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Technical Description lute of the return pump, is returned to the aeration chamber by the sludge return pump. The re- maining sludge and floatables, now settled on the tank bottom, are transferred back to the aera- tion chamber during the MILT pump overrun on the next batch cycle. After settling has occurred, the microprocessor initiates the effluent transfer pump (SNT), which transfers the treated effluent into the disinfection chamber. During the effluent transit, ozone is injected into a distribution manifold in the bottom of the ozone contact chamber. Ozone injection continues for 40 minutes after the chamber is filled. NOTE: Following are the reasons we do not recommend the use of chlorine as a disinfec- tant for the Castillo Estates Project which will utilize a sub-surface irrigation/disposal con- cept for effluent disposal. Some states are currently passing legislation preventing the use of chlorine as a disinfectant in both wastewater and freshwater applications. This is done for reasons of health for both the environment and living creatures. A simplified explanation of the reasoning follows: In order to ensure that enough chlorine has been applied to achieve a maximum pathogen kill, there must be a measurable amount of chlorine in the system discharge. In the case of water-body discharge, this small amount is deadly to virtually all natural life-forms in the water. In the case of land-sub-surface discharge, over a period of time chlorine will build up to a level high enough to cause conversion of soil-bound minerals to salts, which are not only toxic to the soil but will leach out into groundwater supplies. These conversions are expressed as: CI + Na —> NaCl CI + K —K CI Cl + Mg —> MgCl2 CI + Ca —> CaC12 In addition, the factors that affect the bacterial and virucidal efficiency of chlorine can vary widely on a seasonal basis from day to day and from daytime to nighttime. In fact, marked variations have been shown in samples taken from the same effluent stream at intervals as short as one hour. The source of chlorine may take many forms. The important thing to remember is that chlorine derived from almost any source forms hypochlorous acid in dilute solutions used for wastewater disinfection. Hypochlorous acid is an extremely potent germicide at pH levels between 6.5 and 7.5, which covers most wastewater applications. However, it is also a highly active oxidizing agent and is therefore short-lived as it reacts with ammonia to form chloramines as: NH3+ HOCI —> NH.C1 (monochloramine) + H2 0 NH 2C1 + HOCI —> NHC, (dichloramine) + H20 NHCI 2+ HOCI —> NC13 (nitrogen trichloride) + H20 These reactions are extremely important, as the disinfecting power of a unit of chlorine as hypo- chlorous acid is between 25 to 100 times as great as that of a unit of chlorine as monochloramine. If the effluent has not gone through a quality nitrification/denitrification process, the levels of ammonia at the chlorine contact stage will be high enough to convert the potent chlorine to a less- than-potent monochloramine. In addition to combining with ammonia, hypochlorous acid reacts with amino acids, proteins, and other organic matter to produce chlorine compounds which have very low disinfecting power, and it combines with sulfites, nitrates, and ferrous or manganous ions to produce chlorine compounds 7