Paul C. Chan

Heavy metals in landfill leachate

Results based upon bench/laboratory and pilot‐scale studies reveal that both biological (aerobic and anaerobic) and physico‐chemical processes are feasible for the removal of leachate heavy metals. The aerobic process was shown to be superior to the anaerobic process. The process of adsorption was found to be superior to the ion exchange. The advantage of physico‐chemical processes over the biological process is that the former can handle excessively high concentrations of heavy metals in the influent without the detrimental effect of toxicity. Research conducted at NJIT with fly ash and clay sorbents for the removal of heavy metals from industrial sludge leachates showed these materials to be effective with the controlled flow rates and sorbent arrangements.

Mechanism and feasibility of colloidal particle removal by a microcarrier process

Pollutants associated with colloidal particles in stormwater runoff have received increasing attention. Removal of these toxic particles is of paramount importance in regulating the quality of stormwater effluents. With the promulgation of the USEPAs Enhanced Surface Water Treatment Rule, a means for the removal of these particles in an efficient and rapid manner in treatment facilities is needed. This paper reviews the mechanisms and feasibility of a high rate sedimentation process in enhancing the settling in the flocculation‐sedimentation approach. The advantages of microcarriers, namely, to enhance particle capture as well as rapid sedimentation, are presented. A series of microcarrier‐jar tests was carried out. The experimental results reveal that the microcarrier process is effective in dramatically reducing treatment time and, in turn, reducing the size of treatment facility needed in a standard coagulation/flocculation unit operation.

Environmental Geotechnical Problems in the Taiwan Strait Area

This article presents general information on environmental geotechnical problems along the Taiwan Strait Tunnel (TST) route including sea-floor characteristics. The term apparent sea-floor is introduced. This layer is due to land erosion washing down and settling in the Taiwan Strait. The depth of ocean water along the Taiwan Strait is estimated. Various soil, and rock types and marine sediments along the coastline of mainland, Taiwan Strait, and Taiwan Islands are presented. Foundation problems under adverse marine environments are discussed.

Using pneumatic fracturing for in‐situ remediation of contaminated sites

Pneumatic fracturing is an innovative technology enhancing the removal and treatment of contaminants in moderate-to-low permeability formations. The main advantages are a reduction in treatment time and the extension of available in-situ technologies to more difficult geologic conditions. Pneumatic fracturing has been successfully demonstrated in the field at a number of contaminated sites and in a variety of geologic formations. The technology is now commercially available and is being incorporated into site cleanups. This article provides an overview of the pneumatic fracturing technology, beginning with a general description of the concept and apparatus. Next, key technological considerations will be discussed including fracture initiation, fracture orientation, fracture flow, and treatable soils and contaminants. Three case studies are presented describing different applications of pneumatic fracturing. The article concludes with a discussion of cost benefits of the technology.

Synthetic Flow Generation with Stochastic Models

A first-order Markovian model was proposed based on the Three-parameter Log Normal distribution. This model was comparatively used with the Thomas-Fiering models, one formulated using Normal distribution and the other with Gamma distribution. Primary objectives of the study were: (1) to examine the satisfactory applicability of the proposed model, and (2) to investigate the importance of preserving the skewness in streamflow generation. In the methodology, each model was used to generate sequences of annual mean flows for six watersheds. Average estimates of the statistical parameters were computed for the generated sequences and then compared with the historic values. To determine the effect of skewness, the probable maximum annual flows were estimated for three return periods using generated sequences and the magnitudes due to different models were compared. The results of the study indicate the importance of preserving the skewness in flow generation. In addition, it reveals that the proposed model can be satisfactorily used.