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Nat. Env. & Poll. Tech.
Website: www.neptjournal.com
Received: 26-8-2014
Accepted: 28-9-2014
Key Words:
Oil wastewater,
Internal circulation reactor,
Two-stage biochemical
process, Biogas
ABSTRACT
In expectation to improve the properties of production wastewater with both complicated composition and high amount of organic compounds produced by oil and grease processing enterprise, pretreatment, IC anaerobic technology and the two stage biological contact oxidation technology were combined to process the oil wastewater. It was found that the removal rate of COD, oil and ammonia nitrogen could be enhanced to 99.71 %, 99.8%, 85.8%, respectively when the concentration of Influent COD, grease and ammonia nitrogen were 32500mg/L, 2800mg/L and 95 mg/L. Besides, the effluent quality could keep stable, coming up to the primary standard of the integrated wastewater discharge standard (GB8978-1996). Meanwhile, biogas, a kind of clean secondary energy, was also produced during the treatment process and could be applied in both power generation and steam production, exhibiting excellent technicality and economic.
INTRODUCTION
An oil processing enterprise, using waste vegetable oil recycling as raw materials, produces oleic acid, stearic acid, glycerol and other products. The oil wastewater comes mainly from various processes such as leaching, alkali refining, hydration, acidification, neutralization, degumming, deodorization, decolorization, filtration and washing process. Due to the intermittent discharge, the oil wastewater is of complex composition, unstable pH value, changeable water quality and quantity, and strongly harmful. The main pollution index of the oil wastewater and corresponding discharge standard are given in Table 1. The paper deals with the treatment of this wastewater by internal circulation (IC) and two-step biochemical process with generation of biogas. The economics of the process has also been discussed.
TREATMENT PROCESS
Technical Procedure
After considering the wastewater quality and related technical processes (Chen 2013, He 2001, Ouyang et al. 2013, Wang et al. 2006, Liu et al. 2011, Toru Matsui et al. 2005, Chavez et al. 2005, Zhang Z. H. 2006, Hu et al. 2004), IC and two-step biochemical process are adopted.
Wastewater is first treated by grid to remove large particles SS and then flows into the separation tank and regulation pool aiming at eliminating most of the oil slick and regulating water quality. The treated wastewater flows into the sump well and then is pumped to neutralization, coagulation and...