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1. Closely read the Required Reading assignment from Bahadori (2014) and the Unit Lesson within the Study Guide. 2. Open your proposal draft from Unit III and make any improvements to your draft using your professor’s feedback from the Unit III project assignment. 3. Open the Unit V Study Guide, read the unit lesson, and then work with the embedded interactive model to decide what biological and secondary treatment equipment to include in your treatment process design. 4. Continue from your Unit III Project and make your fifth level one heading titled “Biological and Secondary Treatment.” Describe the secondary treatment equipment that you engineered into your treatment process. Be sure and describe the relevance and anticipated reduction of related analytical concentrations within your industrial and hazardous waste treatment system as they correspond with each technology that you selected. You are required to describe the equipment selection in at least one page.
While we allow Bahadori (2014) to discuss sewage treatment systems within the context of the required reading for Unit V, we are going to spend a little time considering one of the ancillary aspects of sewage treatment involving hydrocarbon-laden liquid wastes. Bahadori (2014) discusses some areas of this topic in our suggested reading for this unit, but an overview of his presentation may help us better because of some often overlooked independent variables causally related to the safety of an industrial and hazardous waste treatment system. One of the critical variables related to the safety of a treatment system is the air quality surrounding the processes, particularly when hydrocarbons are present in the influent waste streams. As such, it is imperative that we understand the relationship of solubility of certain petroleum-related organic compounds and hydrocarbons in water, as well as their relative emission rates coming from the wastewater during the processes. By definition, a hydrocarbon is a compound containing only two elements, carbon and hydrogen (Hill & Feigl, 1987). While we were likely able to decant and remove much of the visible hydrocarbon and petroleum-related organic compounds from the wastewater during the physical treatment process of our system, the lighter organic compounds (specifically the light alkanes methane and ethane) may be persistent in the wastewater (Bahadori, 2014). These alkanes are sometimes called saturated hydrocarbons, due to the fact that each carbon atom is bonded with four hydrogen atoms with no double or triple bonds (Hill & Feigl, 1987). This is further complicated with the fact that these two compounds typically have very low solubility in water, and subsequently are emitted as gases in the process (Bahadori, 2014; Haas & Vamos, 1995). As such, these compounds pose threats to the safety of the process work environment, given that both methane and ethane have relatively low flashpoints. For example, methane (CH4) has a flashpoint of −368.6ºF and lower explosive limit of 5.3%, and ethane (C2H6) has a flashpoint of −202ºF and a lower explosive limit of 3.0% (Lewis, 1991). One could only imagine the threat of spark in this environment while operating the treatment process. Consequently, it is important for us as engineers to anticipate the aqueous solubility of these saturated hydrocarbons in the wastewater as a means of forecasting the emissions from the process. Bahadori (2014) presents his previous work to demonstrate calculated coefficients that can be used to correlate the mole fractions of individual components of a hydrocarbon-laden solution and subsequently reduced partial pressure of the solution. The tabulated coefficients are presented for both methane and ethane, with a follow-on formula for forecasting the hydrocarbon-water solubility of these two alkanes, as well UNIT V STUDY GUIDE Designing Liquid Waste Management Systems for Industrial and Hazardous Waste MEE 5801, Industrial and Hazardous Waste Management 2 UNIT x STUDY GUIDE Title as the rest of the continuous-chain alkane ranges of propane (C3H8) through hexane (C6H14) and hexane through decane (C10H22) (Bahadori, 2014; Hill & Feigl, 1987). Finally, the dissolved organic carbon (DOC) can then be anticipated in units of percent by weight for each petroleum-related compound and subsequently correlated as a ratio of DOC to chemical oxygen demand (COD) or DOC/COD. As such, a predicted value for DOC derived from the DOC/COD ratio (0.267) may be calculated solely from the COD measurements (Bahadori, 2014). For example, if a petroleum-laden wastewater has a COD value of 500 ppm, the anticipated calculation for predicting DOC could be made as follows (Bahadori, 2014): DOC/COD = 0.267 Where DOC = X COD = 500 ppm then X/500 ppm = 0.267 or X = 500 ppm (0.267) so X = 133.5 ppm or DOC = 133.5 ppm Still, Bahadori (2014) presents additional tabulated information derived from historical DOC concentration measurements from refinery effluents for both organics and inorganics traditionally found in those waste streams. You may find this information useful in your own engineering work for your industrial and hazardous waste treatment system currently under design in this class. Remember that the ultimate reason for predicting the DOC concentrations in the wastewater is to mitigate hazardous environmental conditions for both humans and the ecological life surrounding and interacting with the treatment process. As such, you may consider the relative intrinsic safety of pumps, motors, mixers, and other equipment that is designed into the process as part of the system. Let’s return to our interactive model and design in the biological and secondary treatment phase of our proposed industrial and hazardous waste treatment system. 1. Click here to access the interactive design model. 2. Closely review the influent laboratory report (lift station) against the effluent laboratory report (pop up report). Remember that the goal is to design our system so that the final effluent concentrations meet the established local limits for the municipal WWTP. 3. Continue to use this model in your design work for your course project (proposed industrial and hazardous waste treatment facility) again in this unit. Notice that as you design the next-to-last phase of this system, the process is noticeably dropping the concentrations of the constituents
