DESIGN OF A HYBRID INTEGRATED EFFLUENT' TREATMENT SYSTEM FOR PETROLEUM REFINERY

Abstract

Rapid industrialization, unplanned urban development, increasing automobile emission has resulted in serious environmental degradation. To defend and to improve environment for present and future generations by making industrial plants healthier and more pleasant to work, mitigating impact of industrialization by eco-friendly greener technologies, preserving ecological balance has become an imperative goal of mankind. Petroleum refineries are typically large sprawling industrial complex and are critical to functioning of the economy. Petroleum refineries use large quantity of water and steam in a variety of processes and approximately 3.5 — 5 m3 of wastewater from processing units are generated per ton of crude processed in a typical refinery containing oil and grease, BOD, phenols, COD, toxicity, pH, suspended solids, ammoniacal nitrogen, sulphides, TDS, cyanides, etc. In the existing wastewater treatment (WWT) system, refineries generally use trickling filters in combination with activated sludge process as a secondary treatment system. The use of sequencing batch reactors (SBR), membrane bioreactors (MBR) and reverse osmosis skids have received considerable interest during recent years to overcome the weakness of existing biological treatment system. As the concept of "Zero liquid discharge" has emerged in petroleum refineries so as to obtain all norms required by the regulatory boards, a hybrid integrated effluent treatment system for petroleum refinery has become need of time. The objective of present work is to design a hybrid integrated effluent treatment system to have the zero discharge with demineralized (DM) water parameters for the treated effluent. In the present work flow scheme, process description; process flow diagrams (PFD) of integrated petroleum refinery; refinery effluents and possible choices for their treatment; existing wastewater treatment system; and new hybrid integrated effluent treatment system has been presented to meet the requirement of zero discharge and compliance of regulatory parameters. Detailed design of individual units (viz. API, TPI, DAF, SBR, MBR and RO Skid) and equipments, plant lay out is presented in this dissertation report. As SBR is new to refinery wastewater, studies on the impact of temperature on various parameters [viz. SRT, AOUTR, oxygen required, overall yield, etc.] have been presented. Finally, cost estimation has also been done for setting up such a hybrid integrated effluent treatment system.