强化化学淋滤对污泥重金属溶出及磷释放的影响

针对采用传统化学淋滤方法处理污水污泥时重金属溶出率低的问题,设计了两种强化化学淋滤方法的对比试验,通过检测重金属形态分布、污泥有机质及磷释放、污泥含固率,研究了强化化学淋滤对污泥各方面综合性能的影响。结果表明:稀硫酸与氯化铁联合处理(处理方法1)对Cu和Cr的溶出效果不明显,但在加入NaNO₂(处理方法2)后使Cu溶出率由7%提升至82%,Zn溶出率由79%提升至88%;同时,两种强化化学淋滤方法均增加了污泥中有机质和磷的释放,污泥中磷含量由23.2 mg/g分别降至12.3 mg/g和10.7 mg/g;与原污泥相比,强化淋滤后的污泥脱水性也均得到了明显改善,其污泥含固率分别提高了52%和61%。     

污泥焚烧工程中的磷形态分布与磷迁移研究

以竹园污泥焚烧工程为依托,采用SMT方法研究磷在干污泥、炉渣和飞灰中的含量及赋存形态。结果表明,焚烧过程使炉渣及飞灰中的总磷(TP)含量比干污泥提高了2~3倍,还使其中的无机磷(IP)含量大幅提升至TP总量的99%以上,在实现磷富集的同时有效提升了磷的生物可利用性。分析焚烧过程对磷灰石无机磷(AP)和非磷灰石无机磷(NAIP)的影响,发现镁离子与钙离子会与污泥中的NAIP发生反应,取代铝离子从而生成钙镁结合形式的AP;与炉渣相比,飞灰在布袋处受CaO添加的影响,此种转化趋势更为明显,AP已经超过NAIP成为优势形态,占IP总量的78.4%。焚烧是上海地区处理污泥的主要方式,该研究结果从营养物回收角度为污泥焚烧飞灰的资源化利用提供了新思路。     

Elutriated acid fermentation of municipal primary sludge

The performance of a novel fermentation process, adopting a sludge blanket type configuration, for higher hydrolysis/acidogenesis of the municipal primary sludge was investigated under batch and semi-continuous conditions with varying pH and temperature. This acid elutriation slurry reactor provided higher system performance with a short HRT (5d) and higher acidogenic effluent quality under pH 9 and thermophilic (55 degrees C) conditions. The hydrolysis of the sludge was revealed to be significantly dependent on seasonal effects for sludge characteristics but with little impact on acidogenesis. Based on the rainy season at the optimal conditions, VFA production and recovery fraction (VFA(COD)/COD) were 0.18 g VFA(COD)/g VSS(COD) and 63%. As byproducts, nitrogen and phosphorus release were measured at 0.006 g N/g VSS(COD) and 0.003 g P/g VSS(COD), respectively. For the mass balance in a full-scale plant (Q=158,880 m(3)/d) based on the rainy season, the VFA and non-VFA (as COD) production were 3110 kg VFA(COD)/d and 1800 kg COD/d, resulting in an increase of organics of 31 mg COD/L and 20mg VFA(COD)/L and nutrients of 0.7 mg N/L and 0.3 mg P/L in the influent sewage. The economical benefit from this process application was estimated to be about 67 dollars per 1000 m(3) of sewage except for energy requirements and also, better benefits can be expected during the dry season. Moreover, the results revealed that the process has various additional advantages such as pathogen-free stabilized solids production, excellent solids control and economical benefits.     

Recovery of nitrogen and phosphorus from alkaline fermentation liquid of waste activated sludge and application of the fermentation liquid to promote biological municipal wastewater treatment

In previous publications we reported that by controlling the pH at 10.0 the accumulation of short-chain fatty acids (SCFA) during waste activated sludge (WAS) fermentation was remarkably improved [Yuan, H., Chen, Y., Zhang, H., Jiang, S., Zhou, Q., Gu, G., 2006. Improved bioproduction of short-chain fatty acids (SCFAs) from excess sludge under alkaline conditions. Environ. Sci. Technol. 40, 2025-2029], but significant ammonium nitrogen (NH₄-N) and soluble ortho-phosphorus (SOP) were released [Chen, Y., Jiang, S., Yuan, H., Zhou, Q., Gu, G., 2007. Hydrolysis and acidification of waste activated sludge at different pHs. Water Res. 41, 683-689]. This paper investigated the simultaneous recovery of NH₄-N and SOP from WAS alkaline fermentation liquid and the application of the fermentation liquid as an additional carbon source for municipal wastewater biological nitrogen and phosphorus removal. The central composite design (CCD) of the response surface methodology (RSM) was employed to optimize and model the simultaneous NH₄-N and SOP recovery from WAS alkaline fermentation liquid. Under the optimum conditions, the predicted and experimental recovery efficiency was respectively 73.4 and 75.7% with NH₄-N, and 82.0 and 83.2% with SOP, which suggested that the developed models described the experiments well. After NH₄-N and SOP recovery, the alkaline fermentation liquid was added to municipal wastewater, and the influence of volume ratio of fermentation liquid to municipal wastewater (FL/MW) on biological nitrogen and phosphorus removal was investigated. The addition of fermentation liquid didn't significantly affect nitrification. Both SOP and total nitrogen (TN) removal were increased with fermentation liquid, but there was no significant increase at FL/MW greater than 1/35. Compared to the blank test, the removal efficiency of SOP and TN at FL/MW = 1/35 was improved from 44.0 to 92.9%, and 63.3 to 83.2%, respectively. The enhancement of phosphorus and nitrogen removal was mainly attributed to the increase of influent SCFA, or rather, the increase of intracellular polyhydroxyalkanoates (PHA) which served as the carbon and energy sources for denitrification and phosphorus uptake. The addition of alkaline fermentation liquid to municipal wastewater, however, increased the effluent COD, which was caused mainly by the increase of influent humic acid, not protein or carbohydrate.     

Acid solubilization of sewage sludge and ash constituents for possible recovery

Many of the trace elements and phosphorus in digested sewage sludges can be solubilized with acid at an average acid cost of $41 and $77 per ton of dry solids for H₂SO₄ and HCl, respectively ($46 and $86/metric ton). But an economic gain accrued by the recovery of metals and phosphates would be minimal since processing of the large volumes of dilute acid leachate would be expensive. Based on acid costs alone, sludge detoxification does not seem to be economically feasible, so the elimination of metal discharges at source seems to be the only practicable solution to reducing heavy metal levels in digested sludges.

Sulfuric acid can be used to non-selectively solubilize metals and phosphates from sludge incinerator ash for about $21 per ton of ash treated ($24/metric ton). In most instances, separation and recovery of the constituents in the leachate would be too costly to make profitable recycle possible. Optimization of incineration parameters such as temperature can be used to minimize the environmental impact of landfilling sludge incinerator ash.     

Wastewater sludge as a potential raw material for antagonistic fungus (Trichoderma sp.): role of pre-treatment and solids concentration

Feasibility of production of antagonistic Trichoderma sp. conidial spores using wastewater sludge as a raw material employing different suspended solids concentration (10-50 g/l) was investigated in shake flasks. Maximum conidial spore count obtained for raw sludge was 1.98 x 10(4) CFU/ml, which was enhanced by sludge pre-treatments (alkaline and thermal alkaline). Conidial spore count ranging from 1.3 x 10(6) to 2.8 x 10(7) CFU/ml was observed for alkaline and thermal alkaline treated sludges. Optimal suspended solids concentration was 30 g/l (10(7) CFU/ml) whereas, lower (<20 g/l) and higher (>30 g/l) solids concentration were less efficient. Thermal alkaline pre-treated sludge showed diauxic growth due to multiplicity of sludge biodegradability. A simple, modified CFU filtration technique was also developed for fungal spore assessment in sludge. Bioassay of fermented sludge against spruce budworm larvae showed entomotoxicity (15036 SBU/microl), on par with Bacillus thuringiensis biopesticides. This study successfully demonstrated potential of wastewater sludge as a raw material for production of value added product, aiding in sludge management and proliferation of eco-friendly and economical biocontrol agents.     

Phosphorus recovery from sewage sludge with a hybrid process of low pressure wet oxidation and nanofiltration

Phosphorus recovery from sewage sludge will become increasingly important within the next decades due to depletion of mineral phosphorus resources. In this work a new process concept was investigated, which aims at realising phosphorus recovery in a synergistic way with the overall sewage sludge treatment scheme. This process combines a low pressure wet oxidation for sewage sludge decomposition as well as phosphorus dissolution and a nanofiltration process to separate phosphorus from heavy metals and obtain a clean diluted phosphoric acid, from which phosphorus can be recovered as clean fertiliser.It was shown that this process concept is feasible for sewage sludge for wastewater treatment plants that apply enhanced biological removal or precipitation with alumina salts for phosphorus removal. The critical parameter for phosphorus dissolution in the low pressure wet oxidation process is the iron concentration, while in the nanofiltration multi-valent cations play a predominant role.In total, a phosphorus recovery of 54% was obtained for an exemplary wastewater treatment plant. Costs of the entire process are in the same range as conventional sewage sludge disposal, with the benefit being phosphorus recovery and reduced emission of greenhouse gases due to avoidance of sludge incineration.     

有机负荷对污泥减量HA-A/A-MCO工艺吸放磷的影响

开发了一种具有同步除磷脱氮和污泥减量功能的HA-A/A-MCO工艺,分析了该工艺的方法及流程,并对其进行了试验研究,通过静态试验发现,当负荷增加至一定程度,有机物不再是磷释放的限制性因子,HA-A/A-MCO系统厌氧释磷的临界有机负荷为0.141 g COD/（g MLSS.d）,单位污泥最大可释放贮磷量为5.7 mg P/g MLSS。     

超声强化污泥释磷及MAP法磷回收优化研究

为提高剩余污泥的磷释放与回收效果,采用超声强化EDTA-厌氧处理后的剩余污泥释磷,并以鸟粪石(MAP)结晶法回收上清液中的磷,探究超声对磷释放的影响,同时确定了最佳超声工作参数,采用响应曲面法构建MAP法磷回收的二次多项式模型并验证了模型的适用性。结果表明,超声可以强化污泥中磷的释放,最佳超声工作参数如下:声能密度为1.0 W/m L、超声时间为40 min,在最佳工作参数下可向液相释放60%的TP,TP、PO34--P浓度分别达到未超声处理的1.6倍和1.4倍;经超声后污泥上清液中TP增加量与MLSS、MLVSS减少量呈正相关关系,每溶解1 mg的MLSS向上清液中释放0.010 1 mg的TP;磷回收的最优工艺条件:nMg/nP=2、pH值=9、搅拌时间为21 min,此时磷回收率为89.29%,回收的晶体产物主要成分是磷酸铵镁,其纯度为77.56%,且相比未超声,该条件下的回收量提高了30%。     

Utilization of treated spent liquor sludge with fly ash in cement and concrete

Design mix of M-20 concrete was prepared in the laboratory by substituting cement with the treated spent liquor sludge (TSLS) and fly ash. During the study, TSLS is fixed at 7.5% by weight, and fly ash is varied as 5%, 10%, 15%, 20% and 25% to study the possibility of replacement of cement. A 15% fly ash gives the optimum compressive strength. Addition of fly ash has resulted in complete removal of toxicity as per US EPA toxicity characteristic leaching procedure (TCLP) test. A total of 7.5% sludge and 15% fly ash in M-20 concrete is expected to save Rs. 252/m³ (≈USD 5.3/m³⁾ of concrete.     

污泥生物淋滤过程中Cd及Pb形态变化研究

对太原市污水处理厂的污泥进行了生物淋滤序批实验研究,采用5％接种量和底物浓度4g/L单质硫为工艺参数,采用顺序浸提法测定了生物沥滤中重金属形态之间的转化,通过淋滤前后重金属形态变化分析了其沥滤机制及浸出能力。结果表明,cd是通过间接机制沥出,Pb的沥出主要是由直接机制和间接机制的共同作用完成的。研究结果对预测污泥农用的环境风险有积极意义。     

Experimental studies simulating potential phosphorus release from municipal sewage sludge deposits

In a laboratory experiment, artificial rainwater was passed through Fe- and Al-precipitated sludge. The release of phosphorus (P) at different temperatures and different oxygen conditions was studied up to 160 d. Under anaerobic conditions and at a temperature of 20°C, 95% of the total P in sludge was released as phosphate. In contrast, in an aerobic environment at the same temperature, only between 20 and 30% of the total phosphorus was released. Water oxygen status and flow size through the sludge were found to be the main factors controlling the P release. Phosphorus fractionations demonstrated that 75% of the total P in sludge initially was found in the NaOH extractable fraction representing P adsorbed to Fe compounds, for example. After passage of oxygenated artificial rainwater, a transformation to more inert P-compounds occurred (HCl extractable and inert P) while only 10% remained in the NaOH extractable fraction. The risk of increasing non-point pollution of P from P-accumulating sludge deposits is discussed.     

Studies on the recovery of sludge protein

The effect of sodium hydroxide and sodium chloride alone as well as in combination on sludge protein solubilization was investigated. Sodium hydroxide treatment was found superior as a maximum protein solubilization (90%) was obtained by its use at pH 12.5. For the extraction of protein hydrochloric acid, sodium lignosulphonate, sulphuric acid, acetic acid and ammonium sulphate, as protein precipitating agents, were also tried. Of all the precipitants used ammonium sulphate (40%) was found most effective giving a maximum protein recovery (91%).Four parameters were mainly studied for the characterization of recovered protein. These include determination of total protein, moisture, ash and heavy metals. It was also found that protein recovery unit processes removed most of the metals originally present in the primary sludge and the recovered product contained all the essential amino acids which could serve as an animal feed supplement.     

Leaching techniques to remove metals and potentially hazardous nutrients from trout farm sludge

A fish farm sludge high in P (2-6% w/w as dry matter), Fe (5-7%), C (40-50%) and N (0.8-4%) was subjected to a series of acid leaching treatments using HCl, organic acids, and biologically mediated acid production. Additions of biodegradable organic acid solubilized heavy metals better than HCl, while additions of 1.5% w/v glucose followed by 7 day incubation stabilized the sludge releasing 92% P, 100% Fe. The use of homo-lactic Lactobacillus plantarum starter cultures were more effective than hetero-lactic Lactobacillus buchneri, solubilizing 81.9% P, 92.2% Fe, 93.0% Zn and 96.4% Ca in the sludge. The anaerobic sludge-glucose fermentation using L. plantarum produced a leached sludge that has low heavy metal and nutrient content while affording the recovery of nutrients. The potential of these methods for practical application are briefly discussed.     

On wet chemical phosphorus recovery from sewage sludge ash by acidic or alkaline leaching and an optimized combination of both

The advantages and drawbacks of existing wet chemical phosphorus (P) recovery technologies, their applicability to different types of sewage sludge ash (SSA) and the role of the decay products of detergent zeolites as a source of reactive Al in SSA are analyzed. Since neither a purely acidic nor a purely alkaline treatment are able to provide satisfactory technical solutions a wet chemical phosphorus (P) recovery process for sewage sludge ashes (SSAs) is investigated in detail that is based on a sequential treatment of SSA with an acid and a base. As a result of an acidic pre-treatment, the P fraction of the raw SSA that was bound as - alkaline-insoluble - calcium phosphate (Ca-P) is converted into aluminum phosphate (Al-P). This newly formed Al-P can be easily dissolved via alkaline treatment and then easily separated from the alkaline leachate via precipitation of Ca-P. The Al-component can be reused as precipitant for P-removal in waste water treatment plants (WWTPs). The investigated process requires fewer chemicals than the direct acidic dissolution of all P-compounds contained in the SSA. This is due to the described rearrangement of the P component from Ca-P to Al-P. That such a rearrangement of P occurs indeed was confirmed through a combination of XRD, ICP and XRF analyses together with mass balance calculations. The present investigation proves that the process works for very different types of SSAs: For Al-rich SSAs that come from WWTPs where Al-salt is used for chemical P-removal the described sequential treatment process works best and yields P-recovery rates as high as 70-77%. But even for SSAs from WWTPs where only iron salt is used for chemical P-removal, a considerable amount of the reactive Al necessary for the described P-rearrangement is supplied by decay products of detergent zeolites, a hidden Al-source present in most SSAs produced in Europe.     

污泥经生物淋滤后氮磷钾的流失

介绍了研究污泥经生物淋滤后N,P,K等营养物质流失情况的材料与方法,阐述了测定污泥中N,P,K含量的方法及原理,对生物淋滤前后污泥中N,P,K的变化作了分析,结果表明：污泥经生物淋滤后N,P,K含量分别为1．53％,0．58％,0．28％,仍能保持较好的肥效。     

生物除磷颗粒污泥与絮状污泥特性的对比研究

以絮状生物除磷污泥为参照,对生物除磷颗粒污泥的物理、化学、生物特性和除磷特性进行系统研究。结果表明:生物除磷颗粒污泥呈淡黄色,外观呈球形或椭球形,边界光滑清晰,沉降速度在15～20 m/h左右,含水率为95.94%,相对密度为1.193,粒径在0.3～0.5 mm之间,SVI值在50 mL/g以下,颗粒污泥最大比释磷速率和最大比吸磷速率分别为104.43、44.72 mgP/(gVSS.h),污泥中总磷含量(TP/SS值)为7.4%;絮状生物除磷污泥呈淡黄色,结构紧密,污泥含水率为97.65%,相对密度为1.040,最大比释磷速率和最大比吸磷速率分别为104.82、42.43 mgP/(gVSS.h),TP/SS值达到9.5%。生物除磷颗粒污泥具有较强的除磷能力和优良的物理、化学、生物性能。     

Waste activated sludge fermentation: Effect of solids retention time and biomass concentration

Laboratory scale, room temperature, semi-continuous reactors were set-up to investigate the effect of solids retention time (SRT, equal to HRT hydraulic retention time) and biomass concentration on generation of volatile fatty acids (VFA) from the non-methanogenic fermentation of waste activated sludge (WAS) originating from an enhanced biological phosphorus removal process. It was found that VFA yields increased with SRT. At the longest SRT (10 d), improved biomass degradation resulted in the highest soluble to total COD ratio and the highest VFA yield from the influent COD (0.14 g VFA-COD/g TCOD). It was also observed that under the same SRT, VFA yields increased when the biomass concentration decreased. At a 10 d SRT the VFA yield increased by 46%, when the biomass concentration decreased from 13 g/L to 4.8 g/L. Relatively high nutrient release was observed during fermentation. The average phosphorus release was 17.3 mg PO₄-P/g TCOD and nitrogen release was 25.8 mg NH₄-N/g TCOD.     

Kinetic competition between phosphorus release and denitrification on sludge under anoxic condition

The kinetic behaviors of simultaneous phosphorus release and denitrification on sludge were investigated under anoxic condition. A phosphorus enriched sludge produced from Anaerobic-Anoxic-Oxic (AnAO) process under various SRT (5, 10 and 15 days) operation conditions was carried out in a series of batch tests. Experimental results indicated that the available organic substrate determined the kinetic behaviors of phosphorus release/uptake and denitrification. The simultaneous phosphorus release and denitrification demonstrated a kinetic competition under anoxic conditions in the presence of an available organic substrate. When the substrate was abundant, sludge was under “releasable-phosphorus-limited” condition; phosphorus release rate decreased slightly by nitrate inhibition. However, nitrate significantly inhibited phosphorus release when sludge was under “initial-substrate-limited” condition. Moreover, the sludge's phosphorus contents (as created by different SRT processes) dominated the kinetics of competition between phosphorus release and denitrification. The sludge with a high phosphorus content had a higher phosphorus release rate in accordance with a lower denitrification rate. Additionally, the substrate sequestrated rate markedly increased under the condition of simultaneous phosphorus release and denitrification. Finally, a preliminary metabolism model of denitrifying phosphorus removal bacteria was proposed, and found to be capable of adequately accounting for simultaneous phosphorus release and denitrification under anoxic conditions.     

Biological short-chain fatty acids (SCFAs) production from waste-activated sludge affected by surfactant

Short-chain fatty acids (SCFAs), the preferred carbon sources for biological nutrient removal, are the important intermediate products in sludge anaerobic fermentation. Sodium dodecylbenzene sulfonate (SDBS) is a widespread used surfactant, which can be easily found in waste-activated sludge (WAS). In this investigation, the effect of SDBS on SCFAs production from WAS was investigated, and the potential of using fermentative SCFAs to promote enhanced biological phosphorus removal (EBPR) was tested. Results showed that the total SCFAs production increased significantly in the presence of SDBS at room temperature. At fermentation time of 6 days, the maximum SCFAs was 2599.1mg chemical oxygen demand (COD)/L in the presence of SDBS 0.02g/g, whereas it was only 339.1mg (COD)/L in the absence of SDBS. The SCFAs produced in the case of SDBS 0.02g/g and fermentation time 6 days consisted of acetic acid (27.1%), propionic acid (22.8%), iso-valeric acid (20.1%), iso-butyric acid (11.9%), n-butyric acid (10.4%) and n-valeric acid (7.7%). It was found that during sludge anaerobic fermentation, the solubilization of sludge particulate organic-carbon and hydrolysis of solubilized substrate as well as acidification of hydrolyzed products were all increased in the presence of SDBS, while the methane formation was decreased, the SCFAs production was therefore remarkably improved. Further investigation showed that the production of SCFAs enhanced by SDBS was caused mainly by biological effects, rather than by chemical effects and SDBS decomposition. With the fermentative SCFAs as the main carbon source, the EBPR maintained high phosphorus removal efficiency ( approximately 97%).