This investigation was to evaluate the performance of a thermodynamic model using nonlinear driving force in conjunction with the Langmuir model exemplified by the adsorption of benzene and carbon tetrachloride onto activated carbon in mono- and binary-adsorbate systems. Results show that model-fitted adsorption and desorption rate constants could well predict the adsorption isotherms and breakthrough curves under various conditions. This numerical model can provide adsorption and desorption rate constants. The kinetic parameters are of the same order of magnitude as reported in several studies. Under high reaction temperatures, both the adsorption and desorption rate constants increased while equilibrium constants decreased. A dimensionless valuable $C_0/K$ can be used to describe the relationship between adsorbate and adsorbent, and predict the service cycle during the adsorption process. For adsorption in binary mixtures, a high inlet concentration or a low temperature, the weak adsorbate, $C_6{H}_6\text{,}$ will have a high breakthrough concentration when the strong adsorbate, ${\mathrm{CCl}}_4\text{,}$ began to break through.

US EPA has proposed new categorical pretreatment standards for the wastewater generated by the Metal Products and Machinery industry, which includes all automotive plants. The oil and grease (O&G) standard (17 mg/L monthly average) is one to two orders of magnitude lower than Ford’s current discharge limits. The rationale for this low standard is to remove most organics from the wastewater. Most engine and transmission plants will not meet the standard without modification. Therefore, adsorption was studied as an add-on option to polish the effluent from the existing treatment process, either chemical de-emulsification or ultrafiltration. Five adsorbents (powdered activated carbon, anthracite, and three modified clay adsorbents) were investigated by developing adsorption isotherms for O&G and chemical oxygen demand (COD) using wastewater collected from a Ford plant. Activated carbon had the highest adsorption capacity, whereas anthracite had the lowest. For a typical O&G concentration range (0 to 30 mg/L) expected in the effluent after chemical de-emulsification or ultrafiltration, activated carbon was found to outperform all clay adsorbents studied by over an order of magnitude in terms of both adsorption capacity and costs. The removal of COD via adsorption showed a trend similar to that of O&G.

Lead–zinc tailings fall under the category of hazardous waste as per the “Hazardous Waste Management And Handling Rules” notification in India. Groundwater protection measures are to be adopted for an unlined tailings pond in which such tailings are being disposed. This paper presents the process of selection of an appropriate hydraulic barrier system for the tailings pond through field and laboratory based geotechnical investigations. Results of subsurface site investigations are presented. Two hydraulic barrier systems are compared—one in the form of an intermediate liner system (horizontal) and the other, a vertical cutoff system. The relative advantages and costs associated with both systems are evaluated. The study shows that the vertical cutoff system is more cost effective and advantageous for the tailings pond because of the presence of sound rock at shallow depth. The design of backfill material for the cutoff wall, using bentonite as an additive, is highlighted.

Prediction of the pollutant migration in complex soil systems requires an understanding of advection, dispersion, and adsorption processes. This paper focuses on the influence of the effective stress of soil on the pollutant transport processes. One-dimensional laboratory and centrifuge column tests under identical seepage conditions but with different stress distribution were conducted. One-dimensional numerical simulation of the contaminant transport model, using the computer software, POLLUTE Ver. 6, was carried out to curve fit the two column test results and to determine the transport parameters based on the best curve fitting. The transport parameters such as hydraulic conductivity, hydrodynamic dispersion, and distribution coefficient determined from the bench-scale and centrifuge columns were compared. The possible effects of soil stresses on contaminant transport were discussed. The experimental results from the bench-scale column and centrifuge column studies apparently illustrate that the stress state may have some influence on hydrodynamic dispersion and less effect on the adsorption of cadmium in saturated soils.

The design and operation of complex remediation projects can often benefit from an analysis from a systems perspective, that is one in which the various components of the system are viewed holistically, and a specific objective and associated constraints are articulated. This paper reports on such an analysis of a multiyear pump-and-treat scheme for removing light nonaqueous phase liquid from groundwater with subsequent treatment of the water for removal or destruction of the sum of benzene, toulene, ethylbenzene, and xylene concentrations, polynuclear aromatic hydrocarbon, carbon oxygen demand, particulate iron, and suspended solids prior to discharge. The treatment train consists of eight unit processes linked in series. The objective is to minimize total net present value of operating costs over the projected life of the treatment facility given constraints on permitted discharge limits, and the performance characteristics and requirements of the contaminant removal processes. Results indicate that the system is especially sensitive to flow rate, fixed costs of operation, and the projected quantity of oil to be recovered prior to disengagement, with the greatest cost penalty existing for underutilization of the treatment facility. Matching pumping rate with treatment capacity is seen to be the most important design factor in minimizing overall costs, however various options available to management to improve upon non-optimal conditions are discussed.

The suitability of an aerobic biological treatment process for the removal of polyaromatic hydrocarbon (PAH) from a creosote contaminated field soil was evaluated. Project objectives were to determine: (1) the overall loss of specific PAH; (2) losses due to volatilization; (3) the effect of possible operating temperatures and microbial acclimation; and (4) the relationship between volatile losses and solid–liquid and liquid–gas partition coefficients. The results indicated that an active aerobic biotreatment process is a suitable treatment process for these contaminated soils. Overall losses that occurred were: two-ring PAH, 99–100%; three-ring PAH, 86–100%; four-ring PAH, 41–44%; and five-ring PAH, 26–37%. There was little difference in PAH removal at 20 and 35°C. The maximum volatile PAH loss that occurred was for naphthalene and ranged from 9 to 17%. For most of the other PAH, overall volatile losses were less than 1% and commonly in the 0.1–0.9% range. There were no volatile losses for some of the four-ring PAH and for all of the five-ring PAH that were measured. Volatilization became less of a factor as microbial acclimation occurred. The study documented that, in an aerobic treatment process with an active acclimated microbial population, microbial degradation of semivolatile organic chemical will be the primary loss mechanism. Several predictive relationships were determined between PAH volatile losses and liquid–gas $\left(K_H\right)$ and solid–liquid $\left(K_{\mathrm{OW}}\text{,}{K}_{\mathrm{OC}}\right)$ PAH partition coefficients.

Pollution plays an important role in the corrosion of metals. This work deals essentially with atmospheric corrosion at Oman to assess the degrading effects of air pollutions on various metals that are mostly used in the engineering systems. It is the first exposure corrosion study carried out at Oman concerning the influence of air pollution on atmospheric corrosion of metals. Common materials like aluminum, brass, copper, epoxy, galvanized iron, mild steel, and stainless steel were used for the investigation. The sites of exposure were chosen at five locations where the metals are likely to be used. Statistical analysis was carried out and a number of statistical models for the sites were developed. The statistical analysis of the test data indicated that the correlations are statistically significant at less than the 1% level. These models revealed that the weight-loss values are more highly correlated with mean nitrate and sulphate concentrations than with corresponding mean chloride and carbonate concentrations. These findings were seen at all five sites.