Rapid anaerobic degradation of toxaphene in sewage sludge

We studied the degradation of technical toxaphene in anaerobic sewage sludge from a municipal waste water treatment plant. Chlorobornanes, chlorocamphenes and related compounds were rapidly degraded, with degradation rates in the order of decachloro>nonachloro>octochloro>heptachloro approximately = hexachloro compounds. The half-lives of individual congeners ranged from <1 day to several days. We also studied the degradation of technical toxaphene in previously sterilized sludge (control), and found it was slower than in the anaerobic sludge. The chlorobornanes that degraded most rapidly in the non-sterilized anaerobic sludge were those with gem chloro substitution on the 6-member carbon-ring, including the toxic congeners, Toxicant A and B. Non-gem chloro substituted congeners, like the biologically persistent P26 and P50, also degraded, but less rapidly. Toxaphene degradation in sewage sludge proceeded primarily via reductive dechlorination, leading to HxSed, HpSed, TC2 and other persistent metabolites. Enantioselective determinations indicated little, if any, enantioselectivity in the formation and/or degradation of these compounds. The isomer and enantiomer profiles of the hexa-, hepta-, and octachlorobornanes are similar to those observed in sediment from the Baltic Sea, suggesting that technical toxaphene is the source of these compounds and that its composition was changed via similar anaerobic degradation pathways.     

Anaerobic degradation of brominated flame retardants in sewage sludge

Tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), and decabromodiphenyl ether (DecaBDE) are high production volume chemicals used as flame retardants in plastics for products such as electronic equipment, insulation panels, and textiles. The environmental safety of brominated flame retardants, especially their persistence, bioaccumulation, and toxicity is a controversial topic. Here, we studied and compared the degradation of TBBPA, HBCD, and DecaBDE under anaerobic conditions in digested sewage sludge. The half-lives of TBBPA and a technical HBCD mixture were 0.59 and 0.66 d, respectively. The fact that (+/-)-alpha-HBCD exhibited an almost doubled half-life compared to (+/-)-beta-HBCD and (+/-)-gamma-HBCD is an important finding with respect to the discussion on the persistence of individual HBCD stereoisomers and the recent reports on strong relative enrichment of alpha-HBCD in biota. We found no statistically significant enantioselective degradation of alpha-, beta-, or gamma-HBCD. Half-lives of TBBPA and a technical HBCD mixture were not dependent on the presence of additional nutrients or primers. Concentrations of TBBPA and a technical HBCD mixture decreased also in sterile control samples, however, at a rate that was more than a factor of 50 smaller than in incubations under non-sterile conditions. Compared to TBBPA and a technical HBCD mixture, DecaBDE exhibited a much longer half-life of 7 x 10(2)d in the same system. Pseudo-first-order degradation rate constants decreased according to the following sequence: TBBPA congruent with(+/-)-gamma-HBCD congruent with(+/-)-beta-HBCD>(+/-)-alpha-HBCD>DecaBDE. Preliminary investigations suggest that degradation of TBBPA, HBCD, and DecaBDE occurs in full-scale anaerobic digesters, as well.     

Plant accumulation of potentially toxic elements in sewage sludge as affected by soil organic matter level and mycorrhizal fungi.

Leek (Allium ameloprasum) was grown in pot trials in two clay loams of contrasting organic contents, with and without indigenous mycorrhizal propagules. Sewage sludges containing varying levels of Cd, Cu and Zn were added. Extractable soil metals, plant growth, major nutrient content and accumulation of metals, and soil microbial indices were investigated. The aim was to establish whether soil organic content and mycorrhizal status affected plant and microbial exposure to these metals. Extractable metals were higher and responses to inputs more pronounced in the arable, lower organic matter soil, although only Cd showed a soil difference in the CaCl2 fraction. There were no metal toxic effects on plants and some evidence to suggest that they promoted growth. Uptake of each metal was higher in the larger plants of the grassland, higher organic matter soil. Inoculation with arbuscular mycorrhizal fungi increased root Cd and Zn concentrations. With the exception of Cd (roots) and Zn (shoots), higher inputs of sludge metals did not increase plant metals. Zn and Cu, but not Cd, concentrations were higher in roots than in shoots.     

Analysis of some polyhalogenated organic pollutants in sediment and sewage sludge

A laminated sediment core collected in the southern part of the Baltic Proper was analysed for DDT compounds, polychlorinated biphenyls (PCB) including the coplanar congeners, polybrominated diphenyl ethers (PBDE) and polychlorinated naphthalenes (PCN). Two sewage sludge samples were also analysed for the same compounds.

The results of the sediment analyses indicate the presence of PCB, DDT and PBDE compounds in sediment layers dating from the 1950s and later. Neither coplanar PCB nor PCN were detected at any level of the sediment core. The PCB concentrations indicate a slight increase in levels during the last decades, while there were no changes in the levels of DDT compounds. In contrast, TeBDE levels increase 4- to 8-fold and one PeBDE congeners levels increase 10- to 20-fold. The results of sewage sludge analyses showed the concentration of the individual PBDE to be at about the same level as for the individual PCB congeners. The congener pattern in sludge samples indicates low-chlorinated products to be the main PCN source.     

Influence of the application of sewage sludge on the degradation of pesticides in the soil

A study was made of the influence of the application of sewage sludge on the degradation of pesticides in the soil. Two kinds of sludge were used, with different characteristics, one from an urban treatment plant and one from a food processing plant. Three organophosphorus insecticides, fenitrothion, diazinon and dimethoate, were studied. The relative importance was determined of the chemical and biological degradation processes, which involved experiments on soil and sterile soil samples. A comparative study was also made of the degradation of pesticide residues and the evolution of the microbial population. The application of sludge seems to have a complex effect on the degradation of pesticides, determined by the bioavailability and biodegradability of their active ingredient. The biodegradation of pesticide residues brings about alterations in the microorganism population of the soil.     

Analysis of potentially toxic metal constraints to apply sewage sludge in Portuguese agricultural soils

Environmental Science and Pollution Research - The application of sewage sludge (SS) in the soil can be a valuable way to increase its content of organic matter. However, the concentration of...     

Degradation of organic pollutants in Mediterranean forest soils amended with sewage sludge

The degradation of two groups of organic pollutants in three different Mediterranean forest soils amended with sewage sludge was studied for nine months. The sewage sludge produced by a domestic water treatment plant was applied to soils developed from limestone, marl and sandstone, showing contrasting alkalinity and texture. The compounds analysed were: linear alkylbenzene sulphonates (LAS) with a 10–13 carbon alkylic chain, and nonylphenolic compounds, including nonylphenol (NP) and nonylphenol ethoxylates with one and two ethoxy groups (NP1EO + NP2EO). These compounds were studied because they frequently exceed the limits proposed for sludge application to land in Europe. After nine months, LAS decomposition was 86–96%, and NP + NP1EO + NP2EO decomposition was 61–84%, which can be considered high. Temporal trends in LAS and NP + NP1EO + NP2EO decomposition were similar, and the concentrations of both types of compounds were highly correlated. The decomposition rates were higher in the period of 6–9 months (summer period) than in the period 0–6 months (winter + spring period) for total LAS and NP + NP1EO + NP2EO. Differences in decay rates with regard to soil type were not significant. The average values of decay rates found are similar to those observed in agricultural soils.     

干化污泥制备节能烧结墙体材料

以干化污泥作为替代燃料和造孔剂加入到以页岩为主体的原料体系中,制备出具有节能效果的多孔污泥页岩烧结墙体材料,这是提高污泥利用效率和满足村镇建筑节能建材制备的有效手段,探究了城市污泥掺量、烧结温度和烧结保温时间对烧结墙体材料试样的物理性能、力学性能的影响规律。结果表明,在采用污泥和瘠性页岩为主要原料时不能满足多孔节能烧结墙体材料挤出成型要求,而应采用压制成型工艺,当污泥掺量为15%时,烧结温度为1 050 ℃,保温时间为6 h,可以制备出性能指标优异并满足工程实用的烧结墙体材料,且污泥中的重金属可有效固溶于材料内部,气体排放也可满足国家标准中的相关指标要求,研究结果对干化污泥的利用具有较好的指导意义。     

Thermal conductivity characteristics of dewatered sewage sludge by thermal hydrolysis reaction

The purpose of this study is to quantify the thermal conductivity of sewage sludge related to reaction temperature for the optimal design of a thermal hydrolysis reactor. We continuously quantified the thermal conductivity of dewatered sludge related to the reaction temperature. As the reaction temperature increased, the dewatered sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. Therefore, the bound water in the sludge cells comes out as free water, which changes the dewatered sludge from a solid phase to slurry in a liquid phase. As a result, the thermal conductivity of the sludge was more than 2.64 times lower than that of the water at 20℃. However, above 200℃, it became 0.704 W/m?°C, which is about 4% higher than that of water. As a result, the change in physical properties due to thermal hydrolysis appears to be an important factor for heat transfer efficiency.

ImplicationsThe thermal conductivity of dewatered sludge is an important factor the optimal design of a thermal hydrolysis reactor. The dewatered sludge is thermally liquefied under high temperature and pressure by the thermal hydrolysis reaction. The liquid phase slurry has a higher thermal conductivity than pure water.     

Investigation on oxygen-controlled sewage sludge carbonization with low temperature: from thermal behavior to three-phase product properties

Environmental Science and Pollution Research - A comprehensive study was conducted on the characteristics of oxygen-controlled carbonization process of sewage sludge (SS) using thermogravimetric...     

Anaerobic formation and degradation of toxic aromatic compounds in agricultural and communal sewage deposits

Relatively high concentrations of phenol, p-cresol, phenylacetic acid and other aromatic compounds were found in agricultural and communal sewage deposits. These toxic aromatic compounds are products of the bacterial degradation of aromatic amino acids under anaerobic conditions. In laboratory experiments at 26 degrees C and under N2-atmosphere, the same aromatics were formed from the amino acid tyrosine and from gelatine in assays inoculated with sewage sludge. After exhaustion of tyrosine and gelatine, respectively, concentrations of the accumulated phenol and other aromatics remained stable for months, i.e., phenol, p-cresol, phenylacetic acid etc. are dead-end products of the bacterial metabolism under these conditions. After addition of sodium nitrate the aromatic compounds are metabolically decomposed by denitrification within weeks.     

生石灰稳定干化对生活污泥理化性质的影响

生活污泥添加其干基质量6%、12%和18%生石灰稳定干化30 d,对不同时期混合物的理化指标进行取样分析。研究结果表明,生石灰稳定干化污泥,污泥的脱水性能得到有效改善,有机质和氮素的损失率分别为14%～29%和23%～26%,磷素含量稳定;微生物检测表明添加18%的生石灰能够有效杀死蛔虫卵。     

蚯蚓过腹处理对污泥中四环素降解及大量营养元素赋存的影响

针对污泥中大量抗生素残留对环境的威胁和污泥资源化利用的瓶颈等问题,采用微宇宙实验手段研究了蚯蚓过腹处理污泥过程中四环素的降解特征和污泥蚓粪中大量营养元素的赋存特征。结果表明,污泥中的四环素降解率与处理时间呈正相关关系;室温静置32 d后,污泥中9%~11%的四环素发生降解。蚯蚓过腹处理下,污泥中四环素浓度与四环素降解率呈负相关关系,随着污泥中四环素浓度的增加,四环素降解率逐渐降低,蚯蚓过腹处理32 d后,污泥中四环素的降解率提升了45%~64%。蚯蚓过腹形成的污泥蚓粪中总氮和有机质含量显著减低,而铵态氮、硝态氮、速效磷、速效钾和总钾含量以及pH和电导率均显著升高;随着污泥中四环素浓度的增加,污泥蚓粪中总氮和氨氮含量以及pH和电导率呈显著降低趋势;污泥蚓粪中铵态氮和硝态氮含量、pH和电导率与四环素降解率均呈正相关关系。蚯蚓过腹处理能够显著提升污泥中四环素的降解率及污泥蚓粪中速效氮磷钾的含量。     

Removal of organic contaminants in bioretention medium amended with activated carbon from sewage sludge

Bioretention, also known as rain garden, allows stormwater to soak into the ground through a soil-based medium, leading to removal of particulate and dissolved pollutants and reduced peak flows. Although soil organic matter (SOM) is efficient at sorbing many pollutants, amending the bioretention medium with highly effective adsorbents has been proposed to optimize pollutant removal and extend bioretention lifetime. The aim of this research was to investigate whether soil amended with activated carbon produced from sewage sludge increases the efficiency to remove hydrophobic organic compounds frequently detected in stormwater, compared to non-amended soil. Three lab-scale columns (520 cm³) were packed with soil (bulk density 1.22 g/cm³); activated carbon (0.5% w/w) was added to two of the columns. During 28 days, synthetic stormwater—ultrapure water spiked with seven hydrophobic organic pollutants and dissolved organic matter in the form of humic acids—was passed through the column beds using upward flow (45 mm/h). Pollutant concentrations in effluent water (collected every 12 h) and polluted soils, as well as desorbed amounts of pollutants from soils were determined using GC-MS. Compared to SOM, the activated carbon exhibited a significantly higher adsorption capacity for tested pollutants. The amended soil was most efficient for removing moderately hydrophobic compounds (log K _ow 4.0–4.4): as little as 0.5% (w/w), carbon addition may extend bioretention medium lifetime by approximately 10–20 years before saturation of these pollutants occurs. The column tests also indicated that released SOM sorb onto activated carbon, which may lead to early saturation of sorption sites on the carbon surface. The desorption test revealed that the pollutants are generally strongly sorbed to the soil particles, indicating low bioavailability and limited biodegradation.

     

壬基酚及其短链聚氧乙烯醚在污泥和土壤中的存在和降解

壬基酚聚氧乙烯醚(NPnEO)是广泛使用的表面活性剂．在污水处理厂中会降解为具有内分泌干扰效应的短链产物和最终产物壬基酚(NP)。剩余污泥是其进入环境的重要途径。介绍了NP和短链NPnEO在污泥中的存在情况、污泥处理过程对其存在的影响、以及这些物质随污泥处置过程进入土壤后的降解。     

不同改性剂改善污泥土工性质的比较研究

选择了泥土、矿化垃圾、粉煤灰和建筑垃圾4种改性剂改性城市污水处理厂污泥(以下简称污泥)。结果表明:(1)随着4种改性剂与污泥的混合比增大,混合物含水率降低。(2)当混合比为0.7(质量比)时,各种混合物的抗压强度都达到50kPa的填埋要求;当混合比为0.3～1.0时,混合物的抗压强度随着混合比的增大呈指数形式增大;比较4种改性剂对抗压强度的增大能力,粉煤灰最强,建筑垃圾次之,泥土和矿化垃圾较弱。(3)在50kPa预压力下,混合物要达到不小于25kPa的抗剪强度,泥土与污泥最小混合比为1.0,矿化垃圾与污泥最小混合比为1.0,粉煤灰与污泥最小混合比为0.7,建筑垃圾与污泥最小混合比为0.7。(4)除加泥土的混合物外,混合物压缩系数随着混合比的增大呈总体下降趋势。(5)粉煤灰除臭效果最好,矿化垃圾次之,建筑垃圾较差,泥土最差。     

热处理和pH调节协同作用下污泥调质过程研究

采用单因素实验和正交实验相结合的方式,考察了不同实验条件参数（温度、pH和反应时间）下,热处理和pH调节对污泥细胞溶出过程的影响。结果表明,污泥溶解性化学需氧量（SCOD）与反应温度、溶液pH、反应时间成正相关,其中pH对SCOD的影响最为显著,反应时间对其影响最小。污泥溶胞的最优条件：反应温度120℃,pH=11,反应时间为15 min,经过处理,SCOD可达14 810 mg/L,与总化学需氧量（TCOD）之比为49.29%,总有机碳（TOC）达4 560 mg/L,总氮（TN）则增加27%,总悬浮固体（TSS）和挥发性悬浮固体（VSS）去除率分别达22.85%和40.93%。热碱处理后污泥上清液分子量分布（MWD）状况结果显示：〉1 000 KDa MW物质含量随pH和温度的增加而增加,当pH=11时,该部分物质可从原污泥的20.94%增加到31.70%;当温度为120℃时,该部分物质可达49.83%。     

Biodegradation of nonylphenol in sewage sludge

We investigated the effects of various factors on the aerobic degradation of nonylphenol (NP) in sewage sludge. NP (5 mg/kg) degradation rate constants (k₁) calculated were 0.148 and 0.224 day⁻¹ for the batch experiment and the bioreactor experiment, respectively, and half-lives (t_1/2) were 4.7 and 3.1 days, respectively. The optimal pH value for NP degradation in sludge was 7.0 and the degradation rate was enhanced when the temperature was increased and when yeast extract (5 mg/l) and surfactants such as brij 30 or brij 35 (55 or 91 μM) were added. The addition of aluminum sulfate (200 mg/l) and hydrogen peroxide (1 mg/l) inhibited NP degradation within 28 days of incubation. Of the microorganism strains isolated from the sludge samples, we found that strain CT7 (identified as Bacillus sphaericus) manifested the best degrading ability.     

Dioxins and furans formation in pilot incineration tests of sewage sludge spiked with organic chlorine

The factors affecting polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) formation were studied in sewage sludge incineration tests carried out on a demonstrative plant. The plant includes a circulating fluidised bed furnace (FBF) and a rotary kiln furnace (RKF), operating alternatively. During the tests sewage sludge was spiked with chlorinated hydrocarbons and the operating parameters of the afterburning chamber were varied. PCDD/F were sampled in each test before the bag filter, thus collecting the above contaminants before abatement systems. From the tests it appeared that PCDD/F were always produced in more abundance in the tests carried out by FBF than by RKF. The higher PCDD/F concentrations in the tests by FBF were reached when sewage sludge was spiked with a high dosage of a surrogate organic mixture of chlorinated hydrocarbons and when the afterburning chamber was used only as transit equipment with the burner off. The distribution of the different PCDD/F homologues was compared. P5CDFs were generally the prevalent fraction, with very few exceptions for the tests by RKF at high temperature of the afterburning chamber. As for FBF tests, it was found that the PCDD/F homologue profile depends on the afterburning chamber temperature.     

Pyrolytic characteristics of sewage sludge

In this study, a number of different sewage sludge including sludge samples from industrial and hospital wastewater treatment plants were characterized for pyrolysis behavior by means of thermogravimetric analysis up to 800 degrees C. According to the thermogravimetric results, five different types of mass loss behaviors were observed depending on the nature of the sludge used. Typical main decomposition steps occurred between 250 and 550 degrees C although some still decomposed at higher temperatures. The first group (Types I, II and III) was identified by main decomposition at approximately 300 degrees C and possible second reaction at higher temperature. Differences in the behavior may be due to different components in the sludge both quantitatively and qualitatively. The second group (Types IV and V), which rarely found, has unusual properties. DTG peaks were found at 293, 388 and 481 degrees C for Type IV and 255 and 397 degrees C for Type V. Kinetics of sludge decomposition can be described by either pseudo single or multicomponent overall models (PSOM or PMOM). The activation energy of the first reaction, corresponding to the main pyrolysis typically at 300 degrees C, was rather constant (between 68 and 77 kJ mol(-1)) while those of second and third reactions were varied in the range of 85-185 kJ mol(-1). The typical order of pyrolysis reaction was in the range of 1.1-2.1. The pyrolysis gases were composed of both saturated and unsaturated light hydrocarbons, carbon dioxide, ethanol and chloromethane. Most products, however, evolve at a quite similar temperature regardless of the sludge type.