ACID Plumbing engineers, inspectors and contractors have a responsibility to make owners aware of environmenta/ Jaws as we/1 as the minimum requirements ot the plumbing code. Discharging acid wastes into a sanitary sewer and ignoring codes and regulations for hazardous waste discharge can result in a liability for facility owners and even engineers. in the past, diluting acid wastes with water was the primary form of treatment. Most model plumbing codes along with federal, state and local environmental regulations require net neutralization or dilution of acid wastes. Many local authorities are requiring monitoring of acid wastes, or at least sampling stations, in manholes on the building sewer. Code requirements Both model plumbing codes require some form of treatment. The 1996 edition of the Uniform Plumbing Code (UPC) requires treatment of chemical or industrial wastes in Section 811.0. The 1995 edition of the lnternational Plumbing Code (IPC) requires a neutralization device tor corrosive wastes in Section 804.1. Both model codes have language stating chemical wastes shall not injure the sanitary drainage system. The UPC has exceptions tor minor installations including photographic or x-ray dark rooms tor small resecarch or control labs where minor amounts of effluent can be adequately diluted. The IPC requires dilution devices to be provided with an automatic supply of diluting water of sufficient supply to make the waste noninjurious to the sanitary drainage system. in either case, diluting the acid wastes could use significant amounts of water, and some form of monitoring of the effluent is needed according to many environmental regulations. Both model plumbing codes require acid-resistant piping materials tor the acid waste and acid vent systems. These systems should be completely independent of the 94 UYGULAMA WASTE SYSTEMS sanitary drain age system until after the acid dilution or neutralization basin. Typical acid waste piping meterials are polypropylene, glass or high-silicon cast iron. During the early stages of a project a code survey should be done to determine which codes are applicable to your project. Environmental regulations often exceed requirements in the plumbing code. Plumbing engineers, inspectors and contractors have a responsibility to make owners aware of the minimum requirements of the plumbing code and the environmental laws. Engineers and contractors should protect their clients from liabilities, such as lawsuits, which can result from discharges of chemicalbearing wastes into public sewers and eventually the environment. Sources of acid waste Acid wastes typically are generated by discharges from laboratories, hospitals, shools, universities, industrial plants, x-ray and photo developing units, battery recycling or charging facilities, paper milis, metal plating operations, semiconductor manufacturing facilities and other industrial processes. Acid producing processes are growing in complexity and volume. Recent water conservation legislation has caused water flow rates in plumbing systems to decrease. The result could be that acid waste becomes more concentrated in the public sewer systems, making dilution a less desirable option. The need to protect our public sewer systems and natural resources is becoming greater. Engineers should consider monitoring waste effluents when the conditions dictate large amonuts of acid waste effluents Sometimes engineers choose to not use an acid neutralization or dilution basin when mild acids or caustics are discharged, believing only small amounts of these materials will go down the drain. They often are unaware that mild chemicals. For example, strong acids attack metal Ron GEORGE & Smith HINCHMAN piping systems immediately, and cause the metal pipe to form precipitant coatings such as ferric chloride or similar precipitates that protect the piping system from further attach. in contrast, mild acids attack a metal piping system a little at a time and the acids dissolve through the piping components more quickly. This happens because the mild acids do not allow precipitant coatings to form and protect the pipe. Dilution and neutralization For years the primary method of treating acid wastes was to dilute the waste before it entered the sanitary drainage system. Dilution is the process where acid wastes are rendered harmless by using massive amounts of water, the universal solvent. Mixing water with acid waste dilutes the effluent to a point where chemicals in the waste are rendered impotent. On the other hand, it too much water is introduced too rapidly into the treatment tank, the effluent can be washed out of the tank before it has a chance to be neutralized or diluted. The amount of dilution can be measured in numerical terms by measuring the positive hydrogen ion level, or pH Neutral liquids, such as water, have apH of 7. The lower the pH number, progressing from 6.99 to O, themore acidic the solution. The higher the pH, from 7.01 to 14, the more alkaline the solution. (See table 1.) Neutralizing acid waste is the process where chemical- bearing wastes can be rendered harmless with the use of neutralizing chemicals, usually calcium carbonate. This process makes the acid waste neutral or non-acidic before it leaves the neutralization basin. Both systems are constructed basically the same; the fixtures, piping and a dilution or neutralization basin are constructed of acid-resistant materials. The only difference is that the neutralization basin is filled with limestone chips consisting primarily of
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