Sewer

this chapter presents some studies concerning the evolution of raw wastewater quality in sewers and, second, the effect of some treatment processes. Two examples of treatment plants are then presented, before a synthesis leading to the proposal of a wastewater classification. 

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Reinforced furan resias have been used for many years in process piping and in underground sewer or waste-disposal systems. With a wide range in pH acceptability and good solvent resistance, furan piping has been a logical choice for many services. 

Disposal of waste or spilled caustic soda must meet all federal, state, and local regulations and be carried out by properly trained personnel. Accidental spills of dry caustic are shoveled and flushed with water caustic soda solutions must be diluted and neutralized with acid before discharging into sewers. Dilute acetic acid may be used to neutralize final traces of caustic. 

A number of flume designs have been created specifically for use in partially fiUed circular conduits such as sewers. These are available in molded fiber glass and can be lowered through a manhole if required. As with all open-channel head-area meters, flumes must be sized to prevent submergence of the restriction. 

Several special forms of electromagnetic flow meters have been developed. A d-c field version is used for Hquid metals such as sodium or mercury. Pitot and probe versions provide low cost measurements within large conduits. Another design combines a level sensor and an electromagnetic meter to provide an indication of flow within partially full conduits such as sewer lines. 

Storage areas for maintenance, janitorial, and other service organizations must be provided. Safety items such as fire extinguishers, firehose cabinets, safety hoops on permanent ladders, guard rads, shielding for acid pumps, clearance for electric panel boards, etc, are needed. Manholes and cleanouts for sewer pipes within the facility as well as in the landscape and parking areas should be provided. 

Waste Disposal. Because of its low Boiling poiat and high, toxicity, measures must be taken to prevent the entrance of phosgene iato drains or sewers. If recycle of phosgene is not feasible, phosgene waste can be handled by one of the decomposition methods mentioned above, ie, caustic scmbbiag, moist activated carbon towers, or combustion. 

Shipments of concrete pipe in 1990 had a value of > 1.6 billion dollars. Much of this piping was for storm and sanitary sewers, culverts, and irrigation piping. Pressure piping sales were close to 300 million. There are a large number of manufacturers of concrete pipe since much of the pipe is produced reasonably close to the point of use. 

When considering taxes, all types need to be considered initial fees, capital value, corporate rate, personal income tax, sales tax, property tax, unemployment insurance, workmen s compensation, and nuisance tax. During the constmction phase, several types of taxes may be levied. These include building permits, special fees, assessments, and sewer connection fees. 

Local Site Condition Evaluation. In addition to visiting the site, drawing up a contour map and geology reports, acquiring sod-bearing information, and a knowledge of boundaries, setbacks, local requirements, utdity tie-in locations, sewer connections, access to roadways, pipelines, radroads, etc, may be needed to make a fliU assessment. 

Uocation and adequay of drains, spills, basins, dikes, and sewers... 

Waste facihties should be designed to prevent explosions in sewer systems and typically are comprised of suitable traps, vents, clean-outs, collecting chambers, etc. Flammable gas detectors are installed in sewers to warn of ha2ardous concentrations, and inert gas blanketing of closed process sumps generally is advisable. 

Sewer Disposal. Photoprocessing and printing wastes tend to be aqueous solutions that ate combined with other plant effluents and sent to the local sewer plant for treatment. The parameters of concern include silver, pH, and biological oxygen demand (BOD). BOD is a measure of how well a waste material degrades in the environment. Lower values ate preferred. Silver-bearing waste streams ate typically treated on-site, and the treated effluent is released to the drain. The printer usually receives a small cash credit for silver recovered. 

There are two reasons why the concentration of quaternaries is beheved to remain at a low level in sewage treatment systems. First, quaternaries appear to bind anionic compounds and thus are effectively removed from wastewater by producing stable, lower toxicity compounds (205). Anionic compounds are present in sewer systems at significantly higher concentrations than are cations (202). Second, the nature of how most quaternaries are used ensures that their concentrations in wastewater treatment systems are always relatively low but steady. Consumer products such as fabric softeners, hair conditioners, and disinfectants contain only a small amount of quaternary compounds. This material is then diluted with large volumes of water during use. 

Protection of the environment from uncontroHed radioactive release is also a consideration in the use of radiotracers. The quantity and concentration of radionucHdes that may be discharged into sewer systems is limited by regulations of the Nuclear Regulatory Commission (NRC). 

For low pressure pipelines that have ports open to the atmosphere, eg, sewers or closed effluent culverts, samplers are designed to sample through manholes. In a typical system, the Hquid is lifted through a suction line into the sampling chamber under vacuum. When filled, the vacuum shuts off, and the sample drains into a sample jar. A secondary float prevents any Hquid from reaching the vacuum pump. The suction line then drains by gravity back to the source. 

An Assessment of Automatic Sewer Flow Samplers, PB-25,987, U.S. Dept, of Commerce, Washington, D.C., 1976. 

Transportation and Disposal. Only highly alkaline forms of soluble sihcates are regulated by the U.S. Department of Transportation (DOT) as hazardous materials for transportation. When discarded, these ate classified as hazardous waste under the Resource Conservation and Recovery Act (RCRA). Typical members of this class are sodium sihcate solutions having sihca-to-alkah ratios of less than 1.6 and sodium sihcate powders with ratios of less than 1.0. In the recommended treatment and disposal method, the soluble sihcates are neutralized with aqueous acid (6 Af or equivalent), and the resulting sihca gel is disposed of according to local, state, and federal regulations. The neutral hquid, a salt solution, can be flushed iato sewer systems (86). 

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