Identify and locate potential areas of ground seeps in the watershed, specifically, leaks from local underground sewer lines situated near of along the river creeks and tributary streams in remote locations.
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Leakage from Sewer Lines
Effluent that leaks from sewer lines is generally untreated raw sewage. It may contain industrial waste chemicals. When leaking sewer lines are located deep underground below the biologically active portion of the soil, the sewage can enter groundwater directly. This can result in the introduction of chlorides, microorganisms, organics, trace metals and other chemicals that may cause disease and foul tastes or odors in drinking water (4).
Sewer leaks can occur from tree root invasion, soil slippage, seismic activity, loss of foundation due to washout, flooding and sewage back up, among other events (1). High pressure systems will push leaks to the soil surface where they can be easily detected by sight or odor. Systematic inspection of sewer lines, exclusion of hazardous waste, and adherence to modern construction and maintenance specifications are necessary preventative measures for protection of groundwater sources from sewer leaks(5).
Land Application of Partially Treated Waste Water and Municipal Sludge
Sludge is the residue of the chemical, biological, and physical treatment of municipal and industrial wastes (1). It can be applied to land as fertilizer or as fill. Land application is an alternative to incineration, which causes air pollution. Sludge usually contains concentrated organic matter, nitrogen, inorganic salts, heavy metals, and bacteria. It is a common practice to use partially treated waste water for fertilization, irrigation, and water supply recharge as an alternative to direct discharge into waterways. Waste water is also commonly stored in wells, holes, trenches, open pits and lagoons. Movement and percolation of waste water through the soil biologically and physically removes biodegradable substances, pathogenic organisms, and inorganic substances (4). The effectiveness of this treatment depends upon:
Processing or turnover time: Waste water must spend a sufficient amount of time on or within the soil to allow for filtration and biological processes to degrade the waste. If sufficient time is not allowed for these treatment processes to bring down contaminant levels before introducing waste water to a water system, contamination will occur.
Excess waste water and high concentrations of contaminants in the waste water: High concentrations of waste can take much longer to treat, especially when the consistency reaches that of a slurry or sludge. On the other hand, irrigation of soil with large quantities of waste water will saturate the soil and overload the biological degradation process. Excess untreated waste water can run off or percolate down to groundwater, causing contamination of drinking water supplies.
Level of biological processing: Lack of appropriate microbial activity can slow the degradation process or provide insufficient treatment. Bacteria which break down wastes without the use of oxygen, known as anaerobic bacteria, are very important in the process of breaking down nitrogen containing substances. Aerobic bacteria, which use oxygen, break down organic waste. Some of the breakdown products include water, carbon dioxide, methane gas, nitrates and other small organic and inorganic substances.
Water movement and abundance of vegetation: water movement and abundant vegetation can greatly enhance the degradation of waste water. From: http://extoxnet.orst.edu/faqs/safedrink/sewage.htm