Pretreatment of Industrial Wastewater for ZLD/Resources Recovery An Application of Oxidative Evaporation Technology Philip Chen, PhD, P.E. O E Technology, LLC Info@oetech.com 1
Process Plant Bio-Unfit Bio-degradable Conventional Industrial Wastewater Treatment Systems Removes: Suspended Solids Dissolved COD Refractory COD Dissolved Salts Primary Sedimentation Secondary Activated Sludge Tertiary AOPs Add-On Membrane Separation Reuse Reject Pretreatment Neutralization Reduce/destroy COD 20-30% of Flow Through- Put 2
Oxidative Evaporation Process A low energy wastewater evaporator Remove contaminants (COD) in water with Oxygen as oxidizing agent Utilizing reaction heat to evaporate water- a low energy evaporator Recover water and dissolved solids into two segregated products Vapor condensate Liquid waste O-E O-E Process Process Salts in solid form O2 3
Process Plant Bio-Unfit Biodegradable Conventional Wastewater Treatment Combined With O-E Process Removes: Suspended Solids Dissolved COD Refractory COD Dissolved Salts Primary Sedimentation Secondary Activated Sludge Tertiary AOPs Add-On Membrane Separation Reuse Reject O-E Process Destroy/Reduce COD Evaporate water Segregate water & TDS Treat Reject stream 20-30% of Flow Through- Put 4
O-E Process Principles 1. Oxygen is used to oxidize organic or inorganic compounds under elevated temperature in an alkaline environment Liquid Phase Oxidation COD + O2 CO2 + H2O + ΔH Neutralization NaOH + CO2 Na2CO3 + ΔH 5
O-E Process Principles (cont.) 2. Oxidation reactions generate heat, which is utilized to evaporate water, leaving dissolved solids in solution Evaporation H2O(l) + ΔH H2O(v) 3. Liquid waste is recovered in two segregated product streams: Vapor condensate Salts in solid form 6
Reactor Flash Tank 1 Flash Tank 2 O-E Process Flow Scheme Liquid Feed Heater Crystallizer Liquid/Solid Separator Solids Mother Liquor Excess Oxygen Liquid/Gas Separator Condensate O2 Makeup 7
Illustrative Use for Treating Spent Caustic (A Total Treatment) C2H2 NaOH Make-up NaOH Solution Caustic scrubber Caustic Tank Crack gas Condensate Spent Caustic COD: 20,000-40,000 mg/l Sulfide: 10,000-20,000 mg/l NaOH: 5-10% wt Spent Caustic O-E Process Ca(OH)2 Liquid/Solid Separator CaCO3/CaSO4 Recaustilization Na2CO3 + Ca(OH)2 2NaOH + CaCO3 8
Application of O-E Process in Treating Epoxy Resin Waste To Activated Sludge Treating Epoxy Resin High Salt Effluent O-E Process COD: 10,000-30,000 ppm NaCL: 20-25% wt Water Salt Washing Suspension Set. Tank Filter To the Sea Org. Residue 9
Summary The conventional activated sludge process precludes receiving the process effluent containing biologically unfit factors. Segregating bio-unfit streams for Pretreatment is the essential measure in treating industrial wastewater A total recovery of water for re-use (i.e. ZLD) in the conventional treatment systems hinges on the water recovery from the reject of desalting operation 10
Summary (cont.) Evaporation/Crystallization technology has evolved to solve the issue of disposing of salt laden water streams, by recovering water as salt-free vapor condensate and salt in crystallized forms The O-E process is a wastewater evaporation technology; it also functions to remove COD in wastewater. It is ideal as a pretreatment measure for treating effluents high in COD and/or salts. The OE Process aids achieving ZLD in the conventional treatment systems. 11
Summary (cont.) Applications of O-E Process in treating spent caustic illustrates a Total Treatment (ZLD + Resources Recovery) The use of O-E Process as pretreatment for treating epoxy resin effluent illustrates achieving ZLD in the conventional treatment systems. 12
Conclusions 1. Evaporation allows recovery of water from contaminated effluent. In contrast, the conventional approach is to remove contaminants out of water. 2. As a result, wastewater is recovered as vapor condensate and salts in solid form, which make it possible to polish the condensate and to also recover chemicals for reuse. 3. The O-E Process is a low energy evaporator, utilizing the reaction heat to evaporate water and provides the capability of removing COD in waste water. 4. The O-E Process may find additional applications in other industries to comply with the guidelines of ZLD. 13