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Specialized Unit Processes
Published in Ralph L. Stephenson, James B. Blackburn, The Industrial Wastewater Systems Handbook, 2018
Ralph L. Stephenson, James B. Blackburn
Current environmental standards have a significant impact on the spent caustic treatment system design. The disposal of spent caustic by conventional methods such as deep well injection is becoming environmentally unacceptable. Also, spent caustic can contain high concentrations of toxic constituents that make treatment in conventional biological treatment systems difficult or impossible even after neutralization and dilution.
Liquids Processing
Published in Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney, Fundamentals of Natural Gas Processing, 2019
Arthur J. Kidnay, William R. Parrish, Daniel G. McCartney
Figure 15.3 shows the process for a nonregenerative caustic wash. Many facilities with smaller amounts of organic sulfur to be removed use this process. The system shown in Figure 15.3 is often followed by a water wash to remove any entrained caustic and prevent embrittlement of downstream equipment. For larger facilities, a regenerated system is more commonly used to minimize caustic consumption and spent caustic disposal costs.
Removal of Micro-Pollutants from Wastewater through MBR Technologies: A Case Study on Spent Caustic Wastewater
Published in Zainura Zainon Noor, Noor Salehan Mohammad Sabli, Sustainable Water Treatment, 2017
Noor Sabrina Ahmad Mutamim, Zainura Zainon Noor
Figure 4.1 shows the stages of refined wastewater treatment. In general, physicochemical processes are used to treat spent caustic but these consume high operational cost and also cause hazardous environmental impact due to the use of high temperature, pressure, and chemical. The organic and inorganic substances in spent caustic are also partly oxidized in the physicochemical processes and still need further treatments. Spent caustic is commercially treated by applying wet air oxidation, liquid incineration, or disposal by using deep-well injection (Sipma et al., 2004). Treatment is commonly continued with biological treatment because this has the ability to enhance the removal of organic and inorganic pollutants. Sulfides in spent caustic treated by a bioreactor may be biologically and chemically oxidized into sulfate (Gerardi, 2006). Sulfides in spent caustic oxidize biologically and produce sulfate as a result of complete oxidation and sulfur under limited oxygen and the reactions are shown in Equations 4.1 and 4.2 below (Lohwacharin and Annachhatre, 2010; Sipma et al., 2004):HS−+2O2→SO42−+H+ΔG=−210.81kJmol−1HS−+0.5O2→So+OH−ΔG=−796.48kJmol−1
Synthesis and photocatalytic studies of TiO2-clinoptilolite on spent caustic wastewater treatment
Published in Particulate Science and Technology, 2018
Amin Ahmadpour, Ali Haghighi Asl, Narges Fallah
Existing environmental policies have a great effect on the spent caustic treatment system design. Typical disposal methods of dumping in a deep well or the ocean are becoming environmentally undesirable. Also, spent caustic contains high concentrations of toxic ingredients such as hydrogen sulfide and phenols that barricade the usual biological treatment even after neutralization and dilution. Spent caustic can be treated by neutralization via acid, followed by stripping by means of steam. After neutralization, stripping removes mercaptans and residual hydrogen sulfide. Residual sulfides and mercaptans in the treated caustic result in odors that may be noticeable even when diluted with wastes from other plant parts. The liquid effluent has high biological oxygen demand (BOD) and chemical oxygen demand (COD) concentrations because the major portion of the organic constituents is unaffected by the stripping process. Thus, other methods like photocatalytic degradation can be used for the COD removal of effluent that contains spent caustic due to its advantages against the naturalizing-striping method (Sheu and Weng 2001).
Investigation of transient forms of sulfur during biological treatment of spent caustic
Published in Environmental Technology, 2018
Hamed Kalantari, Mohsen Nosrati, Seyed Abbas Shojaosadati, Mahmoud Shavandi
Spent caustic (SC) is a hazardous wastewater that is produced from olefin and gas refinery plants. The Sulfidic spent caustic (SSC) produced from olefin plants contains a high concentration of sulfide, alkalinity and certain non-biodegradable organics, including benzene, phenols and other compounds [1–3]. These types of wastewater have high pH and high sodium concentration [4–6]. These wastewaters pose a serious challenge to treatment before discharge due to their chemical complexity [7]. Environmental protection organizations have imposed strict rules on the design of advanced wastewater treatment systems [8]. Conventional disposal methods such as dumping in a deep well or the ocean are not environmentally acceptable. In some cases, SSCs are sent out of the site and are reused in industries such as pulp and paper mills [1]. SC can be treated via wet air oxidation (WAO), incineration and Fenton’s oxidation. However, these methods are relatively expensive and produce secondary pollutants [9]. For instance, WAO is a common approach for treatment of SC solutions. In this process, various compounds are partially or completely oxidized at high temperatures and pressures using air-oxygen as the oxidizing agent and water steam as catalyst [10–13]. Fenton’s oxidation (treatment with H2O2) most often leads to an incomplete oxidation of the sulfide to thiosulfate resulting in a residual chemical oxygen demand of the treated SSC. In addition, the storage and handling of large amounts of hydrogen peroxide is very hazardous to safety [12].
Removing sulfide from spent caustic petrochemical wastewater with electro-Fenton treatment
Published in Journal of Applied Water Engineering and Research, 2021
Pegah Fatehbasharzad, Samira Aliasghari, Alireza Bazargan, Saman Moftakhari Anasori Movahed
Sulfur compounds coming from petroleum refineries pose serious concerns regarding environmental pollution (Fazli et al. 2018). For the removal of these toxic and odorous compounds, including hydrogen sulfide, a process of scrubbing with a strong alkaline such as caustic soda solution (NaOH, 5–10 wt%) is the industry standard (Hashemi et al. 2019). The waste solution resulting from the reaction between gaseous sulfur compounds and caustic soda is known as spent caustic (Alipour and Azari 2020). The US Resource Conservation and Recovery Act (RCRA) has designated spent caustic as a D003 (reactive sulfide) hazardous waste (Nuñez et al. 2009).