey capture rate by fish (golden orfe Leuciscus idus) was reduced by 74% compared with the control treatment with no refuges. Oxygen and turbidity refuges alone did not significantly reduce the feeding rate.3. All fish in the control treatment dwelled in the metalimnion, but 36% of the fish in the low‐oxygen treatment and 23% of the fish in the turbidity treatment stayed in the epilimnion. In the combined treatment, 54% of the fish were in the epilimnion.4. The results demonstrated that a combination of moderately elevated turbidity and lowered oxygen concentration in the metalimnion is an effective protection against fish predation, while turbidity or oxygen refuge alone are much less effective.5. In the treatment with the combined refuge, oxygen concentration limited the time fish could spend in the metalimnion and turbidity affected the detection of prey through changes in reactive distance.6. Because of the combined effects of turbidity and oxygen refuges, planktivorous fish and phantom midge larvae may co‐occur in clay‐turbid lakes in high densities. Such situation is problematic for biomanipulation, which aims to enhance the grazing rate of zooplankton through reduction of planktivorous fish.

Effects of clay turbidity and density of pikeperch (Sander lucioperca) larvae on predation by perch (Perca fluviatilis)

Increased turbidity reduces visibility in the water column, which can negatively affect vision-oriented fish and their ability to detect prey. Young fish could consequently benefit from high turbidity levels that can provide a protective cover, reducing predation pressure. Perch (Perca fluviatilis) are commonly found in littoral zones of temperate lakes and coastal areas of the Baltic Sea. Pikeperch (Sander lucioperca) spawn in these areas, so perch is a potential predator for pikeperch larvae. We conducted laboratory experiments to test the predation of perch on pikeperch larvae at different turbidity levels (5-85 nephelometric turbidity units), densities of pikeperch larvae (2-21 individuals l(-1)) and volumes of water (10-45 l). The logistic regression showed that the probability of larvae eaten depended significantly on turbidity and volume of water in the bags, while density of larvae was not significant. However, because container size is known to affect predation, the data was divided into two groups based on water volume (10-20 and 25-45 l) to reduce the effects of container size. In either group, probability of predation did not significantly depend on volume, whereas turbidity was significant in both groups, while density was significant in larger water volumes. Thus, high turbidity impaired perch predation and protected pikeperch larvae from perch predation. Because density of larvae was also a significant factor affecting predation of perch, the dispersal of pikeperch larvae from spawning areas should also increase the survival of larvae.

Effects of clay turbidity and light on the predator–prey interaction between smelts and chaoborids

The effects of clay turbidity and light on the predator–prey interaction between planktivorous smelts (Osmerus eperlanus) and phantom midge (Chaoborus flavicans) larvae were studied by means of laboratory experiments. Irrespective of light intensity, fish-mediated mortality of chaoborid larvae was highest at intermediate turbidity (20 nephelometric turbidity units (NTU)). Increases in light intensity enhanced the feeding rate of smelts at very low light intensities. A regression model describing the dependence of smelt-mediated mortality of chaoborids on light intensity and turbidity was fitted to the data. The model suggested that turbidity exceeding 30 NTU combined with light intensity below 0.1 µE·m–2·s–1provides an efficient daytime refuge for chaoborids even in the presence of planktivorous smelts. In the field studies, the depth distribution of chaoborids followed the predictions of the model. The depth at which chaoborid density was highest depended on the existence and location of the thermocline, the densest swarms occurring beneath the turbidity maximum in the metalimnion. The smelts occupied water layers above the chaoborids, suggesting that the chaoborids used the steep turbidity gradient in the thermocline as a shelter against predation.

Effect of Low Turbidity and Algae on UV Disinfection Performance

It is well‐recognized that changes in ultraviolet (UV) absorbance or significant concentrations of amorphous biological wastewater solids in a water matrix can affect UV disinfection performance. However, the effects of low concentrations of drinking water particulates (turbidity) and algae on UV disinfection effectiveness are more poorly understood. This article presents the results of continuing studies at the University of New Hampshire (Durham) on the effects of particles on UV disinfection. The research was conducted in two phases of medium‐pressure UV collimated beam tests. The first phase compared the dose–response of seeded MS2 bacteriophage in waters with montmorillonite clay turbidity up to 12 ntu and algal content up to 42 μg/L as chlorophyll a (~42,000 cells/mL) to the dose–response of seeded MS2 in deionized water. The second phase compared phase 1 results with the inactivation of MS2 in the presence of naturally occurring turbidity in reservoir waters. Results indicated UV light was effective for inactivating MS2 in the presence of montmorillonite clay, algae, and naturally occurring turbidity in collimated‐beam testing.

Techniques to mitigate clay turbidity problems in fertilized earthen fish ponds

An experiment was conducted in fifteen earthen ponds at the Asian Institute of Technology (AIT), Thailand, during June to November 1998 to identify the source of clay turbidity, to evaluate several clay turbidity mitigation techniques and their effects on fish growth and water quality, and to find a suitable approach for turbidity mitigation during the rainy season. There were five treatments: (A) control; (B) covering upper 50 cm pond dikes with black plastic material to prevent turbidity from run-off (edge-covered); (C) covering pond bottoms with green manure (terrestrial weeds) to alter soil texture (weed-covered); (D) covering pond bottoms with small mesh (1 cm) net to prevent turbidity from fish disturbance (bottom-covered); and (E) covering pond dikes with rice straw (straw-covered). All ponds were fertilized weekly with chicken manure at a rate of 500 kg ha −1 (dry matter basis) supplemented with urea and triple superphosphate (TSP) to provide 28 kg N per ha per week and 7 kg P per ha per week. Sex-reversed all-male Nile tilapia ( Oreochromis niloticus) were stocked at two fish per square meter at a size of 19.0±1.0 g. Results showed clearly that clay turbidity was mainly from the run-off of pond dikes but not from fish disturbance of pond bottom during the rainy season and indicated that covering pond dike was effective in mitigating clay turbidity caused by the run-off in fish ponds. No significant differences of fish survival were found among all treatments. The straw- and weed-covered treatments resulted in significantly higher fish growth and yield. In contrast, the edge- and bottom-covered treatments did not increase fish yield, compared with the control. Covering pond dikes with rice straw not only reduces clay turbidity caused by run-off but also enhance Nile tilapia growth probably through microbial biofilm developed on the rice straw. Therefore, covering pond dikes with rice straw is a cost-effective technique for clay turbidity mitigation in fish ponds during the rainy season.

Calcite-amended horizontal roughing filtration for clay turbidity removal

Crushed basaltic river rock, calcite limestone, and calcite-amended basalt were three types of media tested in pilot-scale horizontal roughing filters pretreating slow sand filters fed from the Santiam River over 60-day periods. Montmorillonite and kaolinite clay challenge tests were conducted on ripened and unripened roughing filters to test performance at turbidities greater than 150 NTU, and clay removal trends were qualitatively examined using clay peak area ratios derived from X-ray diffraction. Enhanced montmorillonite removal was evident in the calcite roughing filter, but schmutzdecke growth was inhibited in the calcite-fed slow sand filter. The basalt, calcite and calcite-amended roughing filters in combination with slow sand filtration achieved 88.0, 95.3 and 99.6% clay turbidity removal, respectively, during the challenge tests. The slow sand filter pretreated with a calcite-amended roughing filter was the only configuration to produce effluent that complied with the 1 NTU regulatory requirement using influent of

The influence of turbidity on growth, feed conversion and survivorship of the Jamaica red tilapia strain

All male sex-reversed Jamaica red tilapia fry were reared in water at clay turbidity levels of 0, 50, 100, 150 and 200 mg/l over a 7-week period. It was found that there were significant decreases ( P<0.05) in weight gain and length increases as turbidity increased, but the differences at the higher levels of 100–200 mg/l were not significant. Specific growth rate (SGR) decreased and food conversion ratios (FCR) increased with increasing turbidity but the differences were not significant. Survivorship was negatively correlated with turbidity and the differences were significant ( P<0.05) at lower turbidities. It is suggested that clay turbidity levels in earthen ponds should be kept below 100 mg/l.

Evaluation of Transparency and Light Attenuation by Aquashade™

ABSTRACT Aquashade™, a colorant and dye registered by the US Environmental Protection Agency (USEPA) for use in aquatic environments to manage plant growth, does not reduce the visibility of water that otherwise would meet safe swimmming standards. This product was examined for its potential impact on underwater visibility in surface waters used for recreational swimming. Aquashade™ treatments of 0, 1, and 5 mg L−1 were evaluated in 3-m deep outdoor tanks containing reservoir water. Transparency and light attenuation were examined using a Secchi disk and an underwater photo synthetically active radiation (PAR) meter. In the first experiment, filtered lake water was used, while in the second, bentonite clay was added to provide a light transparency of approximately 1 m. In filtered lake water, Aquashade™ treatments (1 mg L−1 and 5 mg L−1) reduced light transparency by approximately 10% and 30%, respectively, but the transparency (272 and 194 cm, respectively) was well above typical international (100 cm) and state (33 cm) standards for safe swimming. In the trial with clay turbidity, the 1.0 mg L−1 Aquashade™ treatment was not significantly different in transparency when compared with the untreated reference, but the 5 mg L−1 treatment reduced transparency to 67 cm (31%). Aquashade™ absorbed light from 550 nm to 650 nm, with peak absorbance in the 630 nm range. Field measurements of Aquashade spectral attenuation matched that observed in the laboratory. While treatments at the allowable level of 1 mg L−1 will reduce transparency, the effect is small compared to inorganic or algal-induced turbidity that can occur in surface waters.

Clay turbidity and the relative production of bacterioplankton and phytoplankton

A comparison of phytoplankton with bacterioplanktonproduction as each ismodified by high concentrations of suspended clays ispresented. High clayturbidity caused light-limition of water columnphytoplankton production.However, the clay combined with DOC to form aggregateswhich supportedbacterioplankton production. Consequently,bacterioplankton production wasrelatively high at 42% of total small particleproduction in this lake.Bacterioplankton abundance and biomass was stronglycorrelated withphytoplankton chlorophyll a for most of the lake. Because of the association ofbacterioplankton with the clay-organic aggregates, DOCwas not a good predictorof bacterioplankton abundance or production. POC(primarily OC associatedwith clay) was correlated with bacterioplanktonabundance over most of thelake. Bacteria production was substrate limited asshown by much greaterbiomass-specific production at smaller bacteriapopulation sizes. Multipleregression analysis showed that specificbacterioplankton production wasprimarily governed by POC and secondarily by rates ofphytoplanktonproduction. Thus clay, because of light limitedphytoplankton production,negatively impacts bacterioplankton production yet atthe same time facilitatiesbacterial production by concentrating OC with theformation of the clay-organicaggregate.

Comparison of channel catfish, Ictalurus punctatus, and fathead minnow, Pimephales promelas, production and water quality among a polyculture and two monoculture systems

Production of channel catfish and fathead minnows was compared in three culture methods: two-pond polyculture (water interchanged between ponds containing catfish and those containing minnows), single-pond monoculture, and circulated-water monoculture. Improvement in catfish production and water quality appeared to be related to water movement in the circulated treatment and water movement and dilution in the polyculture treatment. Fathead minnow production in the polyculture treatment was comparable to low intensity commercial culture. High clay turbidity received from the catfish ponds may have depressed primary production, levels of plankton standing crops, and fish survival and growth in the fathead minnow polyculture treatment below that in the other two treatments.

Environmental Conditions and Channel Catfish Ictalurus punctatus Production under Similar Pond Management Regimes in Alabama and Mississippi

AbstractThis study was conducted to compare water quality and channel catfish production in earthen ponds located in two dissimilar physiographic regions of the southeastern United States and supplied with water of disparate quality. Ponds at Auburn, Alabama are on acidic Piedmont soils and filled with poorly mineralized runoff water; ponds at Stoneville, Mississippi are on slightly alkaline alluvial clays and filled with groundwater of high total alkalinity and hardness. Channel catfish were stocked at 8,750 fish/ha, fed daily, and provided nightly aeration in 0.04‐ha ponds at both sites. Ponds were managed as similarly as possible. Minimum daily water temperatures and pH were higher at Stoneville than at Auburn, and there were greater concentrations of suspended clay turbidity, dissolved inorganic phosphorus, total ammonia‐nitrogen, and nitrite‐nitrogen at Auburn than at Stoneville. The taxonomic composition of the phytoplankton community was broadly different between the two sites. Taste tests revealed off‐flavor in fish at both sites, but there were no significant differences (P &gt; 0.05) in flavor scores between sites. The quality of flavor was somewhat different between sites, and these differences in quality were thought to result from observed differences in the taxonomic composition of phytoplankton communities. All differences in water quality seemed to be directly or indirectly related to the dissimilarity in the quality of the water supply and soils at the two locations. Although some water quality variables differed between sites and changed over time at both sites, environmental conditions never deteriorated enough at either site to cause serious stress or mortality in fish. There were no significant differences (P &gt; 0.05) in average net fish production, survival, weight of individual fish at harvest, or feed conversion ratios. Average net fish production and feed conversion ratios, respectively, were 4,905 kg/ha and 1.27 at Auburn and 5,286 kg/ha and 1.27 at Stoneville. The results of this study demonstrate the need for site‐specific investigations when conducting certain types of aquaculture research.

Tilapia yield improvement through maintenance of minimal oxygen concentrations in experimental grow-out ponds in Honduras

Tilapia yields and water quality were compared in 1000-m 2 grow-out ponds that were unaerated, or aerated beginning at 10 or 30% of oxygen saturation. Tilapia yield and individual final size were significantly greater in aerated ponds than in unaerated ponds, but there were no significant differences between levels of aeration. Treatment means of organic-N, total P. chlorophyll a, net primary productivity, and total volatile solids were not significantly different. However, aeration caused higher clay turbidity as indicated by significantly higher total fixed solids and lower Secchi disk visibility in aerated treatments. Maintenance of oxygen above minimal levels augmented tilapia yields, but additional research is needed to make aerator use in tilapia culture more efficient and profitable.

Influence of site and season on water quality and tilapia production in Panama and Honduras

Data from 2 years of standardized experimental protocols in Panama and Honduras were analyzed to ascertain the influence of site and season on production of Oreochromis niloticus in earthen ponds. In Experiment 1, ponds were fertilized every 2 weeks with trip le superphosphate at 4 kg P 2O 2/ha, and were monitored to establish baseline of edaphic, climatic and fish production data. In Experiment 2, ponds were fertilized weekly with chicken litter at 125, 250, 500, or 1000 kg total solids/ha. Both experiments were repeated during wet and dry seasons at each site. Honduras ponds were more alkaline and higher in phosphorus than Panama ponds that were excavated in acidic soils. However, Honduras ponds were turbid with clay. The net result of acidic, nutrient-poor soils in Panama and clay turbidity in Honduras was low biological productivity at both sites for inorganically fertilized ponds. Primary productivity and net daily fish yield significantly increased with increasing chicken litter application ( P < 0.05). Primary productivity, chlorophyll a, and net daily fish yield were similar at both sites in ponds fertilized weekly with chicken sitter at 125–500 kg/ha; however, at the highest fertilization rate, primary productivity, chlorophyll a, and net daily fish yield were 57, 29, and 37% greater in Panama than in Honduras. Higher fish yield was significantly correlated with higher chlorophyll a and primary productivity. Lower primary production and net daily fish yield in Honduras were attributed to light limitation by clay turbidity.