Membrane-integrated hybrid system for the effective treatment of ammoniacal wastewater of coke-making plant: a volume reduction approach

Nanofiltration (NF) of ammoniacal wastewater containing phenol and cyanide has been investigated for effective separation of these hazardous pollutants and for the subsequent downstream chemical treatment resulting in valuable by-product generation. Four different types of composite polyamide commercial NF membranes (Sepro, USA) were tested under different operating conditions including transmembrane pressure and recovery rate (RR). At a transmembrane pressure of 15bar, the achieved rejection of cyanide and phenol were 95% and 93%, respectively (concentrated stream) when the permeate contained 85% of ammonium-N. A high flux of 120Lm(-2)h(-1) was achieved during NF at a concentrated mode, with a volumetric cross-flow rate of 800Lh(-1) at a pH of 10.0. The RR was 60% for the NF1 membrane. Fenton's reagents (7.0 and 3.75gL(-1) H2O2 and FeSO4 center dot 7H(2)O, respectively) were used to degrade more than 99% of pollutants present in the concentrated stream. In the permeate side, 97% of was precipitated out as struvite by using Mg2+:NH4:PO4+ in 1:1:1 molar ratio at pH 9.0.