Pilot study of intense dewatering of urban sewage sludge

Urban sewage sludge treatment has become a severe problem due to its large quantities and enrichment with heavy metals, refractory organic contaminants and pathogenic bacteria. Accordingly, it is essential to develop an effective and low-cost intense dewatering technique to decrease sludge water content so that it can be easily treated by subsequent incineration, landfilling or composting. In this study, a new intense sludge dewatering technique using conditioner of coagulant and flocculant (polyacrylamide) mixture and the diaphragm filter press was developed and investigated systematically by measuring the water content, calorific value and coliform bacteria in the sludge and investigating the dewatering efficiency under different conditions. The results showed that the water content of the sludge was effectively reduced from 80 % to the minimum of 43.6 % by adding conditioners and subsequent dewatering using the diaphragm press. Moreover, the low calorific value of dewatered sludge increased significantly from that of the original sludge, and was conducive to subsequent incineration. The water content of the dewatered sludge cake decreased to less than 25 % after being kept in the open air for 9 days. Therefore, it is proposed that this technique be applied to large-scale engineering applications.     

Hybrid cement-assisted dewatering,solidification and stabilization of sewage sludge with high organic content

Sewage sludge with high organic content is particularly difficult to dewater before disposal in landfill. In this study, different hybrid cement binders were investigated to evaluate their ability to dewater the sewage sludge with high organic content. After 7 days of stabilization, the CASC (Mayenite/Sulfoaluminate cement) hybrid binder showed an excellent efficiency on both water content reduction and strength development; the water content and unconfined compressive strength value of solidified sludge reached 52.43 % and 109.55 kPa, respectively, at 8 % binder/sludge mass rate. The horizontal vibration leaching test (HJ 557-2009) indicated that leachability of heavy metals of the CASC-solidified sludge was far lower than that of non-solidified sludge and CAPC-solidified sludge. Furthermore, SEM and XRD analyses suggested that certain hydrates formed in the solidification process might have accelerated the depletion of interstitial water and strength development in the CASC-solidified sludge.     

Integrated effects of applied pressure,time, and polymer doses on alum sludge dewatering behaviour

In this study, combinations of applied pressure, pressing time and polymer dose were examined in an air pressure plate apparatus to explore their integrated influence on the dewatering of an alum sludge. Results of the investigation demonstrated that dewatering can be enhanced by increases in pressure and time. However, a point is reached at which continued increases in pressure and time offer little benefit. The data also confirmed that polymer affects the rate of water release rather than the extent of dewatering. Increased rates of water release due to increasing polymer dose can be attributed to the aggregation of sludge particles by polymer addition. It was also evident in this study that the initial sludge depth has a major impact on the average cake moisture content at a given dewatering time. It was apparent that once the initial sludge thickness exceeds about 2 cm, the water release follows a fairly similar pattern, which can be represented by a simple empirical model.     

Phytoremediation of industrial sludge using vegetation‐assisted dewatering

With the emergence of risk‐based corrective action decisions, there is interest in the use of more natural techniques that may be as protective as the traditional removal, landfill, or capping approaches for impoundment closure. The use of phytoremediation is one of the more promising techniques. This article presents the results of a three‐year field‐pilot phytoremediation study that involved the use of plants to enhance sludge dewatering at an inactive natural gas‐cracking wastewater lagoon. The dewatering was accompanied by contaminant reduction of benzene, toluene, xylene (BTX), and naphthalene concentrations to below the cleanup goals. Meanwhile, the concentration reductions of three or more ring polynuclear aromatic hydrocarbons (PAHs) varied between 30 percent and 60 percent, except for dibenz[a,h]anthracene. The residual PAHs in the sludge are not leaching. Parallel laboratory studies suggest a reduced PAH availability and mobility in the unsaturated zone sludge. © 2002 Wiley Periodicals, Inc.     

The effect of the addition of fly ash to municipal digested sludge on its electroosmotic dewatering

Effective handling of municipal digested sludge requires that the product cake have low water content. To this end, we investigated the change in sludge dewaterability after the addition of fly ash to municipal digested sludge, dewatering of which is difficult because of its high organic content. The performance of the dewatering is compared with that of electroosmotic dewatering (EDW) and conventional mechanical dewatering (CMD). Fly ash classified by sieving to the size of 25–75 μm and >75 μm is added to the municipal digested sludge by 10, 20, and 50 wt% by wet base. When adding fly ash particles to municipal digested sludge, dewatering efficiency improved with smaller fly ash particle size and with increase in the amount. When sludge was dewatered using an electroosmotic dewatering method, the dewatering efficiency is improved about 40% by adding fly ash of 25–75 μm particle size with 20 wt% when compared with conventional mechanical dewatering method without adding the fly ash. It is concluded that fly ash particles rich in inorganic material are helpful in the dewatering process when added to municipal digested sludge and EDW is more effective than CDW.     

炼厂浮渣的超声强化脱水处理

针对炼厂浮渣乳化严重、脱水减量困难的问题,采用超声—离心分离工艺对其进行强化脱水处理。比较了单独离心、絮凝—离心和超声—离心3种方式对浮渣的脱水效果,考察了超声时间和超声温度对浮渣脱水效果的影响,表征了超声处理前后浮渣的微观结构,探讨了超声强化脱水的机理。实验结果表明:在未加任何药剂、超声频率25 kHz、超声功率240 W、超声时间5 min、超声温度30℃的最佳工艺条件下,浮渣脱水率为89.68%,较单独离心和絮凝—离心工艺分别提高了7.77和2.99百分点,底泥含水率为82.94%。表征结果显示:超声机械振动作用破坏了固体颗粒空隙和内部沟壑结构,降低了对油滴的吸附,促进了油滴凝并,实现了原油轻质化,说明超声作用可促进浮渣脱水。     

Centrifugal dewatering of blended sludge from drinking water treatment plant and wastewater treatment plant

Journal of Material Cycles and Waste Management - The blended sludge taken from drinking water treatment plant (WTP) and wastewater treatment plant (WWTP) for centrifugal dewatering was proposed....     

Digested wastewater sludge dewatering process using water treatment plants chemical sludge and walnut shell activated carbon powder

Journal of Material Cycles and Waste Management - In this study, the feasibility of employing polyelectrolyte simultaneously by thickened sludge of water treatment plants (STS), water treatment...     

Improvements of nano-SiO2 on sludge/fly ash mortar

Sewage sludge ash has been widely applied to cementitious materials. In this study, in order to determine effects of nano-SiO(2) additives on properties of sludge/fly ash mortar, different amounts of nano-SiO(2) were added to sludge/fly ash mortar specimens to investigate their physical properties and micro-structures. A water-binding ratio of 0.7 was assigned to the mix. Substitution amounts of 0%, 10%, 20%, and 30% of sludge/fly ash (1:1 ratio) were proposed. Moreover, 0%, 1%, 2%, and 3% of nano-SiO(2) was added to the mix. Tests, including SEM and compressive strength, were carried out on mortar specimens cured at 3, 7, and 28 days. Results showed that sludge/fly ash can make the crystals of cement hydration product finer. Moreover, crystals increased after nano-SiO(2) was added. Hence, nano-SiO(2) can improve the effects of sludge/fly ash on the hydration of mortar. Further, due to the low pozzolanic reaction active index of sludge ash, early compressive strengths of sludge/fly ash mortar were decreased. Yet, nano-SiO(2) could help produce hydration crystals, which implies that the addition of nano-SiO(2) to mortar can improve the influence of sludge/fly ash on the development of the early strength of the mortar.     

活性污泥焚烧过程中镍的迁移分布特性

采用管式炉对污水厂活性污泥焚烧过程中Ni的迁移分布特性进行研究。实验结果表明：当污泥掺烧量（污泥质量与煤和污泥总质量的比）为25%时，Ni的挥发率（飞灰与气体中Ni质量的总和与污泥中Ni质量的比）几乎为零，且污泥与煤混合试样的综合燃烧效果最好；当污泥焚烧加入硫化物时，各种硫化物对Ni的残留率（炉渣中Ni的质量与污泥中Ni质量的比）提高能力大小顺序为Na₂S>S>Na₂SO₃>Na₂SO₄；当污泥焚烧加入氯化物时，促使Ni向烟气中迁移，且加入无机氯更易使Ni向烟气中迁移。     

Bioleaching of zinc and aluminium from industrial waste sludges by means of Thiobacillus ferrooxidans

Biological solubilisation of heavy metals contained in two different kinds of industrial wastes was performed in batches employing a strain of Thiobacillus ferroxidans. The wastes tested were: a dust coming from the iron-manganese alloy production in an electric furnace (sludge 1) and a sludge coming from a process treatment plant of aluminium anodic oxidation (sludge 2). The experimental results pointed out the ability of the used strain to maintain the environment, that initially has a pH about 8, at strongly acid conditions (pH 2.5-3.5), producing sulphuric acid that is the chemical agent responsible for the metals solubilisation. At wastes initial concentration of 1%, the percentage of solubilised metals was 76 and 78% for the wastes 1 and 2, respectively, but the lag phase was considerably longer for sludge 2 than for sludge 1, indicating a different affinity of microorganisms for the solid phase. Increasing the initial slurry concentration, the percentage of removed metal reached 72-73% for the sludge 1, while in case of sludge 2, the total amount of solubilized metal progressively decreased. Two kinetic models are proposed to describe the trends of metals solubilization curves.     

Fenton试剂处理汽车油漆废渣

采用Fenton试剂处理汽车油漆废渣。考察了FeSO_4用量、H_2O_2用量、反应温度、反应时间对处理效果的影响。实验结果表明,在FeSO_4用量为20.5 mg/g、H_2O_2用量为0.6 g/g、反应温度为80 ℃、反应时间为3 h的最优条件下,清漆渣、色漆渣、底漆渣3种漆渣的干基减量率均为20%左右,湿基减量率分别为67.9%、48.2%和64.2%,3种产物的脱水性能均有不同程度的提高,处理后废液的COD均为2 000 mg/L左右。采用Fenton试剂处理后的清漆渣产物粒径与原料相似,产物颗粒球形度高,表面粗糙,内部为多孔结构,产物作为固体燃料时燃烧更充分。Fenton试剂处理未对漆渣中的树脂主体产生较大的破坏。     

Thermal behaviour of chromium electroplating sludge

Galvanic sludge is classified as a hazardous waste and incineration is one of the techniques used for its treatment. The aim of this work is to study the thermal behavior of a galvanic sludge which contains only chromium as a restriction metal. Simultaneous DTA/TG coupled with mass spectrometer tests were performed to characterize the thermal behavior of the sludge. Besides thermal analysis, sludge samples were heated in a specially designed furnace and these samples were submitted to X-ray diffraction. Vapor from the heated sludge was condensed and the particles were analyzed by EDS microprobe coupled in a scanning electron microscope. The slag formed after the calcination of the galvanic sludge was mainly composed of a mixture of calcium phosphate and fluoride. and minor concentrations of metals. A total weight loss of 34% was observed. The greatest part of this weight loss corresponds to CO2, H2O and SO2. H2O is liberated in the temperature range of 500-1,250 degrees C. CO2 in the range of 500-750 degrees C and SO2 near 1,000 degrees C. Chromium evaporation was not observed in relevant quantities, about 99.6% of the Cr remained incorporated in the slag.     

Effects of emulsified asphalt on the mechanical properties of granulation of calcium fluoride sludge

Journal of Material Cycles and Waste Management - To reduce the landfill volume of waste CaF2 sludge, artificial fluorite bulk (AFB) is granulated by blending CaF2 sludge and emulsified asphalt...     

Volatility of heavy metals during incineration of tannery sludge in the presence of chlorides and phosphoric acid.

Knowledge of the behaviour of heavy metals in the combustion process is a most important factor in selecting disposal alternatives for waste materials. Accordingly, in this work, the vaporization behaviour of highly concentrated heavy metals (Pb, Zn, Cu and Cr) in tannery sludge were investigated experimentally. The sludge was spiked with various chlorine compounds (i.e. PVC, FeCl3, CaCl2 and NaCl) and pre-treated with phosphoric acid in order to evaluate the capacity of enhancement and weakening of the volatility of the heavy metals contained in tannery sludge. The experimental results show that the vaporization percentages increased with increasing ratio of Cl/sludge and temperature, and the accelerating and increasing effect of the addition of chlorides on the vaporization percentage of heavy metals was dependent on the release capacity of chlorine radicals. The vaporization percentages of lead and zinc increased by 15-20%, whereas those of copper and chromium increased by only about 3 and 10% at 800 degrees C. However, heavy metals were not expected to be completely released in the combustion process in spite of the high ratio of Cl/sludge. Alternately, heavy metals contained in tannery sludge can be immobilized effectively by pre-treatment with phosphoric acid. When the 85% phosphoric acid accounted for 10% of dry basis of tannery sludge, the phosphate-treated sludge showed the lowest vaporization percentage of about 3-15% with formation of Ca18Cu3(PO4)14, Ca9Cr(PO4)7, Ca19Zn2(PO4)14 and PbMgP2O7 in the bottom ash.     

Limitation of the concentration of organic pollutants in sewage sludge for agricultural purposes: A case study in South Spain

In 2000, the EU published the third draft of a future sludge directive entitled “Working document on sludge” where limit values for some organic compounds, including di-(2-ethyhexyl)phthalate (DEHP), sum of nonylphenol (NP), nonyphenol mono-(NP1EO) and diethoxylates (NP2EO), seven polychlorinated biphenyl congeners (PCB), polycyclic aromatic hydrocarbons (PAH) and linear alkylbenzene sulphonates (LAS), are fixed. In the present work, the monitoring of these organic compounds in sludge samples from four wastewater treatment plants (WWTPs) is reported. All WWTPs use anaerobic biological stabilization of sludge. The highest concentration levels were found for LAS, NPE and DEHP, in this order, with, in general, anaerobically-digested dehydrated sludge and compost samples being the most contaminated samples. DEHP, NPE, LAS and PAH were found at concentration levels above the limit values fixed in the third draft of the future EU sludge directive in the 44%, 88%, 13% and 6% of the analyzed anaerobically-digested dehydrated sludge and compost samples.     

城市污泥制备水中重金属吸附剂及其吸附特性研究

本实验利用城市污水厂的脱水污泥,通过化学活化法制备活性炭.研究活化温度、活化时间、固液比和活化剂浓度等因素对制备污泥活性炭的影响,确定氯化锌法制备污泥活性炭的最佳工艺为活化温度550 ℃、活化时间30 min、固液比1∶2、氯化剂浓度45％.将制备的污泥活性炭吸附Cu2＋,Cr6＋,Cd2＋3种重金属离子模拟废水,研究pH值、吸附时间、污泥投加量、温度等因素对吸附过程的影响.实验结果表明,剩余污泥对Cu2＋,Cr6＋,Cd2＋3种重金属离子都具有良好的吸附效果,在优化条件下,3种重金属离子去除率分别达到94％,76％,81％,吸附能力大小顺序为Cu2＋＞Cd2＋＞＋Cr6＋.     

Anaerobic treatment of sludge from a nitrification-denitrification landfill leachate plant

The viability of anaerobic digestion of sludge from a MSW landfill leachate treatment plant, with COD values ranging between 15,000 and 19,400mg O(2)dm(-3), in an upflow anaerobic sludge blanket reactor was studied. The reactor employed had a useful capacity of 9l, operating at mesophilic temperature. Start-up of the reactor was carried out in different steps, beginning with diluted sludge and progressively increasing the amount of sludge fed into the reactor. The study was carried out over a period of 7 months. Different amounts of methanol were added to the feed, ranging between 6.75 and 1cm(3)dm(-3) of feed in order to favour the growth of methanogenic flora. The achieved biodegradation of the sludge using an upflow anaerobic sludge blanket Reactor was very high for an HRT of 9 days, obtaining decreases in COD of 84-87% by the end of the process. Purging of the digested sludge represented approximately 16% of the volume of the treated sludge.     

用味精生产废水培养好氧颗粒污泥

以厌氧颗粒污泥为接种污泥，采用味精生产废水进行培养，在SBR中以逐渐降低污泥沉淀时间的方法成功培养出好氧颗粒污泥。实验结果表明：污泥接种65 d后，出现细小的好氧颗粒污泥，呈黄褐色，95 d后颗粒污泥趋于成熟，粒径达0.6 mm左右，且周围存在大量原生动物；运行95 d后MLSS提高至8.00 g/L，SVI降至30.00 mL/g左右；成熟后的好氧颗粒污泥对味精生产废水中的COD和NH₃-N具有良好的去除效果，出水COD和ρ（NH₃-N）分别为80 mg/L和2 mg/L左右。     

罐底油泥特性分析及其除油处理工艺

通过研究罐底油泥的理化性质,开发了适于处理罐底油泥的系列工艺:先采用调质技术提高罐底油泥流动性;再采用超声破乳降低油泥稳定性,改善油泥分离性能;最后采用卧式离心机对油泥进行离心分离处理.在复合型清洗剂加入量为800 mg/L、超声温度为60℃、超声功率为12 kW、超声时间为25 min、离心温度为60℃、絮凝剂加入量为600 mg/L、离心机转速为2200 r/min的条件下,系统稳定运行9d,离心机出口泥中含油率低于2.00％,水中悬浮固体质量浓度低于170 mg/L,达到了对罐底油泥进行除油的目的.