Advanced Process Engineering And Comissioning Of Wastewater From Refineries

With the continuous development of the society and the living standard of people, the demand of water also increases accordingly. Water scarcity and water pollution constrain the construction and development of the economy. Sewage recycling is one of the important methods to release water shortage. Water consumption in refineries is large (their effluent is large too), of which more than 90%is consumed for cooling equipments. Taking a refinery with 5mt/a processing capacity for example, the makeup in circulating cooling water system will be 3600m3 per day. Therefore, it is with great ecological and economic potential to use recycling water as circulating cooling water.There are mainly two kinds of sewage in a refinery in Hebei, wastewater with minerals and oily wastewater. These two kinds of wastewater were disposed to meet the criteria demanded by " Integrated Wastewater Discharge Standard GB 8978-1996" (Class Jl) and "Chlorine Emission Standards of HeBei" (DB13/831-2006, Class Ⅲ). In order to reduce water consumption and increase the efficiency of sewage recycling, the refinery applied an advanced treatment process on oily wastewater, after which the disposed water is used as circulating cooling water and irrigation water.By analysis of the quality of oily wastewater and comparison among various technical schemes, a new combined process "internal recycling biological aerated filter & Ⅲ) clarification tank & shifting sand filtration" is used successfully in the advanced disposal and water recycling project in the refinery. The process design and operation test of this project were totally done under the guidance of GB standard.The practice shows that, by advanced disposals, the removal rate of COD, Oil, SS, NH3-N and total hardness can reach 52%,87%,84%,91% and 46% respectively. The operation status of the project is stable and the effluent meets the demand of "Assessment Standards for Water Consumption and Recycling for Refineries" (QSH0104-2007).The design capacity of the project is 10800m3/d with a total investment of 15.0869 million yuan. The treatment cost of wastewater is 0.83 yuan/m3. Thanks to the new project, the recycling rate of wastewater is increased from 20% to 70%, thus the emission is reduced dramatically, which in turn contributes to the protection of groundwater and environment surrounded. The successful application of the project produces greater benefits for the society and the environment, as well as the economy.