Separate sewerage collects waters that are being discharged from all technological lines in one of pharmaceutical factories in Bulgaria. The object of this study is slightly acidic waste water having pH=4-5 which is cleaned by neutralization. The water is neutralized in a radial settler equipped with peripheral device for collecting the waste water, where it is mixed and neutralized with Ca(OH)₂. Necessary amount of Ca(OH)₂ is added through a feeder and pump. The applied dosage is 10% higher than calculated. The mixture of Ca(OH)₂ and waste water settles in a horizontal thickener, where the sludge is removed and final settling of the overflow is conducted. After the final settling, cleaned water (overflow) is being treated together with the household waste in a town waste water treatment plant. The remained sludge has pH=8-9 and 50 to 60% moisture. The extracted sludge from the settling/radial primary and secondary settler/through pumps enters a special sludge pond where the sludge is stored. It contains organic and inorganic compounds as well as various chemical elements. The treatment of the sludge is object of the present article.