Analysis of the chosen thermal and flammability parameters of dried sewage dust

The hazardous sludge disposal process in the form of landfills requires the determination inter alia of the flammable and explosion properties of dried sewage sludge dust, which has the ability to ignite and spontaneously combust when stored in silos. At a constant furnace surface temperature, the minimum ignition temperature of the sludge dust layer with a layer thickness of 5 mm is 270 °C, and for a layer thickness of 12.5 mm it is 250 °C. Two selected fire extinguishing powders for Class A, B, C and D fires were used in the study to determine the possibility of reducing the susceptibility of dried wastewater to ignition from heated surface, self-ignition and explosion parameters. The most effective extinguishing powder was ABC Favorit, which increased the value of the minimum ignition temperature of the layer (5 mm thick) to 360 °C and the spontaneous ignition temperature of the sludge with this powder increased by 22 °C at 169.6 cm³ in comparison to the sludge without extinguishing powder, respectively. The lowest self-ignition temperature of 136 °C was recorded for the largest tested volume (169.6 cm³) for dried sewage dust without any fire extinguishing powders. The biggest values of p_max and (dp/dt)_max dried sewage dust were recorded 4.8 bar and 113 bar/s respectively. By analysing the obtained test results, it can be assumed that dried sewage dust is a combustible material with properties similar to biomass.     

南京市城市污泥和工业污泥中典型矿质元素含量和形态分布研究

采用三态连续提取法研究南京市部分城市污泥和工业污泥中典型矿质元素的含量和形态分布,为污泥资源化的合理利用提供科学参考.结果表明,污泥总体呈高有机质、高氮磷、低K的相似性,但其理化性质如阳离子交换容量(CEC)、pH等有差异.污泥中不同矿质元素含量差异也较大,Fe的浓度最高,其次是Mg、Zn;且不同污泥间同一矿质元素含量的差异也较大.各元素的形态分布有一定差异,Cu主要分布在可氧化态,其酸溶/交换态和可还原态的百分率很低;Zn三态分布均较高;Mg、Mn主要分布在酸溶/交换态;Fe主要分布在残渣态.但三种提取形态百分率之和除Fe外均超过50%.研究同时表明,城市污泥和工业污泥中矿质元素形态分布无显著性差异.     

Drop in dry mass and organic substance content in the process of autothermal thermophilic aerobic digestion

This paper presents the results of a study of a sludge subjected to the (ATAD) process – Autothermal Thermophilic Aerobic Digestion occurring in a two-stage installation operated in a municipal wastewater treatment plant in Olecko, Poland. The study of the sludge and the analysis of obtained results were conducted over 2011 and 2014. The subject of the study was a thickened sludge in an intermediate tank from which it was next transferred to facility reactors. The stabilization of processed sludge was evaluated analyzing the change in the dry mass (DS) content in the sludge. Measurements were carried out in thickened sludge samples and after the ATAD process. Collected results were then subjected to a statistical analysis and it was determined to which extent as resulted from the subject process the dry mass and the dry organic mass (VS) content was changing in the sludge. Also, it was analyzed how the oxygen chemical demand (COD) was changing. The dry mass content in the thickened sludge was from 60 g/l to 160 g/l. After the process, this amount was from 35 to 76 g/l. Similarly, the organic mass content in a dry sludge mass changed from initial values within a range of 44–135 g/l to 23–60 g/l after the ATAD process. Also, the organic substance content expressed as COD decreased from 80 to 467 g O₂/l in a thickened sludge to 51–261 g O₂/l in the sludge after the process. The article presents conclusions from the result of the conducted study as well as personal experience.     

Mass balance of anionic surfactants through up-flow anaerobic sludge blanket based sewage treatment plants

The outcome of a 21-month monitoring study on anionic surfactants (AS) at five (27–70 ML/d) up-flow anaerobic sludge blanket (UASB) based sewage treatment plants (STPs) is described. The average removals of AS were around 8–30%. Appreciable concentrations of AS were being discharged to the watercourse (average 4.30 mg/L; range 3.60–4.91 mg/L). On an average dried sludge contained 1452 mg AS/kg dry weight. Mass balance at three STPs indicated that, AS load of the order of 5–17% and ≈12% is removed by adsorption in UASB reactors and polishing ponds (PP) respectively. Biodegradation of AS under anaerobic conditions in UASB reactors and PP does not seem to take place. In the sludge stream, appreciable biodegradation (≈46%) of adsorbed AS under aerobic conditions on the sludge drying beds takes place. If influent AS mass flux is normalized to 100 units, than average of ≈74 and ≈7 units are discharged with treated effluent and dried sludge respectively, while 12 and 6 units are adsorbed/settled in PP and aerobically biodegrade on sludge drying beds respectively. At two STPs (34 and 56 ML/d), the filterable fluxes in UASBR increased so that the mass balance could not be computed.     

城市污泥微波干化及污染物析出特性研究

采用直接热干化和微波两种方法对3种城市污泥进行了研究,分别考察了温度、污泥厚度、微波功率对干化过程的影响,并研究了干化气体的二次污染问题。研究表明,直接热干化耗时长,温度和污泥厚度是影响干化过程的主要因素;微波干化耗时短,效率高;厚度为4 mm的污泥在微波功率为1 200 W时,仅需3min含水率降至10%以下。微波干化气体的冷凝液COD,NH_4~+-N指标明显低于直接热干化。     

Water treatment sludge for phosphate removal from the effluent of UASB reactor treating municipal wastewater

Aluminium-based water treatment sludge was used as a coagulant for removing/recovering phosphate from the effluent of upflow anaerobic sludge blanket (UASB) reactor treating municipal wastewater. The effect of three variables, namely sludge dose, initial pH and fresh coagulant (poly-aluminium chloride, PACl) dose was studied using response surface methodology. About 87% phosphate removal could be obtained at the optimum conditions of sludge dose 13.8 g/L, initial pH 6, and fresh PACl dose 5.8 mg Al/L. In order to achieve a similar phosphate removal, a dose in the range of 30–40 mg Al/L of fresh PACl was required. The results suggest that water treatment sludge can be reused as a coagulant for post-treatment of UASB reactor effluent treating municipal wastewater and can be considered as a promising alternative for removing phosphate which can substantially reduce the consumption of fresh PACl. The sludge generated during this process could potentially be used in land application which results in recycling of phosphate.     

电絮凝技术处理洗车废水试验

采用电絮凝技术处理洗车废水,以保证处理后出水能够循环利用。考察电流密度、初始pH值、NaCl浓度及电解时间等操作因素对COD与浊度去除效果的影响。结果表明,在最佳处理条件下,出水达到生活杂用水水质标准;另外,去除COD过程符合一级动力学模型,去除单位浓度COD产生4.02×10-3kg湿污泥、3.10×10-4kg干污泥。     

活性污泥法的动力学方程讨论及数学模型研究

活性污泥法水处理过程是一个复杂的生化反应过程,伴随有物理化学反应、生化反应、相变过程及物质与能量的转化和传递过程.通过对微生物动力学方程的讨论,进而建立动力学模型,比较了Monod方程和Contois方程分别来模拟有机碳在曝气条件下的生化去除过程.模型主要预测底物浓度、溶解氧、微生物增长等引起的系统响应,为污水处理厂的运行提供指导.     

铁路物流中心海产品高污染有机污水处理工艺研究

通过海产品加工生产污水处理站“设计施工系统联调联试”的全过程,对其污水性质及特点进行分析,采取以“气浮+ICER生化”为核心的污水处理工艺,结合污水处理系统联调联试,从提温降盐、确定混凝剂投放量及活性污泥培养驯化等方面进行工艺改进,以确保污水达到《污水综合排放标准》(GB 89781996)二级标准。     

UASB+SBR工艺处理皂素生产废水的快速启动研究

皂素生产废水为难处理高浓度酸性含硫有机废水.其中高含量的硫酸盐在厌氧条件下产生大量的H2S,造成了对厌氧微生物的抑制作用,严重影响厌氧生物处理的效果,甚至使厌氧消化完全失败,使该类废水的处理较为困难.为了有效解除硫酸盐对生物处理设施中微生物的抑制,找出皂素生产废水的快速启动运行的方法,本文选用了UASB SBR组合工艺进行了2个月左右的动态连续流实验,对硫酸盐抑制的解除方法进行了研究,提出了相应的解除硫酸抑制厌氧消化的方法,找到了UASB快速启动的有效方法.小试连续运行实验结果表明,在UASB中加入适量铁屑和活性炭颗粒,以生活污水处理厂剩余污泥为种泥可以成功实现UASB SBR处理系统的快速启动,消除DO2-4对生物处理系统的影响,并在较短的时间内(21 d左右)培养出了厌氧颗粒污泥.UASB启动后,在进水COD质量浓度34 000mg/L左右时,COD的去除率一直保持在95%以上,出水COD质量浓度维持在1 300 mg/L左右.厌氧出水经过SBR处理后,出水水质达到了<综合污水排放标准>中的二级排放标准要求.该快速启动方法可供类似酸性高浓度有机废水处理和调试参考.     

Effects of heavy metals on planting watercress in kailyard soil amended by adding compost of sewage sludge

Mixture of sewage sludge with organic garbage was alternatively composted by aerobic and anaerobic technology for 60 days. A basin-scale experiment was performed by planting watercress with kailyard (KY) soil amended with the compost. The results show that average total organic carbon (TOC) increases from 98.45% to 787.69%, and average total nitrogen (TN), total phosphorus (TP) and total potassium (TK) increases to 98.53%, 27.34%, and 41.62%, respectively. The results of watercress in 6 pot experiments with a control treatment show that biomass production increases from 76.47% to 312.00% with the increase of addition of compost from 50 g to 150 g per pot but decreases from 312.00% to 102.29% with the addition of compost to soil and further increases from 150 g to 400 g per pot. The optimal amount of compost added to KY soil is 0.4 g of compost 1 kg of KY soil. Heavy metals accumulated by watercress demonstrate that Cu, Ni, Cd, Pb, Cr, Zn in the crop are much lower than the limited levels of Chinese criteria for vegetables. KY soil is proper to be amended with compost of sewage sludge without threat of bio-magnification of heavy metals to planting watercress.     

Evaluation of decentralized treatment of sewage employing bio-contact oxidation reactor integrated with filter bed

A bio-contact oxidation reactor integrated with filter bed (COR-FB) was developed for decentralized treatment of sewage, which consisted of a biofilm reactor and a gravitational filter bed. It has been investigated to treat municipal wastewater for reuse. The evaluation of COR-FB performance demonstrates that it produced good quality effluent regarding carbonaceous compound, nitrogenous compound, suspended solid and fecal coliform. The efficiencies of COD, NH₄⁺-N, TN, TP and turbidity removal were 90.7%, 81.4%, 64.6%, 60.1% and 96.7%, respectively. The residual geometric mean of fecal coliform counts in the final effluent of COR-FB was only 7.8 × 10³ MPN/10³ ml, corresponding to removal value of 3.8 log 10. However, TP removal indicates the necessity of an addition of a bagger and mud valve or an enhanced chemical phosphorus removal prior to treated water reuse. Microfauna communities were monitored in COR-FB, which was found to contain 5 genres and 19 species in the biofilm layer. Also, a simple kinetics model for COR-FB was developed based on the influent, effluent soluble COD concentration and the reaction time by regression simulation. In general, available data proved that COR-FB system can be recommended as a compact and cost-effective technology for decentralized treatment of sewage, especially for developing countries.     

活性污泥吸附预处理腈纶废水的机理研究

以活性污泥作为吸附材料,研究了其对腈纶废水COD的吸附特征。结果表明,活性污泥可吸附腈纶废水中的COD,吸附量可达135 mg/g。伪二级动力学方程能很好地描述活性污泥对腈纶废水中的COD的吸附过程,模型计算出的二级吸附速率常数(k2)为2.3×10-4g/(mg·min);Langmuir方程最适合描述该吸附过程,决定系数在0.96以上。从活性污泥吸附前后腈纶废水中的有机物相对分子质量分级结果可以看出,活性污泥对大分子(30 k Da)有机物有较好的去除,污泥的电镜照片也证明了该点。研究表明,活性污泥吸附可去除腈纶废水中的悬浮物和胶体物,是有效的腈纶废水预处理方法。     

Performance of a pilot scale up-flow septic tank for on-site decentralized treatment of residential wastewater

The aim of this research was to study the on-site anaerobic treatment of a medium-strength residential wastewater in a pilot-scale up-flow septic tank (UST). The effects of three different hydraulic retention times (HRTs) of 24, 12 and 6 h on the UST performance were investigated. The UST removed 85, 77, and 86% of biochemical oxygen demand (BOD₅), chemical oxygen demand (COD) and total suspended solids (TSS), respectively, at steady state operation and with a 24 h HRT. Decreasing the HRT to 12 and then 6 h resulted in deteriorated effluent quality and significantly reduced reactor performance. The sludge showed a high specific methanogenic activity (SMA) of 15.2 mL CH₄ g^?1 VSS d^?1 with raw wastewater substrate. The solids accumulated in the tank by the end of the experiment had a VSS/TSS of 0.57, demonstrating significant stabilization. Overall, the UST is concluded to be a technically and economically promising alternative to conventional septic tanks for the on-site decentralized treatment of residential wastewater, particularly in the rural communities of developing countries.     

Extraction of phosphorus compounds from ashes from thermal processing of sewage sludge

The experimental results on the influence of temperature on the combustion process of sewage sludge, physicochemical properties of the produced ash, as well as the course of selective extraction of phosphorus compounds from the ashes with nitric acid, are presented. The selective leaching of phosphorus compounds with limited transfer of ferrous ions into solution was possible as a result of formation of sparingly soluble in nitric acid hematite phase in calcined ashes. Temperature 950 °C of thermal processing of ash was found to be mostly advantageous for selective extraction of phosphorus compounds from the ashes with nitric acid.     

Biohydrogen production using waste activated sludge as a substrate from fructose-processing wastewater treatment

Biohydrogen production by dark fermentation in a series of batch tests under different environmental control conditions was evaluated to determine the optimal initial cultivation pH and temperature for a continuous-flow kinetic test to validate the kinetic model system. The waste activated sludge (WAS) from fructose-processing manufacturing was used as the model substrate for biohydrogen production. The batch experiments for biohydrogen production were conducted in a 6 l bioreactor. Fifteen batch kinetic tests were investigated when pH was controlled at 6, 7, 8 and 9 as well as the temperature was controlled at 37 °C, 45 °C and 55 °C, respectively. The experimental results indicated that the optimal operational condition for hydrogen production occurred while pH was 7 and temperature was 55 °C with the highest hydrogen production of 7.8 mmol. The optimal recovery time for hydrogen was 25 h in the batch experiments. Furthermore, the kinetic test of biohydrogen production was performed by anaerobic mixed microbial culture in the continuous-flow experiment when pH and temperature was maintained at 7 and 55 °C. Approximately 60% and 7% of substrate solution was converted into acetate and hydrogen, respectively, at the steady state. Roughly only 0.77% and 2.7% of substrate solution was converted into propionate and butyrate, respectively, at a steady-state condition. The experimental and modeling approaches presented in this study could be employed for the design of pilot-scale and full-scale anaerobic biohydrogen fermentors using food-processing waste activated sludge (WAS) as a substrate solution.     

污泥对水稻分蘖及产量形成影响的研究

为探讨工业废水处理后的污泥能否在农业上应用,以哈药集团制药总厂经生物处理产生的污泥为材料,研究水稻分蘖动态及产量形成.结果表明,该厂排放的污泥,有机质和速效氮、磷含量高,施入土壤后能迅速被水稻吸收利用.适量施用污泥,水稻返青加快、分蘖增多,体内叶绿素含量增高,同时水稻的产量也得到提高.污泥施用过量,会导致水稻返青率降低,后期分蘖无法控制,导致生育延迟,空秕粒率大幅度增高,产量显著下降.     

Disintegration of waste activated sludge by different applications of Fenton process

Oxidative disintegration of municipal waste activated sludge (WAS) using conventional Fenton (Fe²⁺ + H₂O₂, CFP) and Fenton type (Fe⁰ + H₂O₂, FTP) processes was investigated and compared in terms of the efficiency of sludge disintegration and enhancement of anaerobic biodegradability. The influences of different operational variables namely sludge pH, initial concentration of Fe²⁺ or Fe⁰, and H₂O₂ were studied in detail. The optimum conditions have been found as catalyst iron dosage = 4 g/kg TS, H₂O₂ dosage = 40 g/kg TS and pH = 3 within 1 h oxidation period for both CFP and FTP. Kinetics studies were performed under optimal conditions. It was determined that the sludge disintegration was happened in two stages by both processes: rapid and subsequent slow disintegration stages and rapid sludge disintegration stage can be described by a zero-order kinetic model. The effects of oxidative sludge disintegration under the optimum conditions on anaerobic digestion were experienced with biochemical methane potential (BMP) assay in batch anaerobic reactors. Total methane production in the CFP and FTP pre-treated reactors increased by 26.9% and 38.0%, relative to the untreated reactor (digested the raw WAS). Furthermore, the total chemical oxygen demand reductions in the pre-treated reactors were improved as well.     

生活污泥干化与生活垃圾协同焚烧研究分析

我国城市化的快速发展导致城市人口的迅速膨胀,城市生活污水产生量也迅速增加,在污水处理过程中自然而然的产生了大量的污泥。据不完全统计,每年一座中等城市产生的污泥量大约在25~30万t。本文通过对生活污泥干化的研究与生活垃圾协同焚烧的研究,有助于形成积极的公众舆论和认同,为垃圾协同污泥焚烧技术在全国的推广实施提供便利。