The Effectiveness and Cost of Retrofit For Reducing Automobile Emissions

EPA has recently evaluated several automobile retrofit devices that are potentially applicable to pre-1975 vehicles. The results of this evaluation are described and used to estimate the effectiveness and cost of retrofit for reducing total automobile emissions in the period 1975-1985. It is estimated that retrofit combined with inspection/maintenance can potentially achieve reductions in automobile emissions of 33% to 60% in 1975, depending on pollutant, and 10% to 20% in 1985. The estimated present value discounted to 1972 of the average cost per retrofit vehicle is $30 to $152 over the period 1975-1985 depending on the retrofit system used. The corresponding annualized cost is $6 to $28 per vehicle.     

Inspection and Maintenance for Reducing Automobile Emissions

EPA has recently evaluated several inspection and maintenance approaches for in-use vehicles that are potentially applicable to pre-1975 automobiles. The results of this evaluation are described and used to estimate the effecliveness and cost of inspection/maintenance for reducing total automobile emissions through 1985. It is estimated that inspection/maintenance programs for pre-1975 automobiles may be capable of achieving eight and ten percent reductions in total automobile emissions of HC and CO respectively until 1980 and two to three percent reductions in 1985. The need for inspection of automobiles of model year 1975 and later, and the potential applicability of present short-duration inspection procedures to these vehicles, are also discussed.     

Statistical evaluation and analysis of safety intervention in the determination of an effective resource allocation strategy

This paper provides an analytical background for the development of an effective safety intervention program with the aim of minimizing incident rates. Safety intervention data were collected from the environmental health and safety department of an American-owned oil company in the Niger-Delta region of Nigeria. A safety model was developed to determine the safety intervention factors and interactions which minimize incident rates, with the aim of predicting a better resource allocation strategy. Five main safety intervention factors (factor A: leadership and accountability; factor B: qualification selection and pre-job; factor C: employee engagement and planning; factor D: work in progress; factor E: evaluation, measurement and verification) were highlighted and investigated to show their effects on incident rate performance. Analysis of variance test showed that four safety factors (A, C, D, and E) were significant. Statistical techniques such as response surface design plots were used to determine the resource allocation method. The developed safety model recommended the allocation of 16.66% of the available resources to the significant safety intervention activities in order to achieve the desirable incident rate. In order to reap the benefits of this research, it will be important to concentrate more efforts and resources on significant factors which have positive impacts in minimizing incident rates.     

Effect of contact time on the release of contaminants from granular waste materials during column leaching experiments

When reusing or disposing of contaminated granular waste materials there is a need to evaluate how the contaminants will interact on the pathway soil–groundwater and the effect this interaction will have on the surrounding environment. While column testing can provide a closer approximation to field percolation conditions than batch testing, there is still a need to develop column testing procedures that consider the requirements of practical testing time frames. This study evaluates the effect of different column contact times (2.5, 5, and 16 h) on the release of inorganic constituents from bottom ash and demolition waste, two commonly reused granular materials. Leaching data for representative constituents of concern, such as copper, chromium, sulfate and chloride, as well as pH and electrical conductivity was compared for all different contact times studied.Results for the materials investigated in this study showed that variations in contact time have no significant effect on the release of the selected constituents and leaching parameters at low liquid to solid ratios. However, after a liquid to solid ratio of 1 L/kg, the effect is more noticeable, and higher contact times show lower pH values as well as a reduction in the release of constituents of concern from bottom ash. In the case of demolition waste, the variation of contact time did not have a strong effect on the leaching behavior.     

The leaching characteristics of selenium from coal fly ashes

The leaching characteristics of selenium from several bituminous and subbituminous coal fly ashes under different pH conditions were investigated using batch methods. Results indicated that pH had a significant effect on selenium leaching from bituminous coal ash. The minimum selenium leaching occurred in the pH range between 3 and 4, while the maximum selenium leaching occurred at pH 12. The release of selenium from subbituminous coal ashes was very low for the entire experimental pH range, possibly due to the high content of calcium which can form hydration or precipitation products as a sink for selenium. The adsorption results for different selenium species indicated that Se(VI) was hardly adsorbable on either bituminous coal ashes or subbituminous coal ashes at any pH. However, Se(IV) was highly adsorbed by bituminous coal ashes under acidic pH conditions and was mostly removed by subbituminous coal ashes across the entire pH range. This result suggests that the majority of selenium released from the tested fly ashes was Se(IV). A speciation-based model was developed to simulate the adsorption of Se(IV) on bituminous coal fly ash, and the pH-independent adsorption constants of HSeO3* and SeO3 2* were determined. The modeling approach is useful for understanding and predicting the release process of selenium from fly ash.     

Remediation of s-triazines contaminated water in a laboratory scale apparatus using zero-valent iron powder

Atrazine, propazine and simazine were tested separately and in mixture by batch procedure in a laboratory-constructed apparatus. 3.75 l of a buffered s-triazines pesticide solution was treated at room temperature by 325-mesh zero-valent iron powder (ZVIP) (20 g/l). High performance liquid chromatography was used to separate by-products and study the decline in the pesticide’s concentrations. Results obtained show that the order of degradation was simazine, atrazine and then propazine. The half-lives (t_1/2) of the s-triazines pesticides are, respectively, 7.4, 9.0 and 10.6 min when they are treated separately, and 9.8, 11.2 and 13.7 min when they are treated together under the same conditions. The final by-product obtained after 50 min of contact of simazine with ZVIP shows a shift to longer wavelength in its UV spectrum. A similar phenomenon is shown for atrazine and propazine. Identical primary by-products are produced and subsequently degraded to 4,6-(diamino)-s-triazine, which seems to be the major by-product of the reductive treatment process. Pathways for the degradation of the studied s-triazines by ZVIP are proposed.