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Optimisation of RO Process Superstructure for Wastewater Treatment
Published in Mudhar Al-Obaidi, Chakib Kara-Zaitri, I. M. Mujtaba, Wastewater Treatment by Reverse Osmosis Process, 2020
Mudhar Al-Obaidi, Chakib Kara-Zaitri, I. M. Mujtaba
The production of wood pulp can be considered as the main process in the paper industry. This industry finishes the washing up of chlorinated pulp using water and filtration units. The produced wastewater contains two highly toxic chlorophenolic compounds of monochlorophenol (MCP) and trichlorophenol (TCP). El-Halwagi (1992) investigated an optimal RO network, pumps, and ERDs for waste-reduction applications based on multiple RO modules. This was used to separate MCP and TCP compounds from wastewater. The optimal network has taken into consideration all the RO system compounds and their interactions and stream distributions. Interestingly, the optimisation used the minimisation of the total annualised cost (TAC) of the RO network as the objective function. The TAC satisfies the annual operating cost and annualised investment cost. More specifically, the optimisation has considered a number of binary integer variables, which signify the use or non-use of RO, pumps, and ERD units. Several technical and environmental constraints were imposed in this study. Specifically, the environmental regulations of these chlorophenolic compounds were set as the discharged concentrations. Also, the operating conditions of each RO unit (type: Du Pont B-9 modules) were considered, which included the flow rate and concentrations of the characteristics of rejected and product streams of each nominated stage. Furthermore, the characteristics of each module with their upper and lower operating constraints were included. Figure 7.2 shows a number of unit operations in the RO superstructure representation as developed by El-Halwagi (1992). It contains two distribution boxes (DB1 and DB2), a pump-turbine box (PTB), and an ROB (RO stage box). The wastewater streams leave DB1 and enter PTB to be pressurised or depressurised and are then directed to DB2 to be delivered afterwards to ROB. The possibility of stream bypassing is considered due to blending the outlet streams of ROB with the inlet streams of wastewater. Table 7.1 shows the input data for the optimisation. The global optimal solution of the RO network for the removal of MCP and TCP is depicted in Figure 7.3, which shows three RO stages of 77 modules, two pumps, and two ERDs. The data on each stream as given in Figure 7.3 show the mass flow rate, mass fraction of MCP and TCP, and pressure. The optimisation resulted in a minimum total annualised cost of $193,420 per year, which has yielded a more efficient and environmentally friendly RO process.
Decrease of inhibitory effect of 2-chlorophenol on nitrification in sequencing batch reactors
Published in Environmental Technology, 2019
Miguel Martínez-Jardines, Emmanuel Pérez-Alfaro, R.O. González-Robles, Anne-Claire Texier, Flor Cuervo-López
Besides ammonium, phenolic compounds may be present in industrial effluents. Among them, halogenated, especially chlorinated as chlorophenols are contaminating soil and groundwater. Chlorophenols are present in wastewaters as by-product of pulp and paper, dyestuff, pharmaceutical and agrochemical industries, and they can be in surface waters in concentrations upto 43.8 g/L [7]. 2-Chlorophenol (2-CP) is a monochlorophenol that can be present in water because of its widespread use as a structural part of pesticides and preservatives in the wood industry [8]. Although its use for this purpose is currently banned in most of the world, in many producing countries, the pollution problems by 2-CP persist because of its long half-life in the environment [9]. Likewise, 2-CP could eventually be present in soil and wastewaters because of incomplete degradation of different chlorophenols [10] such as pentachlorophenol [11].
Removal of Phenol and Monochlorophenols Pollution from Aqueous Solutions with HDTMA-Modified Halloysite
Published in Solvent Extraction and Ion Exchange, 2021
Krystyna Kurdziel, Marta Raczyńska-Żak, Anna Kolbus
In the solutions, the appropriate pH was maintained to keep the phenol and monochlorophenol tested in the form of undissociated molecules. In phenol solutions the pH was maintained at 6.8, and in monochlorophenols solutions; 4.8, 5.6, 5.8 for 2-chlorophenol, 3-chlorophenol, 4-chlorophenol, respectively. The pKa values at room temperature are 9.99 for phenol, 8.49 for 2-chlorophenol, 8.85 for 3-chlorophenol, and 9.18 for 4-chlorophenol.[24]