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................................... <br /> The sludge solids volume is the percentage of the total sample volume that is occupied <br /> by the sludge. A well-functioning plant will have a sludge volume of thirty percent to fifty <br /> percent that has the appearance of very small particles of a sponge like mass. <br /> A low solids volume would usually indicate a newly installed plant or a previous major <br /> loss of sludge in the effluent; aeration time should be cut to the minimum amount <br /> required for proper operation. A high solids volume may indicate a high or excess <br /> solids load; this can possibly be corrected by a slight increase in aeration time or by <br /> wasting sludge to the sludge holding tank. <br /> The settling tank of a properly operating plant should appear clear to a depth of <br /> eighteen to thirty-six inches below water surface, with a blanket of sludge visible below <br /> this level; there should be little floating material on the surface. The effluent liquid <br /> should appear almost crystal clear with no murkiness, or solid particles. If there are <br /> large pieces of floating sludge on the surface and in the effluent, it is caused by either <br /> supplying too much air or by not scraping the hopper bottom of the settling tank. <br /> If the plant has fine particles of sludge floating just below the surface in the effluent, it <br /> may be slightly under-aerated or is receiving toxic material in the incoming waste. <br /> Excessive amounts of grease or cooking oil will cause this condition and may cause the <br /> sludge to become yellow in color and produce foam. If large amounts of grease collect <br /> on the surface of the settling tank, it should be removed and disposed of. Then <br /> investigate and remove the source of the grease. <br /> II. DISSOLVED OXYGEN (D.O.) TEST <br /> Another test that is a useful indicator of plant operation is the dissolved oxygen test. <br /> Testing a sample of the effluent and the aeration tank liquid with a dissolved oxygen <br /> test kit performs this test. The results are expressed as parts per million of dissolved <br /> oxygen; this is a measure of the oxygen or air available for use by the activated sludge. <br /> A normal operating plant should have dissolved oxygen content of at least 1.0 ppm in <br /> the effluent and 1 to 2 ppm in the aeration tank. <br /> M. pH TEST <br /> The pH test measures the acidity of causticity of the liquid in the aeration chamber. <br /> The pH range is from one to fourteen; a pH of one indicating completely acidic <br /> conditions and a pH of 14 indicating completely caustic conditions. The pH is <br /> measured by using a color comparator. <br /> pcsio&m-obsery&test 1-ti <br />