Edward S. K. Chian

Modifications of sulfur polymer cement (SPC) stabilization and solidification (S/S) process

This paper addresses the effectiveness of using sulfur polymer cement (SPC) as a binder to stabilize/solidify lead-contaminated soils. SPC, which has been used as a construction material because of its excellent resistance to acid and salt environments and its superior water tightness as compared with Portland cement concrete, has recently emerged as a possible alternative binder to stabilize/solidify soils contaminated with hazardous, low-level radioactive and mixed wastes. However, it was found that the use of SPC alone could not satisfactorily stabilize/solidify lead-contaminated soils. Nevertheless, it was shown that additives, such as sodium sulfide or sodium sulfite, could be used to greatly enhance the ability of SPC to react chemically with lead contaminants, and physicochemically to bind these compounds. These enable us significantly to lower the leachability (e.g. from 77.8 mg Pb/l to 1.28 mg Pb/l in EPA TCLP extract) of the SPC-treated wastes to the point where they can be recycled as some form of construction material.

Stabilization and solidification of lead in contaminated soils

Lead has been identified as one of the greatest threats to human health and is one of the common contaminants in many hazardous wastes. In this study, a surplus (waste) material, i.e., sulfur, was employed as a binder to stabilize/solidify lead contaminated soils. Soil samples were collected from a battery recovery plant, which had high levels of inorganic lead contaminant. Results obtained from the study indicated that sulfur binders can be used to stabilize/solidify inorganic lead contaminated soil which may or may not contain organic compounds. However, control samples, which used portland cement to solidify the same contaminated soils, showed that portland cement was also an effective binder. The potential applications of these solidified matrixes are also discussed. Due to the excellent physical, engineering and chemical leaching characteristics, sulfur solidified wastes could be used as construction fills, such as a subbase course in road pavement construction. Under some circumstances, use of the sulfur stabilization and solidification process will be a viable choice, especially where excess sulfur, recovered from various industrial desulfurization sites, becomes a waste product which requires disposal. The excess (waste) sulfur can be used as a stabilization agent for treating lead contaminated soil locally. Thus the two waste materials can be combined and converted into an environmentally stable material for recycling without having to be deposited in a landfill site. This by itself meets the requirements for being a sustainable technology as favored by the emerging world-wide trend of the economy for the future.

Solubility of polychlorinated biphenyls and capacitor fluid in water

Abstract A quantitative method to determine the solubility of polychlorinated biphenyls (PCBs) and used capacitor fluid in water was developed employing high-resolution glass capillary-column gas chromatography. The responses of the electron capture detector to mono-, di-, tri- and tetra-chlorobiphenyls and an internal standard were used to estimate the solubility of the PCBs. Results of the rate of dissolution of Aroclor 1242 and used capacitor fluid in water indicated that a period of five months was required to reach equilibrium. The water-solubile fractions of Aroclor 1242 and used capacitor fluid (Aroclor 1242-impregnated) were found to be identical. Certain isomers of the mono-, di- and poly-biphenyls in Aroclor 1242 were relatively soluble and were identified as 2-mono-, 2,4′-di-, 2,5.2′-tri-, 2.3,2′-tri-, 2,5.4′-tri-, 2,5.2′,5′-tetra-, 2,4.2′,5′-tetra-, 2,4.2′,4′-tetra-, 2,3.2′,5′-tetra- and 2,4.3′,4′-tetra-chlorobiphenyl. In general, the water-soluble fractions of the PCB mixtures were richer in the lower chlorinated isomers than the original PCB mixtures. The solubilities of Aroclor 1016, 1221, 1242, and 1254 were 906. 3516, 703 and ∼70μg1 −1 , respectively, whereas the solubility of the used capacitor fluid was the same as that of Aroclor 1242.

Adsorption of water‐soluble polychlorinated biphenyl aroclor 1242 and used capacitor fluid by soil materials and coal chars

Abstract Adsorption of the water‐soluble PCBs Aroclor 1242 and a used capacitor fluid (impregnated with Aroclor 1242) by five earth materials and their low‐temperature ashes were studied under constant‐temperature laboratory conditions. The five earth materials studied were medium‐temperature coal char (MTC), high‐temperature coal char (HTC), Catlin soil (CS), montmorillonite clay (MC), and Ottawa silica sand (OS). Adsorption followed the series MTC > HTC > CS > MC > OS. There were no significant differences between adsorption of the Aroclor 1242 and the used capacitor fluid by any of the five earth materials. A simple linear relation described the adsorption of PCBs from aqueous solution by the earth materials and yielded an adsorption constant (K) unique to each adsorbent. Very highly significant (.001 level) linear correlations were found for K as a function of total organic carbon (TOC.), the coefficient of determination, r 2 equals 0.87; K as a function of the surface area measured with carbon dioxid...

Characterization of Major and Minor Organic Pollutants in Wastewaters from Coal Gasification Processes

Abstract In order to investigate the feasibility of anaerobic biological treatment for wastewaters generated from thermal gasification processes of coal, a characterization program was implemented whose major effort consisted in the elucidation of specific organic constituents contained in the wastewater. Solvent extraction in acid and base conditions followed by glass capillary gas chromatography in combination with several detectors (i.e., FID, NPD, and MS-DS) were employed for the investigation of major and minor “extractable” organic constituents. Direct aqueous injection on a polar glass capillary column (i.e., OV-351) was used for the major “nonsolvent extractable” organic constituents amenable to GC. The identity of 28 organic compounds was confirmed by comparison with pure standards. Phenol, the three cresol isomers, 5,5-dimethyl-hydantoin and 5-methyl,5-ethylhydantoin were identified as major wastewater constituents. Several substituted phenols (e.g., methyl, dimethyl, trimethyl, methylethyl, hyd...

Investigation of a comprehensive approach for trace analysis of dissolved organic substances in water

Abstract An isolation—fractionation scheme for the analysis of dissolved trace organic substances in natural and drinking waters was developed. The principle behind this scheme was to concentrate dissolved organic solutes and separate them into fractions by adsorption on different adsorbents (XAD-8 resin, AG-MP-50 cation-exchange resin and Carbopack B graphitized carbon black) under varying pH conditions. Test solutions containing 22 model organic substances and inorganic salts were used to monitor process performance. High-resolution gas chromatography was employed for the separation and quantitation of each model compound. Chemical derivatization procedures were established for several highly polar model compounds. Gas chromatography—mass spectrometry was used for the confirmation of compound identity in each separated fraction.

A model study of ozone-sparged vessels for the removal of organics from water

Abstract Ozone-sparged vessels for the oxidation of a model organic compound, methanol, was studied. The parameters under study included superficial gas velocity, the gas phase ozone concentration, the rate of ozonation of methanol and its oxidative products, the residence time, etc. The scale-up method based on the mathematical model developed in this study accurately predicts the superficial gas velocity and the gas phase ozone concentration required for two larger geometrically similar vessels to achieve the same level of total organic carbon removal obtained in a small vessel.

Desalination of Seawater by Reverse Osmosis

Desalination allows the use of non-conventional water sources such as seawater for the production of potable water. Reverse osmosis (RO), one of the technologies for desalination, is becoming popular in the water industry. In this chapter, theory of RO process, plant configurations, and practical considerations related to the plant operation are addressed. Factors such as high permeate flux, high solute rejection, and mechanical and chemical stability govern the production of membranes for RO. Cellulose acetate membrane is popular due to the chlorine and fouling resistance. When it comes to rejection, thin film membranes are advantageous. Membranes are usually arranged in modules. Concentration polarization and compaction are two major limiting factors in the RO technology. Feed water must be pretreated using conventional and/or membrane filtration technologies in order to minimize membrane fouling. Reduction in permeate, pressure drop over the system, and decrease in rejection are the indications for the requirement of cleaning and regeneration of membranes. Chemical and/or physical methods can be used for the cleaning and regeneration of membranes. A case study and the recent developments are discussed in order to enhance the understanding of the process.

Reverse Osmosis Technology for Desalination

Desalination technologies are intended for the removal of dissolved salts that cannot be removed by conventional treatment processes. Thermal distillation technologies have been used in some ships for more than 100 yr. Desalination was used on a limited scale for municipal water treatment in the late 1960s. The past four decades can be divided into three phases of development: (1) 1950s was the time for discovery; (2) 1960s was concerned with research; and (3) 1970s and 1980s has been the time for commercialization. In the beginning of the 1970s, the industry began to concentrate on commercially viable desalination applications and processes.

Behavior of radionuclides in sanitary landfills.

his study was undertaken to evaluate the possibility of disposing low-level radioactive waste in sanitary landfills with leachate containment to prevent environmental releases. To meet this objective, two simulated landfills, each 200 l. in volume and containing 55 kg of municipal refuse, were operated in the laboratory with simulated rainfall additions for a 9-month period to observe the extent to which radio-cobalt, -cesium, -strontium and tritium were leached into the liquid phase. One of the units was operated with leachate recycle, the other as a single pass control. Liquid samples were analyzed weekly for 3H, 58Co, 85Sr and 134Cs tracers. Weekly analyses were also performed for approximately 30 parameters to define the degree of stabilization of the waste. Major parameters included BOD, COD, pH and concentrations of specific organics, metals and gases. Concentrations of stable cobalt, strontium and cesium were also measured periodically. Soluble radioactivity levels in both systems were reduced by factors of 50 for 58Co, 5 for 85Sr and 7 for 134Cs, taking radioactive decay and dilution into account. Some radionuclide removal from the liquid phase was associated with major chemical changes in the landfills that occurred within 80 days for the control system and within 130 days for the recycle unit. Observed acid, sulfide, and CO2 concentrations suggested mechanisms for removing some of the radionuclides from leachate. Detection of 3H in the off-gas indicated that less than 1% of tritiated waste became airborne. The waste in the leachate recycle unit was more completely stabilized than in the control unit.