Response surface-optimized Fenton’s pre-treatment for chemical precipitation of struvite and recycling of water through downstream nanofiltration

Experimental investigations were carried out on a new membrane-integrated hybrid treatment scheme for removal of hazardous cyanide and phenol from coke wastewater and chemical precipitation of ammonia as a value-added struvite by-product. Fenton’s pre-treatment with response surface optimization ensured very effective removal of cyanide and phenol facilitating subsequent chemical precipitation of over 98% ammonia as pure struvite fertilizer. Integration of micro and nano-membrane filtration with these chemical treatment units raised water quality to reusable level. Largely fouling-free flat sheet cross flow membrane modules could remove over 96–98% of the chemical contaminants while still yielding a high flux of 116 l/h/sq m of the membrane surface at a transmembrane pressure of only 15–16 bars. The new integrated scheme embracing the concept of zero emission and value addition is a novel approach in continuous treatment of industrial wastewater for recycling.

► Optimization of Fenton’s process done by response surface methodology (RSM).
► 98% recovery of ammonia as struvite fertilizer achieved in chemical precipitation.
► Integration of flat sheet cross flow membrane modules turned water reusable.
► Novel approach produced struvite free from cyanide and phenol contamination.