Effect of Fe2+ and Fe0 Applied Photo‐Fenton Processes on Sludge Disintegration

The disintegration of waste active sludge was investigated by photo‐Fenton processes. A batch study was conducted to evaluate parameters, such as Fe²⁺ and Fe⁰ ions and H₂O₂, governing the activated sludge integration by the photo‐Fenton process. Under optimum conditions, the concentration of soluble chemical oxygen demand (SCOD) with the classical Fenton process (CFP) increased very rapidly in the first five minutes due to the sufficient presence of reaction components in the medium, and then the rate of increase declined. In the modified Fenton process (FTP), the SCOD concentration increased more slowly as metallic iron powder must first be dissolved. The photo‐Fenton process proved to be a feasible and efficient process for the disintegration of waste sludge.     

炼油生化剩余污泥催化深度减量技术的工业应用

大幅减少炼油生化剩余污泥对降低企业污泥处理和处置费用、保护生态环境意义重大。考察了炼油生化剩余污泥催化深度减量SMR技术工业化的处理效果，运行结果表明：对含水率98.3%的炼油生化剩余污泥，经过SMR污泥减量装置的处理，污泥脱水性能得到显著改善，脱水残渣平均含水率57.1%、污泥量减少99.4%、挥发性悬浮物平均去除率78.3%、消解液BOD₅/COD比为0.31，达到了污泥深度减量化的目的。     

大冶有色金属公司铜冶炼污泥综合利用

研究采用浸出-沉淀-(载体)浮选法和硫酸、硫脲浸出法回收大冶有色金属公司铜冶炼污泥中铜、金、银,并以污泥浮选尾矿及浸出渣与诺砂、粉煤灰等固体废弃物作为原料,制污泥压制品。铜精矿产率和品位分别为19.72%和14.25%,铜回收率89.06%,金品位和回收率分别为36.80g/t和62.61%,银品位和回收率分别为1090g/t和77.43%。污泥压制品养护过程中强度增长速度正常,达到了国家建材行业标准和危险废物鉴别标准。     

木质纤维沥青混合料性能研究

近年来,从总体性能评价和工程上应用的经济性来考虑,路用木质纤维稳定剂成为了建设SMA沥青路面首选的一种添加材料。但究竟是使用颗粒状路用木质纤维的好,还是使用松散状路用木质纤维的好,目前还没有一个明确的说法。本研究选用颗粒状路用木质纤维和松散状路用木质纤维进行路用性能试验,试验结果表明,颗粒状路用木质纤维较松散状路用木质纤维在路用性能上有明显优势。     

Mechanical sludge disintegration for the production of carbon source for biological nutrient removal

The primary driver for a successful biological nutrient removal is the availability of suitable carbon source, mainly in the form of volatile fatty acids (VFA). Several methods have been examined to increase the amount of VFAs in wastewater. This study investigates the mechanism of mechanical disintegration of thickened surplus activated sludge by a deflaker technology for the production of organic matter. This equipment was able to increase the soluble carbon in terms of VFA and soluble chemical oxygen demand (SCOD) with the maximum concentration to be around 850 and 6530 mgl(-1), for VFA and SCOD, respectively. The particle size was reduced from 65.5 to 9.3 microm after 15 min of disintegration with the simultaneous release of proteins (1550 mgl(-1)) and carbohydrates (307 mgl(-1)) indicating floc disruption and breakage. High performance size exclusion chromatography investigated the disintegrated sludge and confirmed that the deflaker was able to destroy the flocs releasing polymeric substances that are typically found outside of cells. When long disintegration times were applied (>or=10 min or >or=9000 kJkg(-1)TS of specific energy) smaller molecular size materials were released to the liquid phase, which are considered to be found inside the cells indicating cell lysis.     

The chemistry of heavy metals in digested sewage sludge—II. Heavy metal complexation with soluble organic matter

Characterisitcs of copper-binding, in the soluble fraction of a digested sewage sludge, were determined using ion-selective electrodes. Results showed that ion exchange with protons is a principal component in copper binding and that the soluble organic matter has a cation exchange capacity of 8.86 m-equiv g⁻¹ at pH 6.5. A pH-dependent exchange constant, defined in terms of mole fractions of exchange components, describes the data in the pH range 2–8 and is independent of both pH and the extent of exchange in the range 5.5–8. Supplementary data include acid/base titration curves and simple kinetic measurements. Anion uptake is insignificant in the pH range 2.5–7. A model of the aqueous phase of a sewage sludge, containing soluble organic matter with only copper and protons as competing ions, predicts that at pH 7 over 99% of the copper present will be bound to the soluble organic matter.     

Activated sludge deflocculation under temperature upshifts from 30 to 45 degrees C

Twelve independent batch experiments (<9h) with fresh municipal activated sludge were conducted to assess the occurrence and the mechanisms of deflocculation under a temperature shift from 30 to 45 degrees C. In each experiment, a transient reactor (2 L) was subjected to the temperature shift and a control reactor was operated at a constant temperature of 30 degrees C. The occurrence of deflocculation was demonstrated by the increase in turbidity and in the concentrations of biopolymers in the sludge supernatant from the transient reactor. The maximum levels of proteins in the supernatants ranged from 53 to 81 mg/L, for DNA from 34 to 36 mg/L, for humic compounds from 20 to 40 mg/L, and for carbohydrates from 21 to 31 mg/L. All the biopolymer concentrations in the control reactor remained below 5-10 mg/L. The release of biopolymers was accompanied by an increase in sludge supernatant conductivity (16-32% increase, up to 1.20 mS/cm), soluble chemical oxygen demand (from 129 to 440 mg/L), total suspended solids (>25 mg/L up to 128 mg/L), and a decrease in the mixed liquor volatile suspended solids (up to 11%). The temperature shift was also found to inhibit microbial metabolism by reducing the sludge biomass substrate removal capacity, as measured by oxygen-uptake rates. The temperature shift had a marginal effect causing sludge lysis (as an increase in beta-galactosidase activity) and had no significant impact on sludge viability (live/dead ratio of bacterial cells). It was concluded that sludge deflocculation under a temperature shift from 30 to 45 degrees C involves the solubilisation of extracellular polymeric substances from the flocs and likely also floc fragmentation. In addition, sludge deflocculation and the inhibition of microbial metabolism explain the poor treatment performance observed in previous continuous reactors under similar temperature shifts.     

Characteristics of sludge developed under different loading conditions during UASB reactor start-up and granulation

Sludge characteristics available inside the reactor are of vital importance to maximize advantages of UASB reactor. The organic loading rate and sludge loading rate applied during start-up are among the important parameters to govern the sludge characteristics. Effects of these loading rates on the characteristics of the sludge developed are evaluated in six laboratory scale UASB reactors. The sludge characteristics considered are VSS/SS ratio of the sludge, sludge volume index, specific gravity, settling velocity and metal contents of the sludge developed under different loading rates. The experimental results indicate that, for developing good characteristics sludge, during primary start-up from flocculent inoculum sludge, organic loading rate and sludge loading rate should be in the range of 2.0-4.5 kg COD/m3 d and 0.1-0.25 kg COD/kg VSS d, respectively (chemical oxygen demand, COD). Proper sludge granulation and higher COD removal efficiency will be achieved by these loading rates.     

Environmental aspects of the use of NTA as a detergent builder

The behaviour, fate and significance of the detergent builder nitrilotriacetic acid (NTA) has been reviewed with particular reference to the removal of NTA during wastewater treatment and the effects of NTA on heavy metal solubility both during treatment and in the receiving environment. It is concluded that NTA removal during secondary biological treatment is subject to considerable variation, both temporal and between works as a result of changes in NTA load, temperature, water hardness and treatment process parameters. As a result of such variability, effluent NTA concentrations may be sufficient to mobilise heavy metals resulting in metal contamination of receiving waters and potable waters, particularly in areas of low effluent dilution and high water re-use. Removal of NTA during primary sedimentation and septic tank treatment is concluded to be predominantly due to adsorption to the sludge solids while removal in anaerobic sludge digestion is subject to operational characteristics of the treatment works. Disposal of NTA contaminated sludge to land may contaminate groundwaters and affect heavy metal speciation, while the disposal of contaminated sludge or sewage to sea may result in toxic algal blooms, in addition to effects on metal speciation.     

Assessing wastewater metal toxicity with bacterial bioluminescence in a bench-scale wastewater treatment system

The effectiveness of a previously developed toxicity monitoring method for activated sludge wastewater treatment employing a bioluminescent bacterium (Shk1) was evaluated in batch experiments and a bench-scale activated sludge system exposed to heavy metals (Cu, Zn, Ni, and Cd). Influent wastewater (primary clarifier supernatant) and activated sludge from a municipal wastewater treatment plant were used in both batch experiments and in the bench-scale wastewater treatment system. Shk1 bioluminescence was most sensitive to Cd and Zn, followed by Cu, and then Ni in order of decreasing sensitivity. In contrast, activated sludge specific oxygen uptake rate was most sensitive to Cu, followed by Cd and Zn, and finally Ni. The same pattern of sensitivity was observed in batch and bench-scale evaluations. Batch experiments examining the effect of metal adsorption were performed. The adsorption of metals to activated sludge and reduction in bioavailability due to chelation by soluble organics or by precipitation in wastewater was found to be an important effect in mediating differences in toxicity response between bioluminescence and respirometry. Batch adsorption experiments indicated that the activated sludge adsorption capacity was highest for Cu, followed by Cd, Ni, and then Zn. A simple mathematical model for the soluble metal concentration in the aeration basin and clarifier was developed utilizing metal distribution coefficients determined from the batch adsorption experiments. Model predictions compared well with results from the bench-scale activated sludge experiments.