Freshwaters controls

Chloride. Chloride is common in freshwater because almost all chloride salts are very soluble in water. Its concentration is generally lO " to 10 M. Chloride can be titrated with mercuric nitrate. Diphenylcarbazone, which forms a purple complex with the excess mercuric ions at pH 2.3—2.8, is used as the indicator. The pH should be controlled to 0.1 pH unit. Bromide and iodide are the principal interferences, whereas chromate, ferric, and sulfite ions interfere at levels greater than 10 mg/L. Chloride can also be deterrnined by a colorimetric method based on the displacement of thiocyanate ion from mercuric thiocyanate by chloride ion. The Hberated SCN reacts with ferric ion to form the colored complex of ferric thiocyanate. The method is suitable for chloride concentrations from 10 to 10 M. 

Examination of the influence of agriculture on phosphorus input to freshwater requires careful study to determine the most appropriate control strategies. The influence will vary in relation to whether the phosphorus is dissolved or particulate. Also, we know that variation in the input of particulate and dissolved... 

Dispersed Noninhibited Systems. Drilling fluid systems typically used to drill the upper hole sections are described as dispersed noninhibited systems. They would typically be formulated with freshwater and can often derive many of their properties from dispersed drilled solids or bentonite. They would not normally be weighted to above 12 Ib/gal and the temperature limitation would be in the range of 176-194°F. The flow properties are controlled by a deflocculant, or thinner, and the fluid loss is controlled by the addition of bentonite and low viscosity CMC derivatives. 

Quebracho-treated freshwater muds were used in drilling at shallow depths. The name of red mud comes from the deep red color imparted to the mud by quebracho. Muds treated with a mixture of lignite and quebracho, or a mixture of alkaline organic polyphosphate chemicals (alkaline-tannate treated muds), are also included in the quebracho treated muds. The quebracho thinners are very effective at low concentrations, and offer good viscosity and filtration control. The pH of red" muds should be 8.5 to 10 mud temperature should be lower than 230°F. 

Lignosulfonate freshwater muds contain ferrochrome lignosulfonate for viscosity and gel strength control. These muds are resistant to most types of drilling contamination due to the thinning efficiency of the lignosulfonate in the presence of large amounts of hardness and salt. 

Seawater muds are composed of bentonite, thinner (lignosulfonate or lignosulfonate and lignite), and an organic filtration control agent. The typical formulation of a seawater mud is 3.5 Ib/bbl of alkali (2 Ib/bbl caustic soda and 1.5 Ib/bbl lime), 8 to 12 Ib/bbl of lignosulfonate, and 2 to 4 Ib/bbl of bentonite to maintain viscosity and filtration. Another approach is to use bentonite/thinner (ligno-sulfonate)/freshwater premix, and mix it with seawater that has been treated for hardness. This technique will be discussed in the saturated saltwater muds section. 

A modified saturated saltwater mud is prepared with bentonite clay by a special technique. First, bentonite is hydrated in freshwater, then treated with lignosulfonate and caustic soda. This premix is then mixed with saltwater (one-part premix to three-part saltwater). The mixture builds up a satisfactory viscosity and develops filtration control. Thinning of the mud is accomplished by saltwater dilutions additional premix is required for viscosity and water loss control. 

Salts are sometimes added to drilling muds to obtain certain desired mud characteristics. They can also enter the drilling fluid through contamination by addition of makeup water, formation-fluid inflow, and drilled formations such as salt domes, gypsum or anhydride formations. In freshwater systems, if salt contamination reaches undesirable levels, the following methods should be considered for control. 

Acid precipitation, or acid rain, can causes significant impacts on freshwater, coastal, and forested ecosystems (e.g.. Likens et ai, 1996). Both NOi", from NO emissions, and SO from SO2 emissions contribute significantly to acid rain. The relative ratio of SO /NOf in precipitation will be substantially determined by the regional emissions of SO2/NO3. In developed countries, uncontrolled combustion of coal and high-sulfur fuel oil led to significant emissions of SO2, relative to NO Due to strict control of smokestack SO2 emissions in some regions and increasing NO emissions from automobiles, the relative contribution of NOi is expected to increase (Sirois, 1993 Mayewski et ai, 1990). 

Apart from the importance of OP resistance in pest control, ecotoxicologists have become interested in the development of resistance as an indication of the environmental impact of insecticides. Thus, the development of esteratic resistance mechanisms by aquatic invertebrates may provide a measure of the enviromnental impact of OPs in freshwater (Parker and Callaghan 1997). 

Mason RP, Laporte J, Andres S. 2000. Factors controlling the bioaccumulation of mercury, methyhnercury, arsenic, selenium, and cadmium by freshwater invertebrates and fish. Arch Environ Contam Toxicol 38 283-297. 

The martensitic alloys contain 12 to 20 percent chromium with controlled amounts of carbon and other additives. Type 410 is a typical member of this group. These alloys can be hardened by heat treatment, which can increase tensile strength from 550 to 1380 MPa (80,000 to 200,000 Ibf/in ). Corrosion resistance is inferior to that of austenitic stainless steels, and martensitic steels are generally used in mildly corrosive environments (atmospheric, freshwater, and organic exposures). In the hardened condition, these materials are very susceptible to hydrogen embrittlement. 

Boric acid can form complexes with hydroxyl compounds. The control of the delay time requires control of the pH, the availability of borate ions, or both. Control of pH can be effective in freshwater systems [17]. However,... 

Quevauviller Ph, Vercoutere K, Griepink B (1992b) Certified reference materials (CRMs 398 and 399) for the quality control of major element determination in freshwater. Mikrochim Acta 108 195-204. 

Adapted from Brungs, W.A., R.A. Carlson, W.B. Horning II, J.H. McCormick, R.L. Spehar, and J.D. Young. 1978. Effects of pollution on freshwater fish. Jour. Water Pollut. Control Fed. 50 1582-1637. 

Copper compounds are used routinely and widely to control freshwater snails that serve as intermediate vectors of schistosomiasis and other diseases that afflict humans (Hasler 1949 NAS 1977 Rowe and Prince 1983 Winger etal. 1984 Al-Sabri etal. 1993). These compounds include copper sulfate, copper pentachlorophenate, copper carbonate, copper-tartaric acid, Paris green (copper arsenite-acetate), copper oxide, copper chloride, copper acetyl acetonate, copper dimethyl dithiocar-bamate, copper ricinoleate, and copper rosinate (Cheng 1979). Also, many species of oyster enemies are controlled by copper sulfate dips. All tested species of marine gastropods, tunicates, echinoderms, and crabs that had been dipped for 5 seconds in a saturated solution of copper sulfate died if held in air for as little as a few seconds to 8 h mussels, however, were resistant (MacKenzie 1961). 

Cuttlefish, Sepia officinalis-, eggs 4 (control), 50, 100, or 200 pg/L for 8 weeks Freshwater snail, Thiara tuberculata Dose-dependent decrease in hatching time and survival no external malformations 51... 

Freshwater-adapted exposure for 37 days experimentals (15 pg/L) vs. controls (5 pg/L) values in mg/kg DW tissue... 

Eggs were exposed in freshwater to 4 pg Ag/L for 14 days prior to hatch. After hatching, larvae were exposed to 4 pg Ag/L in salt water for 14 days during yolk-sac resorption. Fry were then transferred to uncontaminated salt water and fed a high metals diet for 64 days (diet At end of study, experimentals had a small, but significant, decline in survival. Just prior to transfer to uncontaminated salt water, experimentals contained 62 pg Ag/kg whole body DW vs. 4 in controls. After 64 days in uncontaminated salt water, whole alevins contained 18 pg Ag/kg DW vs. 4 in controls 29... 

---