Influence of the Nature of the Incoming Sludge on the Performance of a Vertical Flow Reed Beds in Dakar-Senegal

This work investigates the influence of the type sludge on drainage, plant development, purification performances and biosolids quality. Drainage properties were measured through the frequency of clogging, the percentage of leachate recovered and the dryness of accumulated sludge. Plant development was measured through the density, the height and the stem diameter. Purification performance was evaluated from the reduction rate. Biosolids quality was measured after 3 months of maturation. The results show that the clogging frequencies were 9.5%;0% and 3.7%;the volume of leachate recovered was 42.2%;20.4% and 24.7% and, the dryness was 33.4%;61.1% and 52.4% for FS-ST, FS-STT and SS respectively. Plants densities were about, with densities 197.1, 171.3 and 178.3 plants/m2 in beds fed respectively with FS-ST, FS-STT and SS. Despite the high removal rates, the concentrations of pollutants in the leachates are above the Senegalese standard NS 05-061 for discharge into the environment. The biosolids are all mature with C/N and NH4+/NO3?ratios lower than 12 and 1 respectively. The biosolids are also rich in organic and mineral elements. The concentrations of Ascaris eggs are higher than the WHO recommendations. These biosolids should be stored for additional time or composted.

Emission characteristics of dioxins,furans and polycyclic aromatic hydrocarbons during fluidized-bed combustion of sewage sludge

Pre-dried sewage sludge with high sulfur content was combusted in an electrically heated lab-scale fluidized-bed incinerator. The emission characteristics of polychlorinated dibenzo-p-dioxins （PCDDs）, polychlorinated dibenzofurans （PCDFs） and polycyclic aromatic hydrocarbons （PAHs） were studied. Coal and calcium oxide （CaO） were added during the sewage sludge combustion tests to optimize combustion conditions and control SO2 emission. The results indicated that the flue gases emitted during mono-combustion of sewage sludge were characterized by relatively high concentrations of SO2, NOx and organic pollutants, due to the high sulfur, nitrogen, and volatile matter content of sewage sludge. The total 16 USEPA priority PAHs and 2,3,7,8-substituted PCDD/Fs produced from sewage sludge combustion were found to be 106.14 μg/m^3 and 8955.93 pg/m^3 in the flue gas, respectively. In the case of cocombustion with coal （msludge/mcoal =1：1）, the 16 PAHs and 2,3,7,8-substituted PCDD/Fs concentrations were markedly lower than those found during mono-combustion of sewage sludge. During co-combustion, a suppressant effect of CaO on PCDD/Fs formation was observed.

Co-Processing Sewage Sludge in Cement Kiln in China

Sewage sludge is the by-product from municipal waste water treatment plant and is highly polluted. How to treat the SS in a solid environmental friendly way is strictly concerned in China. In this article, the SS situation and also the treatment methods in China have been introduced. The advantage and some related issues of co-processing SS in cement kiln have been discussed. The technical model and projects of Huaxin cement for co-processing SS in cement kiln also have been introduced.

Planted Sludge Drying Beds in Treatment of Faecal Sludge from Ouagadougou: Case of Two Local Plant Species

Management of wastewater is a concern of developing countries. In Burkina Faso, an on-site septic system installed on the property is predominant and those systems product high quantities of faecal sludge which are not treated adequately before discharge. Our country is mainly fed by surface water, while water is the main vector of many diseases. So it is very important to manage efficiently wastewater and faeces. The treatment of faecal sludge by planted beds can use local persistent emergent plants like Andropogon gayanus (LPA) and Cymbopogon nardus (LPN). Those planted beds are compared to a non-planted bed (sludge drying bed) (LT). Treating raw sludge (BB) we got the yield over 90% concerning the biological oxygen demand (BOD5) for the LPA while the two others gave performances of 75% and 76% respectively. Regarding the chemical oxygen demand (COD), LPN gave better yields with 77% of removal against 71% and 69% for LPA and LT respectively. Overall, the pilots assured removal of orthophosphates varying between 77% and 79%, while the Kjeldahl nitrogen is removed by the various beds with respective fields of 94%, 96.5% and 97.5% for LPN, LPA and LT. The microbiological pollution abatement is in the order of 1 log unit on average for all beds.

Drying Kinetics of Paper Mill Sludge

Drying experiments of two paper mill sludge were carried using hot air with a temperature range of 50?C - 80?C and an air velocity of 0.96 m/son a laboratory convective dryer. The drying characteristics were discussed and the drying kinetic equation was solved. The dependence of the reaction rate constant on the drying temperature was given by Arrhenius equation, and the activation energies for moisture diffusion in paper mill sludge sample A and B were found to be 21.53 kJ/mol and 15.38 kJ/mol, respectively.

Sludge Drying and Incineration Method Applied to Sludge Reduction Research

This work takes sludge drying and incineration and pollutant discharge characteristics as the main line of research.With sludge dewatered by a certain sewage plant in southern Jiangsu using machinery and chemical conditioners selected as the research object,the influencing factors such as particle size,drying temperature and sludge reverse-mixing ratio in the sludge drying process were mainly explored,and the best working conditions of sludge drying were further analyzed.On this basis,in-depth research was carried out on the pollutants such as NO_(x),SO_(2),HCl,CO and other pollutants generated in the sludge incineration process by investigating the incineration temperature,sewage,the sludge moisture content and excess air coefficient.The results showed that the best conditions for sludge drying were as follows:particle size 3.5 mm,temperature 210℃and reverse-mixing ratio 25,and the cumulative drying time of the sludge 445.21 min.Through the research on the pollutant emission characteristics of sludge incineration,it was found that the incineration temperature and the moisture content of the sludge had a greater impact on the emission concentrations of NO_(x),SO_(2),HCl,and CO.Among them,the incineration temperature was the key factor that affected the generation of NO_(x),SO_(2),HCl,and CO.

Use of Borax Sludge as an Additive in Wall Tile

In this research, the use of borax sludge, which is generated in borax industry, as an additive in wall tile, was investigated. The wall tile samples were prepared by adding boron waste to the wall tile composition in the range of 2% - 10%. The effect of boron waste on the physical and mechanical properties of wall tile was determined. The results obtained were compared with the control tile and Turkish Standards (TS). The boron waste addition up to 8 wt.% was found to improve the water absorption and strength of wall tile.

Unsaturated Flow Drying Bed(UFDB):An Alternative for Treatment of Septic Tanks Sludge

Unsaturated Flow Drying Bed (UFDB) principles are based on the ones of wastewater treatment by infiltration-percolation on the one hand and septic tanks sludge solar-drying beds on the other hand. With UFDB, sludge charges are split with low heights, leading to the drying of suspended solids in 2 days, and the infiltration of the flow of liquid in unsaturated middle. For average charges reaching 12.5 cm/d, the treatment efficiency of total oxygen demand and Total Kjeldahl Nitrogen, respectively 95 and 96%, correspond to a treatment capacity of 0.5 kg of O2/d/m2 of drying area. Bacteria reductions of 4 Ulog are obtained from filtrates outlet, with average fecal coliforms charges less than 103 CFU/100 ml. Monitoring the hydrodynamic behavior through rates, moisture, organic matter and respiratory activity demonstrates that the clogging of the massifs is linked to a biofilm growth within them. A four week resting period allows biofilm resorption. Thus, the drying of the infiltration surface in two days, the elimination of carbon, nitrogen and bacterial pollutions, as well as the reversibility of clogging show that UFDB is a credible alternative for the treatment of septic tank sludge in the socio-economic context and climate of tropical Africa.

Drainage Bed:A Natural System for WTP Sludge Dewatering and Drying with Different Coagulant Chemicals in Tropical Countries

This study seeks to evaluate the mechanisms for dewatering sludge from Water Treatment Plants (WTP) in a natural system that uses nonwoven polyester geotextile blankets named Drainage Bed (DB). Dewatering mechanisms are divided into two stages: Drainage and Drying Phases. For the Drainage Phase, the results showed that the solids content of the Aluminum Sulfate sludge reached 8.9% to 18.3% and the PACl sludge 1.8% to 6.5%, the volume reduction on this phase exceeding 50% and 74%, respectively. The final solids content, after the Drying Phase, was greater than 28%, reaching 90%. In the Drainage Phase the lower the Surface Application Rate—SAR [kg/m2] is, the greater the drainage flow will be. In the Drying Phase, moisture and insolation were key factors in drying sludge. Thus, the Drying Phase in the DB takes special attention for being virtually nonexistent in dewatering technologies in a closed system (confined) without exposure to solar energy. The use of the DB as a natural system for dewatering WTP sludge in tropical countries proved to be a promising alternative, because of its efficient removal of water from sludge coupled with operational simplicity and low costs, provided there is area available.

Agricultural Soil Fertilizing Potential of Dry Faecal Sludge from Treatment Plants in Burkina Faso

The dry faecal sludge (DFS) are potential sources of organic fertilizers because of their high content in nutrients and organic matter, critical for plants growth and soil health maintaining. In Burkina Faso, the DFS are processed in faecal treatment plants. However, after drying, the DFS are most often dumped in the nature without any control or directly used as fertilizer without any idea of their potential risks for human health and the environment. This investigation aimed at physico-chemical and toxicological characterization of the DFS from faecal treatment plants according to the duration of their storage. For this purpose, DFS samples were collected in three (3) faecal treatment plants in Ouagadougou and one in Bobo Dioulasso, in Burkina Faso. The measurements were carried out on pH (H2O), organic matter content, major nutrients (N, P, K), trace elements (Na, Ca and Mg) and metallic trace elements. Indifferently to the faecal treatment plants and the duration of the storage, the DFS showed strong acidity (4.85 ± 0.13 et 6.53 ± 0.10) and low content in total elements (Na à40.97% ± 9.99%). Values recorded of the trace metallic elements showed there were no risk of contamination when used as fertilizers: (103.9 ± 2.00 mg/kg < Cu < 137 ± 25.69 mg/kg);(710.13 ± 18.97 mg/kg < Zn < 922.30 ± 7.04 mg/kg);(33.03 ± 1.65 mg/kg < Pb < 152.40 ± 19.40 mg/kg);(1.34 ± 0.17 mg/kg < Cd < 1.76 ± 0.04 mg/kg);(34.34 ± 0.27 mg/kg < Ni < 52.32 ± 3.60 mg/kg) et (771.15 ± 18.36 mg/kg < Cr < 1697.83 ± 55.11 mg/kg). The results indicated a high fertilizer potential of the DFS after addressing the issue of their acidity.

新型蒸压加气混凝土砌块性能研究

基于容重轻、强度高以及成本低的新型蒸压加气混凝土砌块,通过分析脱硫渣、陶瓷抛光废料、煤化工业固体以及工程泥浆干化泥的化学成分和基本性能,研究了上述工业废弃物制备的新型蒸压加气混凝土的各项基本物理力学性能及其应用前景,合理配合比下的新型蒸压加气混凝土砌块的各项技术指标满足建筑材料的标准要求,存在较为可观的潜在应用前景,对推动建材绿色循环利用具有重要意义。

Atmospheric emission characterization of a novel sludge drying and co-combustion system

A novel system combining sludge drying and co-combustion with coal was applied in disposing sludge and its atmospheric emission characteristics were tested. The system was composed of a hollow blade paddle dryer, a thermal drying exhaust gas control system, a 75 tons/hr circulating fluidized bed and a flue gas cleaning system. The emissions of NH3, SO2, CH4 and some other pollutants released from thermal drying, and pollutants such as NOx, SO2 etc. discharged by the incinerator, were all tested. Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans （PCDD/Fs） in the flue gas from the incinerator were investigated as well. The results indicated that the concentrations of NOx and SO2 in the flue gas from the incinerator were 145 and 16 mg/m^3, respectively, and the I-TEQ concentration of 2,3,7,8-substitued PCDD/Fs was 0.023 ng I-TEQ/Nm^3. All these values were greatly lower than the emission standards of China. In addition, there was no obvious odor in the air around the sludge dryer. The results demonstrated that this drying and co-combustion system is efficient in controlling pollutants and is a feasible way for large-scale treatment of industrial sludge and sewage sludge.

Heavy Metal Migration Characteristics of Co-Combustion between Sewage Sludge and High Alkaline Coal on Circulating Fluidized Bed

The migration characteristics of heavy metals in co-combustion of sewage sludge and high alkali coal in circulating fluidized bed were studied by experiments and simulations. Temperature plays a crucial role in thermodynamic equilibrium distribution and migration characteristics of heavy metals. At the temperature range of 700℃-1200℃, Hg is completely gaseous and the proportion of Pb, Ni, and Cd in the gas phase is also high. As is mainly elemental in the system, and the proportion of Cr in the solid phase is large. Zn compounds are diverse and mostly solid materials. The volatility of Cu is not strong, and it will become gaseous when the temperature exceeds 1700℃. The proportion of heavy metals in the gas phase decreases as the excess air ratio increases. In an oxygen-rich atmosphere, most of Zn and Ni are converted to oxides;Pb and Cd are converted to crystalline silicate;Cu is converted to partial aluminate;Cr compound is decomposed to form Cr_(2)O_(3);they are good for the solidification and controlling of heavy metals. The elemental Hg is converted to HgCl_(2) and the elemental As is converted to AsCl_(3). Temperature also has a great influence on the volatilization rate of heavy metals. The higher the temperature, the shorter the time they reach the maximum volatility.

Investigating the co-combustion characteristics of oily sludge and ginkgo leaves through thermogravimetric analysis coupled with an artificial neural network

The co-combustion characteristics of oily sludge and ginkgo leaves(GL) in an oxy-fuel atmosphere are investigated via thermogravimetric analysis coupled with an artificial neural network. The combustion characteristics of blends improve as the GL mass ratio increases. The interaction indices used to evaluate the interaction between the two solid combustibles present a complex nonlinear relationship in different stages. The Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods are used to calculate the activation energy of the blends, which increases with an increase in the oxygen concentration, in different atmospheres. Compared with the radial basis function, the backpropagation neural network performs better in predicting the combustion curve of the blends.

Evaluation of PCDD/Fs and metals emission from a circulating fluidized bed incinerator co-combusting sewage sludge with coal

The emission characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans （PCDD/Fs） and heavy metals were evaluated during co-combustion of sewage sludge with coal from a circulating fluidized bed incinerator. The stack gas, slag and fly ash samples were sampled and analyzed. The gas-cleaning system consisted of electrostatic precipitators and a semi-dry scrubber. Results showed that the stack gas and fly ash exhibited mean dioxin levels of 9.4 pg I-TEQ/Nm3 and 11.65 pg I-TEQ/g, respectively, and showed great similarities in congener profiles. By contrast, the slag presented a mean dioxin level of 0.15 pg I-TEQ/g and a remarkable difference in congener profiles compared with those of the stack gas and fly ash. Co-combusting sewage sludge with coal was able to reduce PCDD/Fs emissions significantly in comparison with sewage sludge mono-combustion. The leaching levels of Hg, Pb, Cd, Ni, Cr, Cu, and As in the fly ash and slag were much lower than the limits of the environmental protection standard in China. These suggest that the co-combustion of sewage sludge and coal is an advisable treatment method from an environmental perspective.

水泥窑协同处置城市干化污泥技术及其工程化应用

广州越堡水泥协同处置城市干化污泥项目采用“污水处理厂内干化+水泥窑协同处置”技术路线,市政污泥经污水处理厂深度脱水+电热干化后,污泥最终含水率降至40%以下;干化污泥再经协同处置系统卸料、输送、破碎、喂料、除尘除臭,处置城市干化污泥量达600t/d,折算处置含水湿污泥约1 800t/d,技术优势明显。污泥处置系统运行以来,二噁英排放量为0.037ng TEQ/m~3,远低于国家标准排放限值0.1ng TEQ/m~3;年节煤约4.4万吨,节煤收益>3 750万元,按照吨烟煤排放CO_(2) 2.0t估算,年可减排CO_(2)约8.8万吨。

Multifractal characteristics of cylindrical sludge drying

This paper analyzes dewatered sludge drying using the multifractal theory.The drying rates of cylindrical sludge with equal masses but different crosssectional diameters was studied,from which multifractal parameters such as partition function and quality exponent were obtained.The parameters acquired were used to calculate the multifractal singularity spectrum and indicate the presence of multifractal characteristics.The smaller cross-sectional diameters of the sludge were found to be non-homogeneous,and required quantitative methods to analyze.

转底炉金属化球团热装热送技术研究

介绍了对宝钢股份宝山基地2号转底炉金属化球团热装热送技术。该技术的应用,解决了热取料、热料运输和热装料过程中产生的金属化球团氧化、板结及冒烟等问题,使得热态金属化球团可以不需冷却直接被作为废钢原料加入鱼雷罐中,对企业节能降碳具有积极的推动作用。

污泥作为添加剂制备轻质陶粒的试验研究

干污泥作为原料之一制作陶粒是一种有效的污泥处置方法.试验中选用干污泥、粘土和粘结剂作为主要原料,得到了制备陶粒最佳成分配比和最佳工艺条件是污泥添加量为100%(与粘土质量比)、粘结剂添加量为20%(与粘土质量比)、烧成温度为950℃、保温时间为20 min;产品的主要性能指标是松散容重为519 kg/m3,颗粒表观密度为1110 kg/m3,吸水率为19.6%,空隙率为53.2%.并讨论了原料在烧制过程中的作用、孔隙形成机制和固相反应机理,同时对陶粒进行了物相组成(XRD)和化学成分(XRF)分析.结果表明利用污泥作为添加剂,可以在一定条件下制备出性能优良的陶粒.

染料在干污泥上的吸附平衡和动力学

本文研究了染料活性嫩黄 KD- 3G、直接深棕 M和酸性媒介棕 RH在干活性污泥上的吸附平衡和吸附动力学。结果表明 :所试染料的吸附等温线数据都可用 Freundlich方程描述 ;对于 Langmuir方程 ,只有酸性媒介深棕 RH的等温线数据能与之拟合。染料的吸附过程遵循二级吸附动力学模型 ,也能用 Lagergren一级速率方程描述。在吸附温度为 1 5℃、2 0℃、2 5℃、35℃和 45℃时 ,活性嫩黄 KD-3G、直接深棕 M和酸性媒介棕 RH的一级吸附速率常数分别为 0 .0 0 2 8～ 0 .0 0 3 2 min- 1、0 .0 1 5～ 0 .0 4 0 min- 1、0 .0 0 7～ 0 .0 1 2 min- 1 ,二级吸附速率常数分别为 0 .0 0 0 2 7～ 0 .0 0 0 4 7g/ (mg· min)、0 .0 0 6 5～ 0 .0 2 90 g/ (mg· min)、0 .0 0 3 0～ 0 .0 1 3 2 g/ (mg· min)。由二级吸附速率方程计算得到的平衡吸附量与实验值的相对误差在 1 0 %以内 ,这表明两者的符合程度较高。上述温度范围内 ,当染料质量浓度为50 mg/ L时 ,活性嫩黄 KD- 3G、直接深棕 M和酸性媒介棕 RH的平衡吸附量分别为 1 6.5～ 1 9.2 mg/ g、1 4 .3～ 1 6.0 mg/ g、7.2～ 9.6 mg/g。