纳米氧化物对水泥基料化学收缩的影响

采用ASTM化学收缩试验方法,研究纳米SiO2、MgO、Al 2 O 3对水泥基材料化学收缩变化的影响,明确纳米材料种类的差异性.结果表明,各实验组水泥基材料化学收缩均经历三阶段:急速变化区、缓慢变化区、平稳区,7 d始水泥基材料化学收缩基本稳定.几种纳米材料的最佳掺量对水泥基材料的化学收缩改善作用大小为:SiO 2>...     

Effect of organic materials on the solidification of heavy metal sludge

Solidification studies were conducted using three binders, viz., Portland cement (CEM), cement-fly ash (CFA) and lime-fly ash (LFA) to solidify a synthetic heavy metal sludge containing nitrates of Cr, Ni, Cd and Hg. The sludge to binder (CEM, CFA, LFA) ratio was kept at 3.33, 1.43 and 1.25, respectively; and the effect of additive interfering organic substances like grease, oil, hexachlorobenzene (HCB), trichloroehtylene (TCE) and phenol was observed. The molded samples were cured at room temperature for 28 days and the solidified samples with and without interference were examined for the change in their physical and containment properties like bulk density and compressive strength at definite time intervals during the process of curing. The results of the analysis indicated that phenol, grease and oil had a significant detrimental effect on the compressive strength of the solidified samples during the process of curing. In contrast, the effect of HCB and TCE was less marked on the compressive strength of the sample. The observations confirm the need for the waste to binder specific studies prior to the selection of a solidification process for the treatment of hazardous waste. The results also revealed a better understanding of materials that may interfere with the immobilization of the waste constituents.     

Enhancing anaerobic digestibility and phosphorus recovery of dairy manure through microwave-based thermochemical pretreatment

Anaerobic digestion and struvite precipitation are two effective ways of treating dairy manure for recovering biogas and phosphorus. Anaerobic digestion of dairy manure is commonly limited by slow fiber degradation, while struvite precipitation is limited by the availability of orthophosphate. The aim of this work is to study the possibility of using microwave-based thermochemical pretreatment to simultaneously enhance manure anaerobic digestibility (through fiber degradation) and struvite precipitation (through phosphorus solubilization). Microwave heating combined with different chemicals (NaOH, CaO, H₂SO₄, or HCl) enhanced solubilization of manure and degradation of glucan/xylan in dairy manure. However, sulfuric acid-based pretreatment resulted in a low anaerobic digestibility, probably due to the sulfur inhibition and Maillard side reaction. The pretreatments released 20-40% soluble phosphorus and 9-14% ammonium. However, CaO-based pretreatment resulted in lower orthophosphate releases and struvite precipitation efficiency as calcium interferes with phosphate to form calcium phosphate. Collectively, microwave heating combined with NaOH or HCl led to a high anaerobic digestibility and phosphorus recovery. Using these two chemicals, the performance of microwave- and conventional-heating in thermochemical pretreatment was further compared. The microwave heating resulted in a better performance in terms of COD solubilization, glucan/xylan reduction, phosphorus solubilization and anaerobic digestibility. Lastly, temperature and heating time used in microwave treatment were optimized. The optimal values of temperature and heating time were 147 °C and 25.3 min for methane production, and 135 °C and 26 min for orthophosphate release, respectively.     

Effect of organic load on phosphorus and bacteria removal from wastewater using alkaline filter materials

The organic matter released from septic tanks can disturb the subsequent step in on-site wastewater treatment such as the innovative filters for phosphorus removal. This study investigated the effect of organic load on phosphorus (P) and bacteria removal by reactive filter materials under real-life treatment conditions. Two long-term column experiments were conducted at very short hydraulic residence times (average ∼5.5 h), using wastewater with high (mean ∼120 mg L⁻¹) and low (mean ∼20 mg L⁻¹) BOD₇ values. Two alkaline filter materials, the calcium-silicate material Polonite and blast furnace slag (BFS), were tested for the removal capacity of total P, total organic carbon (TOC) and Enterococci. Both experiments showed that Polonite removed P significantly (p < 0.01) better than BFS. An increase in P removal efficiency of 29.3% was observed for the Polonite filter at the lower concentration of BOD₇ (p < 0.05). Polonite was also better than BFS with regard to removal of TOC, but there were no significant differences between the two filter materials with regard to removal of Enterococci. The reduction in Enterococci was greater in the experiment using wastewater with high BOD₇, an effect attributable to the higher concentration of bacteria in that wastewater. Overall, the results demonstrate the importance of extensive pre-treatment of wastewater to achieve good phosphorus removal in reactive bed filters and prolonged filter life.     

Removal of organic micropollutants by coagulation and adsorption

The factors which affect removal of organic micropollutants by coagulation, sedimentation, filtration and activated carbon adsorption will be reviewed. Removal of specific compounds by coagulation, sedimentation and filtration is often slight, unless the pollutants adsorb on particles or associate with humic substances which are then coagulated. By comparison, removal of humic substances by these processes can be substantial, depending upon the water chemistry and the process conditions. Activated carbon may be applied in both the powdered (PAC) and granular (GAC) form. PAC and GAC have been used successfully throughout the world to remove odorous compounds. PAC has been used to a much smaller extent for removal of other micropollutants, but there is much potential for improvement of the application procedure so that good results can be achieved. GAC is widely used to remove micropollutants other than odor in Europe but has not been extensively used for this purpose in North America. The compounds which can be removed by GAC are presented and process monitoring procedures are discussed. Factors which limit its use include incomplete knowledge about which compounds must be removed and what effluent concentrations are acceptable.     

Electrocoagulation versus chemical coagulation: coagulation/flocculation mechanisms and resulting floc characteristics

Electrocoagulation (EC) and chemical coagulation (CC) are employed in water treatment for particle removal. Although both are used for similar purposes, they differ in their dosing method - in EC the coagulant is added by electrolytic oxidation of an appropriate anode material, while in CC dissolution of a chemical coagulant is used. These different methods in fact induce different chemical environments, which should impact coagulation/flocculation mechanisms and subsequent floc formation. Hence, the process implications when choosing which to apply should be significant. This study elucidates differences in coagulation/flocculation mechanisms in EC versus CC and their subsequent effect on floc growth kinetics and structural evolution. A buffered kaolin suspension served as a representative solution that underwent EC and CC by applying aluminum via additive dosing regime in batch mode. In EC an aluminum anode generated the active species while in CC, commercial alum was used. Aluminum equivalent doses were applied, at initial pH values of 5, 6.5 and 8, while samples were taken over pre-determined time intervals, and analyzed for pH, particle size distribution, ζ potential, and structural properties. EC generated fragile flocs, compared to CC, over a wider pH range, at a substantially higher growth rate, that were prone to restructuring and compaction. The results suggest that the flocculation mechanism governing EC in sweep floc conditions is of Diffusion Limited Cluster Aggregation (DCLA) nature, versus a Reaction Limited Cluster Aggregation (RLCA) type in CC. The implications of these differences are discussed.     

Removal of phenylamide pesticides from drinking waters—I. Effect of chemical coagulation and oxidants

Chemical coagulation with aluminium or ferric sulphates is not an effective mean for the removal of phenylamide pesticides from drinking water. The effects of chlorine, u.v.-catalyzed chlorination and chlorine dioxide on phenylamides were investigated. Several aniline derivatives and intermediate products having the amide linkage intact were detected in the treated solutions. The presence of such degradation products may exert the same undesirable effects on water quality as the parent compounds. Chlorine dioxide tends to be the oxidant of choice for the removal of phenylamides from polluted waters.     

The effect of ozonation on natural organic matter removal by alum coagulation

Natural organic matter (NOM) was extracted from a moderately colored, eutrophic surface water source (Forge Pond, Granby, MA), and fractionated into quasi-homogeneous fractions. Fulvic acid (FA) and hydrophilic neutrals (HN) were the two most abundant NOM fractions that were isolated. Adsorption affinity of the isolated NOM fractions on preformed aluminum hydroxide flocs increased with increase in specific organic charge of the fractions, except for the two most highly charged fractions, FA and hydrophilic acids (HAA), which showed less adsorption affinity than expected based on their specific organic charge. Prior ozonation of FA and HN fractions resulted in a decline and an increase, respectively, in their adsorption affinity on aluminum hydroxide surface. Prior ozonation of Forge Pond raw water resulted in a progressive decline in dissolved organic carbon (DOC) removal by alum coagulation with increase in ozone dose. It appeared that ozone applied to raw water reacted preferentially with the humic fraction of NOM, resulting in the detrimental effects of ozonation on subsequent NOM removal by alum coagulation being magnified. Forge Pond raw water was pre-coagulated to remove humic substances. Ozonation of the pre-coagulated water demonstrated the beneficial effects of ozonation on the removal of non-humic NOM through alum coagulation. A strategy for staged coagulation with intermediate ozonation was proposed for waters containing both humic and non-humic NOM for maximum DOC and specific UV absorbance at 254nm (SUVA) removal.     

Effect of long term anaerobic and intermittent anaerobic/aerobic starvation on aerobic granules

The effect of long term anaerobic and intermittent anaerobic/aerobic starvation on the structure and activity of aerobic granules was studied. Aerobic granular sludge treating abattoir wastewater and achieving high levels of nutrient removal was subjected to 4-5 week starvation under anaerobic and intermittent anaerobic/aerobic conditions. Microscopic pictures of granules at the beginning of the starvation period presented a round and compact surface morphology with a much defined external perimeter. Under both starvation conditions, the morphology changed at the end of starvation with the external border of the granules surrounded by floppy materials. The loss of granular compactness was faster and more pronounced under anaerobic/aerobic starvation conditions. The release of Ca²⁺ at the onset of anaerobic/aerobic starvation suggests a degradation of extracellular polymeric substances. The activity of ammonia oxidizing bacteria was reduced by 20 and 36% during anaerobic and intermittent anaerobic/aerobic starvation, respectively. When fresh wastewater was reintroduced, the granules recovered their initial morphology within 1 week of normal operation and the nutrient removal activity recovered fully in 3 weeks. The results show that both anaerobic and intermittent anaerobic/aerobic conditions are suitable for maintaining granule structure and activity during starvation.     

Effects of wastewater effluent organic materials on fouling in ultrafiltration

The objective was to determine the effects of wastewater effluent organic materials (EfOM) on fouling of ultrafilters (100kDa polyethersulfone (PES)). EfOM constituents were sequentially removed, first by removing particles down to the approximate ultrafilter pore size and then by removing dissolved EfOM based on functionality. Particles and colloids >20nm accounted for 19% of total organic carbon (TOC), including 96% of EfOM >100kDa. Removal of particles and colloids resulted in increased fouling, attributed to increased contact of dissolved EfOM with the membrane. Hydrophobic and hydrophilic (HPO/HPI) acids were 22% of total EfOM, and accounted for nearly all of the fouling. HPO/HPI base/neutrals were 59% of EfOM, but did not cause any significant fouling. Although HPO/HPI base/neutrals did not cause any fouling, they were the dominant EfOM constituent at the surface of fouled and then hydraulically cleaned membranes, as measured by attenuated reflectance infrared spectroscopy. Since the filtration runs were short, the effects of HPO/HPI base/neutrals on long-term fouling should be further investigated, but these results cast doubt on the presumption that organic materials that are identified during membrane autopsies are necessarily a primary cause of fouling. These results also indicate that wastewater EfOM should be treated to remove HPO/HPI acids prior to membrane filtration.     

Characterisation of the impact of coagulation and anaerobic bio-treatment on the removal of chromophores from molasses wastewater

The performance of a coagulation sequence using aluminium chlorohydrate (ACH) and a low MW polydiallyldimethylammonium chloride (polyDADMAC), and ferric chloride, for decolourising a high-strength industrial molasses wastewater was compared at bench scale. At their optimum dosages, ACH/polyDADMAC gave higher colour removal than FeCl₃ (45% cf. 28%), whereas COD reduction was similar (∼30%), indicating preferential removal of melanoidins (a major contributor to the colour) by ACH/polyDADMAC. Size exclusion chromatography and fluorescence excitation-emission matrix spectrometry suggested that chromophoric Fe-organic complexes were formed during FeCl₃ treatment of the molasses wastewater, which appeared to compromise decolourisation efficiency. Anaerobic bio-treatment of the wastewater enhanced the coagulation efficiency markedly, with FeCl₃ achieving 94% colour and 96% COD removal, while ACH/polyDADMAC gave 70% and 56% removal, respectively. The improved decolourisation was attributed to the decrease in low MW organics (<500 Da) and biopolymers by the biological treatment, leading to reduced competition with melanoidins for interaction with coagulant/flocculant. For both the wastewater and the biologically treated wastewater, ACH/polyDADMAC treatment gave flocs with markedly better settling properties compared with FeCl₃.     

Removal of organic precursors by permanganate oxidation and alum coagulation

Much is known about the removal and reaction mechanisms of the naturally occurring precursors of trihalomethanes such as humic and fulvic acids. However, another class of precursors including phenols, anilines and aliphatic diketones has not been thoroughly investigated. This study shows that these truly soluble, monomeric precursors are poorly removed by alum coagulation. The use of permanganate preceding alum coagulation provides a good reduction of chloroform in water samples containing high proportions of monomeric precursors. The process was found to be less effective for water samples containing a high proportion of humic acid. This is possibly due to the degradation products from the permanganate oxidation of humic acid. These degradation products are not readily removed by alum coagulation and become available for subsequent chloroform formation.     

Treatment of textile waste effluents by ozonation and chemical coagulation

Ozonation experiments in a multiple reactor system were conducted to investigate the efficiency of this process in reducing the color and chemical oxygen demand of the textile waste effluents. It has been observed that decolorization of those waste effluents can be achieved in less than 10 min in all tested cases. In conjunction with chemical coagulation, the chemical oxygen demand of those waste effluents can be consistently reduced by up to 70% or more. Ozonation is capable of decomposing the highly structured dye molecules into smaller ones which can be easily biodegraded in an activated sludge process. Hence combination of ozonation, chemical coagulation and the activated sludge processes can provide a very effective means for dealing with this particular type of industrial waste effluent.     

混凝方式对超滤膜出水水质的影响

采用混凝与浸没式超滤膜组合工艺处理深圳市某水库原水,对比了完全混凝-超滤工艺与在线混凝-超滤工艺出水水质的不同,考察了不同混凝方式对超滤膜出水水质的影响.结果表明,当混凝剂聚合氯化铝（PACl）的投加量为3 mg/L时,两种组合工艺对浊度的去除率均达到99％以上;完全混凝-超滤对CODMn、UV254、DOC的去除率分别为40.5％,63.1％和18.5％,而在线混凝-超滤的去除率分别为41.1％,60.4％和19.2％.在保证出水水质的前提条件下,采用在线混凝-超滤工艺可以简化工艺流程,降低工程建设和运行成本.     

中国化学建材及建筑防水材料发展展望

一 未来五年中国建设市场发展趋势 “九五”期间,建设事业各项改革进一步深化,工程建设取得新的成就,城市和村镇面貌发生了较大变化。城镇住房建设呈现持续、快速增长趋势,平均每年完成城镇住宅竣工面积达4.4亿平方米,村镇住宅建设年均完成6.5亿平方米,城乡居民住房条件有了较大改善,居住水平有了很大提高。“九五”期间,建筑业还完成城市基础设施和各类工     

有机保温材料的性能分析

对挤塑聚苯乙烯泡沫塑料(XPS)、模塑聚苯乙烯泡沫塑料(EPS)、石墨模型聚苯乙烯泡沫塑料板(SEPS)、热固型改性聚苯板、聚氨酯保温板、酚醛树脂板的主要物理性能进行了分析研究,得出了各种材料的优劣势,指出选择材料时,应扬长避短,综合利用,充分发挥各种材料的优势。     

Aerial organic chemical release from activated sludge

The objective of this study was to investigate some of the potentially controlling factors influencing the atmospheric release of volatile organic compounds from the activated-sludge sewage treatment process. A bench-scale aeration vessel was used to investigate the influence of aeration rate, suspended solids concentration and detergent concentration on the rate of stripping of hexa-chlorobicycloheptadiene (Hex-BCH) and chloroform from simulated wastewater. These compounds had previously been found to be released from an 80 mgd activated sludge wastewater treatment plant.First order kinetic decay was found for the stripping of Hex-BCH and chloroform. The influences of aeration rate, suspended solids concentration and detergent concentration on the release of Hex-BCH were each statistically significant. The increase in aeration rate appreciably enhanced the release of Hex-BCH, while increasing the concentration of suspended solids inhibited stripping. A linear relationship was found between detergent concentration and stripping rate. Aeration rate was the only significant variable influencing the release of chloroform. The results suggest that Hex-BCH is stripped from an adsorbed state and chloroform from a dissolved state.     

Effect of anaerobic reactor process configuration on useful energy production

The effect of reactor process configuration on anaerobic production of useful energy (hydrogen and methane) from a complex substrate was investigated for the following reactor systems: suspended growth, two-phase mixed, two-stage mixed, upflow anaerobic sludge blanket (UASB) reactor, and two-phase UASB. The mixed two-phase and two-stage configurations yielded the highest specific energy productions of 13.3 and 13.4 kJ/g COD fed, respectively. Reactor process configuration influenced microbial pathways in acidogenic reactors in that butyrate was the predominant volatile acid in phased configurations, whereas acetate was predominant in the staged configuration. The UASB reactor achieved the highest average daily energy production per reactor volume of 101 kJ/L reactor-d. All reactor configurations achieved high COD removals on the order of 99%. However, hydrogen represented only 3% of the total energy produced by the two-phase mixed and two-phase UASB configurations. Theoretical analysis revealed that the maximum specific energy production by the two-phase suspended-growth configuration is only 9% higher than that for a single-stage mixed reactor. Consequently, the production of hydrogen from complex substrates in these process configurations does not seem to be justifiable solely from an energy point of view. Instead, it is suggested that phased anaerobic systems should be considered primarily for improved process stability whereas resultant hydrogen production is of secondary benefit.     

Fate and effects of semivolatile organic pollutants during anaerobic digestion of sludge

Anaerobic digestion of primary and secondary sludge containing selected semivolatile organic pollutants was investigated. Typical digester operation was simulated with three, complete-mix, bench-scale digesters maintained at 35.5°C with a 30 day solids retention time. Two digesters were fed a primary and secondary sludge mixture produced from wastewater spiked with twenty semivolatile organics from the CERCLA pollutant list. The remaining digester (the control) was fed a similar mixture of sludge, but with no added organics. Operational parameters were monitored to compare the test and control units. All parameters were found to be within the limits of normal operation. Performance was near identical. An isotope dilution GC/MS method was employed for organics analysis of influent and effluent streams for all reactors. Steady-state fates of the organics were determined by mass balance. Twelve of the chemicals appear consistently and at steady state. Degradation was apparent for all components, with at least 10% of each parent compound partially or completely transformed. Sorption onto digester solids was an important removal mechanism. Results of organic analysis for the control digester highlight the effects of metabolic interferences.     

Determination of main components and anaerobic rumen digestibility of aquatic plants in vitro using near-infrared-reflectance spectroscopy

A near-infrared-reflectance (NIR) spectroscopy-based method is established to determine the main components of aquatic plants as well as their anaerobic rumen biodegradability. The developed method is more rapid and accurate compared to the conventional chemical analysis and biodegradability tests. Moisture, volatile solid, Klason lignin and ash in entire aquatic plants could be accurately predicted using this method with coefficient of determination (r²) values of 0.952, 0.916, 0.939 and 0.950, respectively. In addition, the anaerobic rumen biodegradability of aquatic plants, represented as biogas and methane yields, could also be predicted well. The algorithm of continuous wavelet transform for the NIR spectral data pretreatment is able to greatly enhance the robustness and predictive ability of the NIR spectral analysis. These results indicate that NIR spectroscopy could be used to predict the main components of aquatic plants and their anaerobic biodegradability.