Preventive strategies for reuse and recycling of wastewater within the HDG production

Abstract

The hot-dip galvanizing consumes raw materials, supplies, and influence in the quantity/quality of wastewater, opening advantage for its segregation, reuse, and recycling. Therefore, the aim was to establish strategies for segregation, recycling, and preventives process of wastewater from a hot dip galvanizing enterprise (>10,000 t/year of galvanizing steel or gs). A mass balance (inputs-outputs by 1 t gs), Sindex considering organic and inorganic parameters for segregation/recycling, and Water Pinch (Zn, COD, TDS) for reuse opportunities were determined. Flow diagrams were based on three scenarios that combine segregation/reuse/recycling, comparing saving water, energy, costs, and carbon dioxide equivalent (CO2-eq) emissions. Results (mass balance) demonstrated that the water consumption in the rising phases (2,355.2 L/t gs) corresponding to 95% of the total water demand. The best scenario combined reuse, segregation and recycling, which decreased up to 36% of treated wastewater, up to 40% of chemicals consumption, about 41% of treatment cost, close to 38% of energy consumed, and up to 17% of CO2-eq emissions by wastewater treatment. Therefore, taking preventive measures without the need of technological changes (treatment) can achieve on efficient water management within of the hot-dip galvanizing production in developing countries. HIGHLIGHTS The galvanized industry consumes large amounts of raw materials, energy, and water.; Sindex for segregation/recycling and Water Pinch for reuse opportunities were used.; Rising phases correspond to 95% of the total water demand.; Segregation, reuse/recycling saved 41% in treatment costs and 90% in water use.; Water management avoided 16.5 kg CO2-eq/day due to the decrease in energy expenditure.;

Keywords

• developing countries
• environmental characterization
• hot-dip galvanizing
• sindex
• water pinch