Freshwater systems indicators

Copper (II) is present in natural waters in a variety of chemical forms. Syl-va [246] indicated that the following species are found in freshwater systems Cu2+ Q1CO3 01(003)2 O1HCO3 CuOH+ Cu2(OH)2+ CuCl+. It was also found that Cu2+ can be removed completely from aquatic systems by precipitation as Cu(OH)2, O1CO3, and Cu(0H) (C03)i /2. 

Oxidation rate constant k, for gas-phase second order rate constants, kOH for reaction with OH radical, kNG3 with N03 radical and kG3 with 03 or as indicated, data at other temperatures see reference k0H(calc) = 1.8 x to 12 cm3 molecule-1 s 1 at room temp. (SAR, Atkinson 1987) tropospheric lifetime x(calc) = 8-17 d, based on kOH(calc.) = (1.4 - 2.9) x io 12 cm3 molecule-1 s 1 for dichlorobiphcnyls at room temp. (Atkinson 1987) koH.(aq.) = 7.9 x 109 dm3 mol-1 s-1, PCB in Aroclor 1242 mixture, oxidized by hydroxyl radicals generated with Fenton s reagent in aqueous solutions at 25°C, half-lives range from 4-l 1 d in freshwater systems, 0.1-10 d in cloud water, > 1000 d in oceans for PCBs with as many as 8 chlorines (relative rate method, Sedlak Andren 1991) tropospheric lifetime x(calc) = 3.4-7.2 d, based on the experimentally determined gas-phase reaction kOH(exptl) = (2.0-4.2) x io-12 cm3 molecule-1 s-1, and the calculated kOH(calc) = (1.4 - 3.1) x io-12 cm3 molecule-1 s 1 at room temp. (Kwok et al. 1995)... 

Appendix A contains a materials selection guide for aerated freshwater systems. As indicated in Note 27 of Appendix A, in freshwater systems, admiralty brass should be limited to a maximum pH value of 7.2 from ammonia and copper-nickel alloys and should not be used in waters containing more sulfides than 0.007 mg/L The materials selection guide is also satisfactory for seawater, although pump cases and impellers should be a suitable duplex stainless steel or nickel-aluminum-bronze (properly heat treated). Neoprene-lined water boxes should be considered. For piping, fiber-reinforced plastic (up to 150 psi [1,035 kPa] operating pressure) and neoprene-lined steel should also be considered. Titanium and high-molybdenum SS tubes should be considered where low maintenance is required or the cost can be justified by life expectancy. 

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