Water Quality Problems

Where air stripping is used in conjunction with other water treatment processes such as flocculation, the positioning of the air stripper in the supply flow stream may be important. Positioning of the stripping tower downstream of the flocculation unit has been accomplished successfully where strict control over the quantities of floe particles released into the water stream has been maintained. 

Two approaches are used to prevent precipitation of inorganics in the air stripper. A chelating system introduces an agent that binds with the inorganic material that would otherwise precipitate. Citric acid is often used to keep iron in solution as it passes through the air stripper. A second approach is the use of a sequestering agent that reduces surface tension within the system and thereby prevents encrustation. 

The most common method for reducing the numbers of these organisms is by chlorination of the influent water. Periodically, it may be necessary to clean and disinfect the air stripper by shocking the tower with acid or chlorine, or by surging the tower with peroxide. Routine inspections and cleaning of the air stripper must be considered normal maintenance and a part of the operational expense. In addition, corrosional effects and an increase in the formation potential of THMs (trihalomethanes chloroform and bromoform) may result from chlorination. 

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In general, the role of the water quality engineer and scientist is to analyze water quality problems by dividing each case into its principal components. These are ... 

The goals of this chapter do not include a "state of the art" literature review which would be appropriate for a more in-depth discussion of one particular problem area. Rather the intent is to illustrate mechanistic approaches to river quality assessment using the three globally relevant water quality problem areas discussed in the previous chapter dissolved oxygen depletion, erosion/deposition, and potentially toxic trace elements. The information provided does not include all rationale, methology or approaches used in the study as this is beyond the scope of the chapter. Additional general information on application of the intensive river quality assessment approach in the Willamette River basin may be found elsewhere (4-9, 11-14, 17). 

This chapter aims to review current knowledge on the effects of wastewater treatment plant (WWTP) inputs (as major nutrient point sources) on stream nutrient dynamics, with major emphasis on nutrient loads and in-stream nutrient retention, and to discuss its implications within the context of actual and future scenarios of water scarcity conditions. Following this introduction, the second section of this chapter describes water quality problems associated with wastewater inputs from urban areas and how they are faced within the context of increasing urbanization across the world and its higher impact on water availability. In the third section, we... 

Lawns also represent an urban ecological problem on a vast scale. In the United States, the chemicals of lawn maintenance-including dichlorophenoxy-acetic acid (2,4-D), glyphosate, diazinon, and dicamba-are significant contributors to nonpoint source water quality problems that continue to elude solution almost 30 years after the passage of the Clean Water Act. Lavm pesticides are applied on a scale to rival agricultural toxins 23% of the total 2,4-D applied in the United States is used on lawns 22% of glyphosate, 31% of chlorpyrifos, and 38% of dicamba used nationally is applied to home lavms. ... 

Effluent waters from denitrification reactors, while free of nitrate, may have other water quality problems. During bench-scale testing, it was found that process effluent contained high chemical oxygen demand (COD), total suspended solids (TSS), and turbidity. Dissolved oxygen (DO) levels were low, and odor was caused by the presence of measurable amounts of hydrogen sulfide. 

A re-evulualinn of the water quality problem has revealed that surface water resources, rather than groundwater resources, are at higher risk of contamination from agricultural chemicals. 

Land disturbance and exposure of buried geologic strata to the open environment leads to sulfide oxidation (if present) and, as a consequence, water-quality degradation of runoff. For water-quality-control purposes, sedimentation ponds required by law are used as water treatment basins. Often, the pH of such basin waters is below 6, and the concentration of heavy metals is above acceptable levels. Water treatments include neutralization and removal of heavy metals as precipitates. Similar water-quality problems arise from other industrial sources, including heavy steel industries, electronics, food processing, mineral processing, and waste-disposal leachates. This portion of the chapter deals with some of the chemical agents used for neutralization purposes and some of their limitations. 

Alternatives most frequently considered for taste and odor removal include breakpoint chlorination, aeration, ozonation, and oxidation with chlorine dioxide or potassium permanganate. None of these technologies have been found to approach the activated carbon adsorption process iri terms of effective treatment for this particular water quality problem. Another alternative is sorption onto other solids such as bleaching clays, synthetic resins or manganese dioxide. A brief summary of the advantages, disadvantages and cost factors associated with adsorption and alternative treatments for removal of tastes and odors... 

UKWIR (2000) Technical Guidance for the Implementation of Direct Toxicity Assessment (DTA) for Effluent Control Addressing Water Quality Problems in Catchments where Acute Toxicity is an Issue. Report TX02B 217. 

The Middle East has severe, generaUy transboundary, air and water quality problems. 

ESCAP. (1998). Sources and Nature of Water Quality Problems in Asia and the Pacific. New York, United Nations, 164 pp. 

H. O. Banks and J. H. Lawrence, Water Quality Problems in California, Transactions of the American Geophysical Union, vol. 34, no. 1, pp. 58—66, 1953. Although chlorinated solvents are not specifically mentioned in the paper, they are members of the broader category of organic solvents. See Amter and Ross, Discussion of Rivett and Clark. ... 

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