Reducing loading of waste water esp. from cellulose@ industry - by physico-chemical flocculation before biological purificn.

摘要

In reducing the loading of waste waters, esp. from the cellulose industry, a physico-chemical flocculation is carried out before the biological purification, by (a) adjusting the pH of the mixed water from bleaching waste water and cellulose wash water to at least 11.2, (b) causing pptn. of the lignin component by addn. of vapour condensate and an electrolyte, (c) concentrating the resulting slurry with a polyelectrolyte and thickening with the bio-sludge from the later biological purification, and (d) bringing the pH of the treated waste water to 6.5-7.5 with part of the vapour condensate and another acid medium, and feeding to the usual aerobic/anaerobic biological waste water purification plant. The pH is pref. adjusted by addn. of a base, esp. NaOH. An ionic electrolysis is pref. used. An anionic polyelectrolyte is pref. used. ADVANTAGE - Lignin cpds. difficult or impossible to degrade biologically are removed, without raising inorganic component in the pptd. slurry. There is a 40% redn. in the chemical O2 demand, an 80% redn. in colour, and a 50% redn. in organo-Cl cpds. The treated waste water can be reused.