[Effectiveness of arsenite adsorption by ferric and alum water treatment residuals with different grain sizes].

Effectiveness of arsenite adsorption by ferric and alum water treatment residuals (FARs) with different grain sizes was studied. The results indicated that the content of active Fe and Al, the specific surface area and pore volume in FARs with different grain sizes were in the range of 523.72-1 861.72 mmol x kg(-1), 28.15-265.59 m2 x g(-1) and 0.03-0.09 cm3 x g(-1), respectively. The contents of organic matter, fulvic acid, humic acid and humin were in the range of 46.97-91.58 mg x kg(-1), 0.02-32.27 mg x kg(-1), 22.27-34.09 mg x kg(-1) and 10.76-34.22 mg x kg(-1), respectively. Results of SEM and XRD analysis further demonstrated that FARs with different grain sizes were amorphousness. Batch experiments suggested that both the pseudo-first-order and pseudo-second-order equations could well describe the kinetics adsorption processes of arsenite by FARs. Moreover, the contents of arsenite absorbed by FARs increased with the increase of arsenite concentrations. The theoretical saturated adsorption capacities calculated from Langmuir isotherm model were in the range of 6.72-21.79 mg x g(-1). Interestingly, pH showed little effect on the arsenite adsorption capability of FARs. The capability of FARs had a close relationship with their physicochemical properties. Correlation analysis showed that the active Fe and Al contents and pore volume had major effects on the arsenite adsorption capability of FARs.

[Microbial ecology analysis of the biofilm from two biological contact oxidation processes with different performance].

This study investigated the performance of one-step aerobic biological oxidation process and anoxic/aerobic two-step biological oxidation process treating modeled river water containing low carbon and rich ammonia. Biofilm microbial ecology was analyzed with multiple molecular technologies including PCR-DGGE, FISH/CLSM and FISH/FCM to investigate the succession of bacteria community and space distribution along with abundance of the main functional bacteria, and to research the micro-influential factors and the mechanism of different biological contact oxidation processes for their performance. Results showed that two-step contact oxidation process achieved higher removal percentage than that of the one-step process, with COD and NH4(+) -N removal enhanced about 10% and 32%-59%, respectively. A much thicker biofilm was obtained by the one-step process compared to the two-step process, and nitrobacterium was mainly distributed in the depth of 180-200 microm and 105-125 microm, respectively. PCR-DGGE results found that the two-step process demonstrated less microbial diversity than that of the one-step process, FISH/FCM results showed that ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) abundance increased in the two-step process with the increase of operation time, while that of the one-step process declined. Experiment results demonstrate that functional partitioning of the anoxic-aerobic two-step biological contact oxidation process could be in favor for harvesting nitrobacteria and other special bacteria in different reactor spaces, which can improve removal efficiency for organics and ammonia finally.

[Characteristics of orthophosphate adsorption on ferric-alum residuals (FARs) from drinking water treatment plant].

Batch tests have been used to investigate the characteristics of orthophosphate adsorption on ferric-alum residuals (FARs) from drinking water treatment plant. ICP, SEM and XRD analyses confirm that the FARs enriched in Fe and Al elements and presented amorphism structure. Orthophosphate sorption by the FARs can be described by the pseudo-second-order kinetics equation. Fine adsorption effects of the FARs were found under lower pH values, particularly a 40.13% drop of the adsorptive capacity from pH 4.6 to pH 7.6. The FARs with grain sizes of 0.6-0.9 mm had the highest adsorption capacity of orthophosphate. Experimental data could be better fitted by the isotherm models of Langmuir (R2 = 0.9736) and Freundlich (R2 = 0.9916). The maximal adsorptive capacity reached 45.45 mg x g(-1) estimated from Langmuir isotherm model. Compared with other natural and industrial materials, FARs has relatively higher adsorption capacity. Under similar testing conditions, it was found that only about 10% orthophosphate could be desorbed from the FARs. Further study demonstrated that the mean energy of orthophosphate sorption on the FARs was 13.36 kJ x mol(-1) and the deltaH0 > 0, deltaS0 > 0 and deltaG0 < 0, which indicated that orthophosphate sorption on the FARs was a spontaneously endothermic chemical reaction. It can be therefore highly valued that the FARs may be applied to phosphate removal from wastewater and surface water.

[Sources and transformations of nitrogen in the Fuhe River of the Baiyangdian Lake].

The sources and transformations of nitrogen in the Fuhe River were investigated by application of nitrogen isotope methods. The results showed that the values of delta15N in ammonium and nitrate were 1.35 per thousand-8.01 per thousand and -6.69 per thousand-8.36 per thousand, respectively. The industrial and municipal wastewater from the Baoding City contributed high ammonium to the river. In drying season, the processes of nitrification and denitrification were affected by both of water and sediment. In wetting season, ammonium was mainly absorbed by plants, and loss rate of nitrate was about 86.3%. The nitrate removal by denitrification reached 44.6%, whereas that by plant uptake was 55.4%, indicating the importance of vegetation in nitrogen removal. Thus, restoration of local vegetation in the river would be the key to relieve eutrophication in the lake.

[Preparation of polyaluminum silicate chloride (PASC) from tetraethylorthosilicate (TEOS) and its physicochemical characteristics].

A new type of polyaluminum silicate chloride [PASC(A)] was prepared by employing tetraethylorthosilicate (TEOS) as silicon source. By comparing PASC(A) with the conventional product [PASC(B)], the effects of B value and Si/Al molar ratio on the pH value and the Zeta potential of PASC(A) were investigated. The influence of the incorporation of silicon into PASC on the molecular structure and aluminium species was also studied by acidification method and 27Al NMR spectroscopy. The results show that the PASC(A) has higher polymerization degree, narrow distribution of molecular weight and symmetrical distribution of aluminium and silicon in PASC molecule. It is more difficult to be acidified, and moreover, it can reduce the loss of Al13 species. All the above advantages of PASC(A) are due to its special synthesis method.

Control effects of p(epsilon) and pH on the generation and stability of chlorine dioxide.

A new method, without assistance of activity ratio diagram, was applied to construct the p(epsilon)-pH diagrams for chlorine system. The optimal pH range for generation of C1O2 by contacting Cl2 (g) directly with ClO2- solution is within pH 1.35-1.94, particularly within pH 1.35-4.00 only if minimizing the formation of Cl2. It is unachievable to synthesize pure ClO2 from the reaction of Cl2 and ClO2- . Conversely, ClO2 may be present a variation of stability in different waters owing to the changed p(epsilon) and pH. ClO2 could be relatively stable if not disproportionate into ClO3-, coexisting with ClO2- (p(epsilon) 17.63 and pH > 9.68), Cl2(pH < or = 0.92) or Cl- (pH 0.92-9.68). When chlorine system has already reached the ultimate equilibria, ClO2 is a stable species in strongly acid media. As the acidity decreases, ClO2 disproportionates into ClO3- and Cl2. Aqueous ClO2 is unstable within the normal pH range. This work initially, theoretically elucidates the generation and stability of ClO2 by way of the p(epsilon)-pH diagrams.

Watershed protection and landscape enhancement by utilization of river water.

A scheme for watershed protection and landscape enhancement (WPLE) by utilization of river water was proposed to renovate water resources and protect ecological environment in Qiongshan City, Hainan Province, China. Utilization of river water may diminish the drought and flood risks. The scheme is beneficial to solve the problems of water resources shortage, groundwater declines and saltwater intrusion in the watershed. The object of the WPLE scheme is to achieve a sustainable integrated development of environment, ecology, economy and society. A kind of physically beautiful and functionally vivid landscape may exert its synthetical function on the diversity of landscape and the enjoyment of inhabitants. Feasibility of the scheme will be demonstrated by more experiments and tests, as well as observations in a long term.

Assessment of the environmental impact of artificial effluent lagoon in Jiayuguan City of China.

An artificial effluent lagoon for storing wastewater were excavated in Jiayuguan City since 1994. As a part of a demonstration project of Sino-Australia cooperation, an assessment of the environmental impact of the lagoon was carried out. The assessment was based on field and laboratory tests and predictive model. The main impacts from the lagoon site are likely to be on the groundwater system, and, to a lesser extent, on ambient air quality in the vicinity. Currently it is expected that groundwater is being polluted with effluent from the effluent lagoon. Air pollution (odor nuisance) is mainly caused by untreated effluent in the irrigation channel. The impact of high total dissolved salt (TDS) on groundwater is likely to be significant in the long run if the lagoon is continuously used. There is, consequently, no likelihood of contamination of surface water system, particularly of the city water supply system, from infiltration of effluent at the lagoon.

Culture conditions for flocculant production by Paenibacillus polymyxa BY-28.

A new flocculant-producing bacterium Paenibacillus polymyxa BY-28 was isolated from soil. The optimal culture media for flocculant production were 2% glucose, 0.3% KH2PO4, 0.1% bean cake powder, 0.05% CaC12 and 0.05% (w/v) MgSO4.7H2O. Optimal culture temperature was 30 degrees C and pH was 6-8. Flocculants produced under optimal conditions efficiently aggregated various organic and inorganic suspensions in simulated water as well as in wastewater by addition of bivalent and trivalent cations Ca2+. From Zeta-potential measurement, the dominant role of microbial flocculant in the flocculation process is based on the bridging mechanism, and the role of CaCl2 is to decrease the negative electrical charge of the Kaolin clay particles.