Coproduced water

NAPL recovery can produce a significant quantity of coproduced water, especially if the system employs water table depression for collection of LNAPL. Discharge of water is a necessary part of the system. The general options available for disposal for recovered groundwater are ... 

Where the system is located at an industrial facility with its own treatment plant or where large quantities of water are produced, complete on-site treatment is often the most economical procedure. Phase separation followed by air stripping and contact biological (or activated sludge) treatments are common procedures. A more in-depth treatment of coproduced water handling is presented in Chapter 8. 

Effectiveness of most recovery operations is limited not by available technology, but rather by the inability to handle coproduced water. ... 

The primary concern with coproduced water during NAPL recovery operations will normally be removal of the dissolved fractions of hydrocarbons. As previously indicated, there are many treatment technologies available for the removal of dissolved hydrocarbons. The commonly used processes are discussed in the following sections. 

Typically at NAPL recovery sites (i.e., refineries and bulk terminals), some quantity of groundwater is coproduced. A major concern arises from this process in that the coproduced water must be treated, disposed of, or both. An evaluation process then follows on how to handle the coproduced water. A number of factors that control the ultimate fate of the water include the average volume produced on a regular basis, the level of contamination, and site-specific physical constraints. 

It is one thing to design, test, and maintain a recovery system that effectively recovers NAPL, but the handling of the coproduced groundwater is another matter. The effectiveness of a recovery system can suffer if the disposal capacity is insufficient or treatment costs are high. Additionally, a cost-effective, low operation and maintenance recovery system can quickly be turned into a high-cost system if the coproduced water fate is not coordinated with the recovery system. A key factor will be the level of treatment required, if any, prior to disposal. Three alternatives are explored surface discharge refinery reuse and reinjection. 

In summary, when undertaking a project such as the recovery of LNAPL, treatment of the coproduced water, prior to reinjection, may not be beneficial or technically necessary. A large percentage of the spilled or leaked petroleum hydrocarbon (40 to 60%) will be retained in the unsaturated zone as residual saturation. This residual hydrocarbon cannot be recovered by conventional withdrawal techniques. Without removing this continual source of contamination to the groundwater system, dissolved contamination will continue. Therefore, in most cases, it may be pointless and extremely costly to treat the coproduced groundwater prior to reinjection while the free- and residual-phase hydrocarbon contamination exists. 

The overall efficiency and effectiveness of LNAPL hydrocarbon recovery programs have also been impacted by other factors. These factors include limitations associated with LNAPL recovery from low-yielding formations, inability to gain access to optimal recovery and off-site locations, coproduced water-handling constraints, and economic constraints. 

Two of the larger LNAPL hydrocarbon occurrences, site No. 1 and 4 (see Ligure 12.23), formerly reinjected coproduced groundwater into generally the same hydros-tratigraphic zone from which it is withdrawn site No. 1 reinjected without treatment into the Gage aquifer, whereas site No. 4 reinjected into the Old Dune Sand aquifer. Because of the presence of dissolved hydrocarbons, notably benzene, in the coproduced water that is typically returned to the aquifer during LNAPL recovery operations, immediate application of the EPA toxicity characteristic rule may result in classification of the reinjected water as disposal of a hazardous waste. This, in turn, would terminate use of UIC Class V wells (which many of these operations currently... 

Oil Shale and Solvent-Refined Coal Liquids. Measurable amounts of the heavy elements Co, Hg, As, Zn, and Se were present in both crude shale oil and in the coproduced water from the Livermore Retort Run S-11 and the Laramie 150 T Retort Run 13. In addition, the process waters from both retorts contained significant Br (bromine) and Sb, and the water from the Laramie retort contained significant uranium (U). The data for the oil and water are presented in Tables V and VI. Independent data for several elements in the Livermore S-11 oil, water shale, and split shale can be found in Reference 10. The results for process solvent and light oil from the solvent-refined coal plant are shown in Table VII. These two liquids were generally low in trace elements, although the process solvent contained some Zn and the light oil contained measurable amounts of Zn, Br, Cr, and As. Estimated precisions for the elements shown in Tables V, VI, and VII are given in Table VIII. Independent data for a number of elements in solvent-refined coal materials can be found in Reference 11. 

Both at 70 and 80 °C, selectivity starts to decrease above 60% conversion, but more rapidly at 80 °C (product yield at 95% conversion <60% at 80 C >75% yield at 70 °C). Selectivity loss at higher conversions can be explained by competing addition of coproduced water instead of methanol to the 3-methoxyacrylate intermediate. In contrast to the stable 3,3-dimethoxy methyl propionate acetal product formed by methanol addition, the hemiacetal 3-methoxy-3-hydroxy methyl propionate generated by addition of water is prone to overoxidation, especially at higher reaction temperatures. Consequently, 3,3-dimethoxy methyl propionate selectivity benefits from increasing the methanol/methyl acrylate ratio. The results of variation of methanol/methyl acrylate ratio on activity and selectivity are depicted in Chart 11.2c,d, respectively (Pd/Cu/Fe/methyl acrylate 1/500/500/25000 oxygen pressure 0.2 MPa). Whereas conversion rates are equal at different methanol/methyl acrylate ratios, 3,3-dimethoxy methyl propionate selectivity erodes to 50% above 90% conversion at a low methanol/methyl acrylate... 

S. Mondal, C. Hsiao, S. Wickramasinghe, Nanofiltration/ reverse osmosis for treatment of coproduced waters. Environmental Progress 2008, 27,173-179. 

Synergistic extraction of As and Hg from natural gas coproduced water vwHFSLM. Cyanex 471 and Aliquat 336 As 94% extraction/32% recovery Hg 100% extraction/95% recovery As and Hg level in the treated water below the legislation limits Lothongkum et al. (2011)... 

CeO -ZrOj [Ce/(Ce + Zr) = 0.2 and 0.33] binary catalysts were also investigated for DMC synthesis from methanol and CO [156]. In all of these cases, methanol conversion was lower because the coproduced water shifts the equilibrium toward the reactants side. In order to overcome these problems, water trapping agents including molecular sieves [157] and 2,2-dimethoxy propane... 

Abercrombie HJ (1991) Reservoir processes in steam-assisted recovery of bitumen, Leming pilot, Cold Lake, Alberta, Canada compositions, mixing and sources of coproduced water. Appl Geochem 6 495-508... 

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