Assessment of Cadmium and Lead in Dried Sewage Sludge from Lubigi Feacal Sludge and Wastewater Treatment Plant in Uganda

Sludge contains organic and inorganic compounds including traces of heavy metals such as lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), chromium (Cr) and others. These metals restrict the use of sludge in agriculture because their accumulation is harmful to the environment and particularly the food chain. Cadmium and lead are among the most common heavy metals found in municipal wastewater treatment plant sludge. They are capable of bioaccumulation in plant tissues like roots and leaves and are non-biodegradable and therefore they remain in the sludge which is disposed on land or used as fertilizers on farms. The presence of heavy metal pollutants serves as a great threat to soils and also makes plants grown on such soils unfit for animal and human consumption as they may have detrimental effects to animal and human life. For instance, Pb and Cd are known to be human carcinogens. This study therefore aimed to investigate the levels of Cd and Pb in the treated dry sludge from Lubigi Feacal Sludge and Wastewater treatment plant located in Kawempe division, Kampala city, Uganda so as to ascertain its safety for use on agricultural lands. Two batches of samples were collected and analyzed at Government Analytical laboratory in Wandegeya, Uganda. The acid digested sludge samples were analyzed using Atomic Absorption Spectroscopy (AAS) method. The average concentrations of Pb found in collected sludge samples, batch 1 (11.912 mg/kg dm) and batch 2 (5.304 mg/kg dm) were far below the Environment Protection Agency (EPA) maximum permissible concentration (840 mg/kg) for any land application. Cadmium was not detected in all the sludge samples collected;there is an implication that it is either completely absent in the sludge generated by the plant or present but far below detectable levels. The sludge generated from Lubigi fecal sludge and wastewater treatment plant is therefore safe for application on agricultural lands as far as Pb and Cd concentrations are concerned.

Removing cadmium from electroplating wastewater by waste saccharomyces cerevisiae

The appropriate condition and scheme of removing cadmium from electroplating wastewater were investigated by adsorption-precipitation method using waste saccharomyces cerevisiae(WSC) as sorbent. Effect factors on biosorption of cadmium in cadmium-containing electroplating wastewater by waste saccharomyces cerevisiae and precipitation process of waste saccharomyces cerevisiae after adsorbing cadmium were studied. The results show that removal rate of cadmium is over 88% after 30 min adsorbing under the condition of cadmium concentration 26 mg/L, the dosage of waste saccharomyces cerevisiae 16.25 g/L, temperature 18 ℃, pH 6.0 and precipitation time 4 h. Biosorption-precipitation method is effective to remove cadmium in cadmium-containing electroplating wastewater by waste saccharomyces cerevisiae. The SEM, infrared spectroscopy and Zeta-potential of the cells show that chemical chelating is the main adsorption form; electrostatic attraction, hydrogen bonding and van der Waals force all function in adsorption process; and ―NH2―,―C=O―,―C=O―NH―,―CH3, ―OH are the main adsorption groups.

Modeling Date Palm Trunk Fibers (DPTF) Packed Bed Adsorption Performances for Cadmium Removal from Aqueous Wastewater

In this study,the potential of a low-cost bio-adsorbent,taken directly from Date Palm Trunk Fibers(DPTF)agricultural wastes,for cadmium ions removal from wastewaters is examined.The performances of this adsorbent are evaluated by building breakthrough curves at different bed heights and flow rates while keeping other parameters,such as the initial feed concentration,pH,and particle size,constant.The results indicate that the maximum cadmium adsorption capacity of DTPF can be obtained from the Thomas model as 51.5 mg/g with the most extended mass transfer zone of 83 min at the lowest flow rate at 5 ml/min.The saturation concentrations(NO)and the rate constant(kab)obtained from the BDST(bed depth service time)model are 7022.16 mg/l and 0.0536 l/mg.min,respectively.Using the Yon-Nelsen Model,it is found that operating at a lower flow rate leads to a larger value of the elapsed needed time to reach a 50%breakthrough.The Wolborska model indicates that the bed capacity increases with decreasing the flow rate,and the adsorbent can achieve a greater external mass transfer kinetic coefficient(2.271/min)at a higher flow rate.

Study on Cadmium Resistant-Bacteria Isolated from Hospital Wastewaters

In hospital, a variety of substances are in use for medical purposes as diagnostics and researches. Among them, heavy metals which are not biodegradable by chemical reactions have bioaccumulation properties. Cadmium is a toxic pollutant that enters hospital wastewaters by different ways. However, isolated bacteria from hospital effluents have high resistance to antimicrobial agents and therefore the ability to uptake cadmium and other metals. So, their use is recommended for wastewater bioremediation. In this study, twelve cadmium-resistant bacteria were isolated from hospital wastewaters and identified. The cadmium-resistant isolates characterized include both Gram-negative [75%] and Gram-positive [25%]. The Minimum Inhibitory Concentration of hospital wastewaters isolates was determined in solid media and was ranged from 250 to 950 micrograms/milliliters. All the isolates showed co-resistance to zinc and mercury. They were also antibiotic resistant and tolerated up a significant concentration of NaCl. The cadmium-resistant species Klebsiella pneumoniae and Pseudomonas aeruginosa were the most resistant to cadmium. The species Klebsiella pneumonia also resists to the highest concentrations of zinc and mercury. The results of toxicity tests on Vibrio fischeri, showed that the DI50 [15 min] as low as 0.07 carried away 50% luminescence inhibition.

Removal of Some Toxic Ions from Seawater and Wastewater by Sorption onto Natural, Synthetic Hydroxyapatite and Alginate-Hydroxyapatite Composite Nanoparticles: A Comparative Study

The main objective of this paper is to study the removal of Cadmium(II), Lead(II), Chromium(VI), and Mercury(II) ions by sorption onto different natural and synthetic nanoparticles. Special attention has been given to the application of fish bone in nanoform as a useful, inexpensive and eco-friendly alternative material. A comparison between natural hydroxyapatite (fish bone), synthetic hydroxyapatite nanoparticles (HAP) and alginate-hydroxyapatite composite (Alg/Hap) to assess their removal efficiencies to remediate the selected heavy metals has been done. Surface characterization by using different techniques has also been performed to understand the influence of surface characteristics of the adsorbent materials in the removal process. Different parameters (pH, contact time, mass dose and metal ion concentration) have been examined to identify the optimum conditions for remediation of different metals from polluted water. The potential applications of the biosorbents for removal and sorption of these metal ions from seawater and wastewater samples were also investigated and evaluated.

Synthesis of Modified Walnut Shell Biochar and Its Performance of Cadmium Adsorption

Biochar is a functional and environmentally friendly material mainly made from by-products of industrial and agricultural production as raw material, which is cracked at high temperatures and slow speeds. The preparation of biochar requires the thermochemical conversion of biomass in an oxygen-restricted environment. Different raw materials and preparation processes result in biochar with different internal structures and biofunctional groups, which often have different properties. Adsorption of heavy metal pollutants is one of the main research directions for biochar application, and there are still areas that can be improved in the current research for biochar for treating heavy metal wastewater. In this study, we take the treatment of cadmium-containing wastewater as an example, walnut shell biochar (WSBC) as a carrier, iron(VI) compounds as a modifying reagent, and test the performance of cadmium-containing wastewater treatment using simulated cadmium-containing wastewater by adjusting the pyrolysis process and modification method at the same time to find the optimal experimental scheme, and give a reasonable theoretical explanation in relation to the results of the characterization tests, such as SEM, FT-IR, and so on. The characterized results show that iron(VI) compound (K2FeO4)-modified WSBC has a significant ability to remove cadmium contamination in the wastewater (remove 96.62% of cadmium in 1 minute), and its structure is different from other iron compound-modified ones. The aim of this study is to improve the efficiency of cadmium adsorption by specific types of biochar, while realizing the whole process as environmentally friendly as possible.

镉离子对养殖废水生物脱氮性能及功能基因的影响

选取了养殖废水中的重金属污染物镉离子为研究对象,为揭示其对生物脱氮系统的影响。检测氮转化功能基因丰度,确定功能基因与理化参数相关性并分析镉离子胁迫下生物脱氮的驱动因素。实验结果表明,镉离子显著抑制生物脱氮性能,硝化过程对于镉离子的敏感性相比于氨氧化过程更强。细菌16S rRNA和氮转化功能基因的丰度随镉离子浓度的升高而显著降低,其中出水氨氮、好氧末端硝酸盐氮浓度都与功能基因呈较强的相关性。此外,硝化和氨氧化水平、NO_(2)^(-)-N的氧化能力、完全反硝化水平是生物脱氮性能的关键驱动因素,分别对氨氮去除率、亚硝酸盐氮积累率、反硝化阶段硝酸盐氮去除率有显著影响。本研究从分子生物学角度揭示镉离子对于生物脱氮的影响,为金属离子对于生物脱氮系统的影响研究提供了理论依据。

花生壳复合水凝胶的制备及其吸附铅、镉性能

以花生壳(PS)、丙烯酸(AA)为聚合单体,过硫酸钾(APS)为引发剂,N,N-亚甲基双丙烯酰胺(MBA)为交联剂,β-环糊精(β-CD)作为增强材料,通过自由基聚合反应合成花生壳木质纤维素/β-环糊精/丙烯酸复合水凝胶[PS(H)/β-CD/PAA];研究了PS(H)/β-CD/PAA的表面性质和微观形貌,考察了在不同环境因子条件下PS(H)/β-CD/PAA对Cd^(2+)、Pb^(2+)的吸附行为和吸附机理。结果表明:PS(H)/β-CD/PAA具有多孔网络结构,加入β-CD后制备的复合水凝胶有更好的机械性能;PS(H)/β-CD/PAA合成成本低,并且可以循环使用;PS(H)/β-CD/PAA对Cd^(2+)、Pb^(2+)可在60 min内达到吸附平衡,最大吸附容量分别为115.67、181.71mg/g,在pH为3~8的较宽范围有良好的效果;PS(H)/β-CD/PAA对Cd^(2+)、Pb^(2+)的吸附过程主要通过离子交换、络合作用或配位作用来进行;此外,PS(H)/β-CD/PAA在处理实际废水时,对Pb^(2+)、Cd^(2+)、Cu^(2+)、Zn^(2+)的去除率分别达76.4%、88.6%、72.9%、31.6%。PS(H)/β-CD/PAA处理水体重金属效果良好,能够充分利用资源、节约成本,可作为一种重金属废水处理的潜在新材料。

市政污泥陶粒对Cd^(2+)吸附特性的影响

为拓展市政污泥资源化利用和无害化处理途径,本研究以市政污泥、黏土和膨润土为原料,采用高温烧结技术制备市政污泥陶粒,以含Cd^(2+)废水为污染物,考察市政污泥陶粒添加量、溶液初始pH值、吸附时长及Cd^(2+)初始浓度对陶粒吸附性能的影响,研究其吸附动力学与等温吸附特性,并借助X射线衍射(XRD)、扫描电子显微镜(SEM)等表征手段,揭示其吸附机理。结果表明:①烧结后,市政污泥陶粒表面粗糙、孔隙结构及官能团丰富;②石英(SiO_(2))、莫来石(Al_(6)Si_(2)O_(13))、钙长石(CaAl_(2)Si_(2)O_(8))和赤铁矿(Fe_(2)O_(3))是市政污泥陶粒的主要晶相,吸附Cd^(2+)后矿物成分不变;③在特定条件(陶粒添加量50 g、Cd^(2+)初始浓度300 mg/L、吸附时间120 min、pH值6)下,Cd^(2+)去除率高,表明陶粒具备高效吸附Cd^(2+)的能力;④市政污泥陶粒对Cd^(2+)的吸附包含物理吸附和化学吸附两种吸附方式,相较于准二级动力学模型,更符合准一级动力学模型,市政污泥陶粒对Cd^(2+)的吸附既存在单层吸附,又存在多层吸附,吸附机制较复杂。研究结果可为市政污泥的资源化利用以及对Cd^(2+)污染物的处理提供科学依据和技术支持。

某石煤矿含镉酸性废水处理站改造工程实例

由于环保政策的影响,益阳地区许多小型煤矿已经关闭,但它们矿区周围仍有渗漏的水需要持续处理。本项目在早期阶段由于雨水和含镉废水分流不彻底,处理规模与实际的废水排放量存在较大差异,处理流程不尽完善,废水水质的监测和自动控制相对不足,出水水质稳定性存在问题。此外,污泥处理技术相对落后,实际处理能力不足。针对上述问题,我们对雨水和污水处理分流进行了优化,增加了调节池,采用了新型含镉酸性废水一体化处理设备,选择了更经济的药剂,提升了控制系统的自动化水平,并对污泥处理系统进行了改进,实现运行效果的提升及运行成本的降低。

氢氧化镁处理含镉废水的研究

以氢氧化镁作为吸附剂处理含镉酸性废水 .结果表明 ,氢氧化镁对Cd2 +的吸附为化学吸附 ,去除率一般可达 98%以上 .氢氧化镁回收后 ,经轻烧处理变成氧化镁 ,仍可以处理含镉废水 。

含氰废水处理方法

综述了含氰废水及其处理方法。重点介绍了处理含氰废水方法—氧化法、酸化回收法、化学沉降法和微生物降解法、自然降解法、碱氯氧化法、双氧水氧化法、高温水解法、电解法、二氧化碳—空气氧化法及纳米二氧化钛光催化氧化法的基本原理。

镉在不同土壤和蔬菜中残留规律研究

研究了镉在不同类型土壤和蔬菜中的残留积累规律.结果表明,含镉污水灌溉是造成农田土壤镉污染主要原因之一.土壤中镉残留量随污水镉浓度增加而增高.土壤镉含量与蔬菜中镉含量呈显著正相关.供试土壤及蔬菜可食部分镉的累积顺序为:粘土>壤土;壤土蔬菜>粘土蔬菜,小白菜(叶)>萝卜(根)>莴苣(茎)>辣椒(果)>豇豆(豆).

生物吸附-沉降法去除电镀废水中镉

以水洗废啤酒酵母为吸附剂,采用吸附-沉降法,研究水洗废啤酒酵母对电镀废水中镉的吸附规律及沉降效果。结果表明,在废水中镉含量为26mg/L、pH7、水洗废啤酒酵母用量40g/L(含水约72%)、室温(约18℃)、搅拌速度800r/min、吸附时间30min、沉降3.5h的条件下,废水中镉的吸附率及吸附-沉降后镉的去除率均达96%以上。并采用透射电子显微镜、电动电位及红外光谱分析手段,分析水洗废啤酒酵母对镉的吸附机理。水洗废啤酒酵母对镉的吸附不仅发生菌体表面,也发生在菌体内部。吸附过程存在化学络合、静电吸引、氢键等作用。

脉冲电絮凝处理含镉重金属废水

采用脉冲电絮凝方法处理含镉重金属废水,考察了通电时间、pH值、离子强度、电流密度及占空比等因素对溶液中Cd2+去除效果的影响,并结合相应的计算公式核算了相应的电耗和铝板消耗。实验结果表明,在通电时间为60 min,电流密度为10 mA/cm2,电导率为7.8 ms/cm,占空比2.5,pH值7.82的条件下,Cd2+去除率达到了99.86%,电耗和铝板消耗分别为0.832 kWh/m3和100.7 g/m3。

ClO_2对医院高浓度含氰废水处理的试验研究

以医院排放的高浓度含氰废水为研究对象 ,采用“硫酸亚铁 +曝气”初级化学处理和ClO2 二级深度氧化处理相结合的处理模式 ,不仅使含氰废水实现无毒化处理 ,而且使高浓度含氰废水实现资源化回收利用。试验表明 ,处理后的废水中CN-浓度达到国家排放标准GB8978 1996中的一级标准 ,为医院高浓度含氰废水的治理提供了一种新的方法。

壳聚糖活性污泥复合吸附剂处理铅、镉废水研究

研究了壳聚糖活性污泥复合吸附剂(SCTS)对废水中Pb^(2+)和Cd^(2+)的吸附性能,通过单因素试验分析了温度、SCTS投加量、pH值、搅拌转速和重金属离子浓度对SCTS吸附性能的影响,正交试验确定了影响因素的主次顺序及最优组合水平。结果表明:影响SCTS吸附废水中Pb^(2+)的因素从大到小依次为pH值、SCTS投加量、Pb^(2+)初始浓度和搅拌转速,吸附Pb^(2+)的最优组合为pH值=2、SCTS投加量为10 g· L^(-1)、ρ(Pb^(2+))初始值为50 mg· L^(-1)、搅拌转速130 r·min-1,Pb^(2+)去除率达95.76%。影响SCTS吸附废水中Cd^(2+)的因素作用力大小依次为pH值、Cd^(2+)初始浓度、转速和SCTS投加量,吸附Cd^(2+)的最优组合为pH值2、SCTS投加量2.5 g· L^(-1)、ρ(Cd^(2+))初始值60 mg· L^(-1)、转速130 r·min-1,此时Cd^(2+)的去除率为96.08%。

啤酒酵母吸附镉离子的试验研究

研究了啤酒酵母对镉的生物吸附过程 ,结果表明 ,啤酒酵母吸附镉的速度是非常快的 ;p H对镉的吸附影响较大 ,吸附较佳的 p H范围为 4～ 8,并且啤酒酵母有调节 p H的作用 ,p H为 4～ 8的溶液在吸附反应后 ,其 p H接近于 5 .8;温度、酵母用量、Cd2 +的初始浓度对吸附均有一定的影响。实际含镉废水处理结果表明 ,啤酒酵母处理含镉废水是有效的。

改性淀粉在低浓度含镉废水处理中的应用实验

Graft copolymerization of acrylamide onto starch and reaction with mercaptoacetic acid subsequently were studied.The reaction product(St-AM-MCAA) was used in the treatment of wastewater containing low concentration cadmium ion(0.40 mg·L-1) as additive.An investigation was carried out to study the effect of St/AM(mass ratio of starch to acrylamide) on the grafting ratio and grafting efficiency and the content of thiol(SH) group.It was found that the cadmium ion removal percentage by St-AM-MCAA3 reached 89.7% and the residual concentration of cadmium ion in treated water was under 0.10 mg·L-1 in the conditions of pH=8 and additive concentration of 2.0 g·L-1 by selecting a high grafting ratio and thiol content product St-AM-MCAA3 as additive.The ability of St-AM-MCAA3 to remove low concentration wastewater containing cadmium ion was higher than that of St-AM3 by 10%.

武钢焦化公司酚氰废水治理现状及改进措施

本文介绍了武钢焦化公司酚氰废水的来源、治理的原理、工艺流程及运行现状 ,并对一些环节提出了具体的改进措施和建议。