Treatment of waste liq. rich in ammonia - by neutralisation with strong acid and concentrating under reduced pressure to produce colourless, almost odourless slurry

摘要

In the parent patent waste liqs. rich in NH3 are brought at laeast to neutrality, pref. to pH 5.5-6.5, by addn. of strong acids. In this additive the liquids are waste water or drainage water of any kind, e.g. liq. manure, draining water from waste pumps, waste water from coking plants or chemical industry, or rinsing water from denitrification in power plants. Pref. the pH is adjusted by addn. of H2SO4, or H3PO4, and the liq. is then conc., pref. under reduced pressure, and esp. to dryness. An antifoam and an agent retarding incrustation may be added before concentrating. In an example, 3 L of a drainage water from a waste dump was brought from pH 9.25 to 6.80 by addn. of 100 ml or 20% H2SO4, and was conc. to 1/6 of the vol. The concentrate was a free-flowing crystal slurry, which was colourless, clear, and almost odourless, and could be further purified in a sewage plant. The condensate had following properties pH 9.35 vol. 2480 ml; NH3 content 0.86 g/l (12.5 g/l); salt content - (70 g/l); chemical O2 demand 0.376 g/l (24.2 g/l); nitrate content 0.124 g/l (0); where the figures in brackets are for the initial drainage water.