Discharges to Water

Aqueous discharges from limestone quarrying and processing do not, in general, present a significant environmental hazard. The most common contaminant is suspended matter, which can be removed by settling in sumps or slurry ponds. 

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Acrylonitrile is also readily soluble in water, and current total discharges to water via industrial effluents are low. Water contamination may also occur following a spill or near a chemical site. In water, acrylonitrile has little tendency to adsorb to sediment, but is subject to biodegradation by microorganisms. The rate and extent of degradation depend upon conditions and upon the time for microbial acclimation. Degradation may approach 100% under favorable circumstances, but may be inhibited by high concentrations of acrylonitrile. 

The most likely source of acrylonitrile in water is industrial discharges. Levels of acrylonitrile measured in the effluents from a variety of industrial sites (iron and stell factories, textile mills, chemical plants) have ranged from 20 to 4,700 ppb, resulting in concentrations in nearby rivers ranging from below detection limits to 4,300 ppb (EPA 1983c). Data collected under SARA indicated total discharges to water during 1987 were 0.9 metric tons (TRI 1988). 

A direct assessment of multimedia behavior is thus possible by examining the proportions of chemical found at steady state in the source medium and in other media. For example, when discharged to water, an appreciable fraction of the benzene is found in air, whereas for atrazine, only a negligible fraction of atrazine reaches air. 

If 1000 kg/h of benzene is discharged to water, as in the second row, there is predictably a much higher concentration in water (by a factor of over 2000). There is reaction of 546 kg/h in water, advective outflow of 134 kg/h and transfer to air of 320 kg/h with negligible loss to sediment. The amount in the water is 134000 kg thus the residence time in the water is 134 h and the overall environmental residence time is a longer 140 hours. The key processes are thus reaction in water (half-life 170 h), evaporation (half-life 290 h) and advective outflow (residence time 1000 h). The evaporation half-life can be calculated as (0.693 x mass in water)/rate of transfer, i.e., (0.693 x 133863)/320 = 290 h. Clearly, competition between reaction and evaporation in the water determines the overall fate. Ninety-five percent of the benzene discharged is now found in the water, and the concentration is a fairly high 6.7 x 10 g/m3, or 670 ng/L. 

The net result is that benzene behaves entirely differently when discharged to the three media. If discharged to air it reacts rapidly and advects with a residence time of 20 h with little transport to soil or water. If discharged to water it reacts and evaporates to air with a residence time of 140 h. If discharged to soil it mostly evaporates to air with a residence time in soil of 53 h. 

In this multimedia discharge scenario the overall residence time is 59 hours, which can be viewed as 60% of the air residence time of 19.7 h, 30% of the water residence time of 140 h and 10% of the overall soil residence time of 53 h. The overall amount in the environment of 59,000 kg is thus largely controlled by the discharges to water, which account for (0.3 x 133863) or 40,000 kg. 

An important number of these substances have an industrial origin. Some of them, like the pesticides, arrive intentionally in the environment and their use and release should be theoretically controlled. However, many of them have not been purposely produced as bioactive substances but more as components or additives of certain materials. Their significant growth in the chemical industry has not only been produced as a consequence of the discovery of new active principles in the pharmaceutical or pesticide area, but also because of the expansion of new technologies (electronics, containers, textiles, plastics, resins, foams, etc.), that require the development of new materials and substances with particular features. Most of these substances enter or are discharged to water and air sources without regulated controls. Wastewater treatment plants (WWTPs) are often not yet adapted to completely remove them, and therefore these new compounds can be found to some extent in wastewater effluents as well as in soil and sludge. 

No information concerning the release of 1,2-diphenylhydrazine to water was located in the literature. If discharged to water, detectable concentrations will probably persist for only a short time, since the half-life of (100 pg/L) 1,2-diphenylhydrazine in wastewater is about 15 minutes (Riggin and Howard 1979, 1982)... 

The principles of ecotoxicological quality classification based on the TU index are included in the 2002 recommendations of the Helsinki Commission (HELCOM). The classification applies to samples of treated effluents discharged to waters from industrial plants manufacturing chemicals,98 textiles,99 and pesticides.100 HELCOM recommends testing the acute toxicity of effluent samples using two of the four suggested indicator organisms (Table 9.6). 

The difference between decision making on the basis of a standard alone and on the basis of a standard plus other information can be described as one aspect of the direct versus the indirect model. In the direct model, action is defined exactly as that needed to secure compliance with the standard, for example, as permit conditions for discharges to water that are calculated to meet an environmental standard in a river. The classic cases here are substances like ammonia or cadmium in rivers and other mandatory standards in various European directives. 

Members of the European Council of Vinyl Manufacturers (ECVM), who account for 98% of production in the EU, have signed charters covering the production of VCM, S-PVC and E-PVC. This covers environmental standards for limits on emissions to air and discharges to water of VCM, EDC, HC1, ethylene, dioxin-like components and copper. VCM concentration in PVC is also strictly controlled (particularly for food/medical applications) (126). 

Where waste water is discharged into the sewers with the agreement of the local water authorities, a charge will normally be made according to the BOD value, and any treatment required. Where treated effluent is discharged to water courses, with the agreement of the appropriate regulatory authority, the BODS limit will typically be set at 20 ppm. 

It is very important to consider the pathways of radionuclides in the environment for design of the environmental monitoring program. Radionuclides enter the receiving environment via direct emissions to atmosphere, direct discharges to water bodies or releases from land burials of radioactive wastes. 

According to the TRI, an estimated total of 285 pounds of selenium metal and 45,066 pounds of selenium compounds were discharged to water from manufacturing and processing facilities in the United States in 1999 (TRI99 2001) (see Tables 6-1 and 6-2). The data listed in the TRI tables should be used with caution since only certain types of facilities are required to report. This is not an exhaustive list. 

Emissions to water discharges to water are reported as part of discharges to all media. 

Emissions to water no figures are given for discharges to water. 

The major sources of PCDD and PCDF in the Great Lakes basin are low temperature municipal waste and sewage sludge incinerators, and leachate from past disposal practices, some of which were designed to contain wastes (6). All of these current source types are the result of engineering treatment designed to reduce the concentration of these compounds in discharges to water bodies. 

Waste waters frequently contain dissolved metals, which may have to be removed or reduced to acceptable levels before discharge to water courses or sewage plants. 

Commercial quick- and hydrated limes are suitable for the treatment of waste water. In some situations, due consideration will need to be given to the permissible levels of trace elements in the lime, in the context of consent levels for discharges to water courses. 

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