Three types of zeolite (NaP1 zeolite, analcime and chabazite) were hydrothermally synthesized by reacting fly ash with NaOH solution. The maximum conversion rate from fly ash to single zeolite is about 40%-75%, and the total conversion rate 60%-80%. The synthesis experimental results indicate that factors including vortex, viscosity, temperature, reaction time, and NaOH concentration in the reaction system strongly affect the type and conversion rate of zeolites. The batch experiments of removing Cu2+, Pb2+ and Cd2+ from wastewaters show that the adsorption capacity of zeolites synthesized is higher than that of fly ash. Keywords: coal fly ash, hydrothermal synthesis, zeolite, heavy metal, wastewater, adsorption.

Geomaterials can be cost-effective sorbents for use in water treatment. In this study, a heavily-weathered Tertiary soil from Xinzhou, China was used as a sorbent for defluoridation of high-fluoride drinking water. The soil is com-posed of quartz, feldspar, illite and goethite, with an Fe oxide content of 6.75%. Batch and column experiments were done to characterize the F-removal properties and to develop an optimal activation and regeneration procedure. The soil can be regenerated following a simple base-acid rinsing procedure. This can be performed in situ, i.e., by passing the rinsing solutions directly through the treatment column. The same regeneration procedure can be used to activate the pristine soil. Fluoride sorption is described by a Freundlich isotherm model and the bulk of the uptake occurs within 1.5h. Iron oxide coatings on soil particles and perhaps≡FeOH surface groups at particle edges of illite grains are likely responsible for the soil's F-sorption property. As collected in the field, the soil has a low permeability and is thus unsuitable for direct use in a fow-through column. Heat-treatment at 400-500℃ for 2h, however, produces a granular and permeable sorbent. Although the soil's sorption capacity (150µg/g) is about a quarter of the low end range of values reported for commercially-available activated alumina, the sorption for F-is specific. A batch sorption experiment in the presence of Cl-, SO42- and HCO3- shows little or no competition from these other anions.

A two-column reactor was designed to remove dissolved As and Cd from comtaminated water. The reactor functions by equilibrating the targered water with CO2 and directing it via saturated flow through acolumn of crushed siderite. This results in siderite dissolution and an increase in dissolved Fe(Ⅱ). The feedwater is them directed into the top of a second, aerated cloumn of crushed limestone, where it passes by unsaturated flow. The Fe2+ ion oxidizes quickly to Fe3+ and precipitates as Fe(Ⅲ) oxyhydroxide, which is an effective sorbent of AsO34-. The aeration that occurs in the second column also removes dissolved CO2 from the feedwater. This causes precipitation of Ca and Cd carbonates. Together, the processes reduce As and Cd concentrations from 1 and 3mg/1, respectively, to below detection (respectively<0.005and <0.01mg/1). A time-limited reduction in Cr conentration also occurred. Much of the As was removed in the first column of the reactor, because Fe(Ⅲ) oxyhydroxides also formed there. This was due to oxidation of Fe(Ⅱ) by Cr(Ⅵ) and other oxidants present on the input wastewater. Although As is removed in the reactor columns by a sorption mechanism, the sorbent responsible, Fe(Ⅲ) oxyhydroxide, is continuously produced during the operation of the reactor. Thus, unlike attenuation in a system with a fixed amount of sorbent, breakthrough of the As contaminant should never occur.

The response of carbonate aquifer to climate changes and ground water exploitation was studied at Shentou Springs. The springs consist of about 100 spring points. The long-term (1958-1999) annual average discharge of the springs is 6.86m3/s. The discharge has diminished since the early 1960s. In 1993, the discharge (3.81m3/s) was the smallest during the period of record. Data of restored spring discharge and precipitation during 1958-1999 were analyzed using a seasonal decomposition method. The result of analysis shows that the discharge of Shentou Springs responds remarkably to precipitation change. Lowering of ground water table and attenuation of spring discharge at Shentou in the last several decades are largely a response of the ground water system to the deficiency in regional precipitation in northern China. As compared with the effect of climate, human activities (mostly in the form of ground water abstraction) are secondary in affecting spring discharge. When the volume of exploited Quaternary ground waters that are partly recharged by karst waters exceeds 6400

The response of carbonate aquifer to climate changes and ground water exploitation was studied at Shentou Springs. The springs consist of about 100 spring points. The long-term (1958-1999) annual average discharge of the springs is 6.86m3/s. The discharge has diminished since the early 1960s. In 1993, the discharge (3.81m3/s) was the smallest during the period of record. Data of restored spring discharge and precipitation during 1958-1999 were analyzed using a seasonal decomposition method. The result of analysis shows that the discharge of Shentou Springs responds remarkably to precipitation change. Lowering of ground water table and attenuation of spring discharge at Shentou in the last several decades are largely a response of the ground water system to the deficiency in regional precipitation in northern China. As compared with the effect of climate, human activities (mostly in the form of ground water abstraction) are secondary in affecting spring discharge. When the volume of exploited Quaternary ground waters that are partly recharged by karst waters exceeds 6400