Persistent organic pollutant emissions from medical waste incinerators in China

The huge amount of medical waste (MW) has caused a tough challenge to environmental protection in China because of its serious infectious potential. At present, incineration is the most common technology for MW disposal. Unfortunately, the medical waste incinerator (MWI) is considered one of the major sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). This study was conducted to investigate the generation and the components of MW; the fingerprint of PCDD/Fs in MWI; and PCDD/F, polychlorinated biphenyl (PCB) and hexachlorobenzene concentrations in residue ash. The estimated annual production of MW was estimated to be 0.97 million tons in China in 2008; in addition, plastic and rubber accounted for 24.5% of MW contents. PCDD/F emissions from MWI could be divided into two main groups according their fingerprints, and the ratio of PCDFs/PCDDs was mostly over 1.5, with a mean value of 3.43. The toxic equivalent of PCDD/Fs was over 30 times that of the value of PCBs in the residue ash, and PCDD/F contents in fly ash accounted for approximately 67% of the total output of PCDD/Fs, which was in line with the UNEP default emission factors for MWI (class 3, 63.7%).     

Identification of surfactants emerged in aerobic granulation

In this study, aerobic granules were cultivated in sequencing batch reactors with activated sludge as the seed. The reactors were operated for 12 h per cycle with the organic loading rate (OLR) increasing in double stepwise from 0.5 to 4.0 g COD L⁻¹ d⁻¹. Within the 40 d running, black granules with regular and smooth morphology were cultivated, which had high wet density and high settling velocity. During the granulation process, foams emerged and disappeared in the reactor, coinciding with the proliferation of filamentous microorganisms in the granules, implying that surfactants might exist and play an important role in the granulation. Using ultra performance liquid chromatography-tandem mass spectrometry, the surfactants were identified as homologous compounds of polyethylene glycol (PEG) with molecular weights ranging mainly from 100 to 500 Da. Their general formulas were proposed as HO-[CH₂-CH₂-O]_n-H. The source of PEG still needs further investigation.     

Thermal removal of PCDD/Fs from medical waste incineration fly ash--effect of temperature and nitrogen flow rate

The fly ash used in this study was collected from a bag filter in a medical waste rotary kiln incineration system, using lime and activated carbon injection followed by their collection as mixed fly ash. Experiments were conducted on fly ash in a quartz tube, heated in a laboratory-scale horizontal tube furnace, in order to study the effect of temperature and nitrogen flow rate on the removal of PCDD/Fs. Results indicated that in this study PCDD/Fs in the fly ash mostly were removed and desorbed very little into the flue gas under thermal treatment especially when the heating temperature was higher than 350 °C, and dechlorination and destruction reactions took important part in the removal of PCDD/Fs. However, in terms of flow rate, when flow rate was higher than 4 cm s⁻¹, destruction efficiency of PCDD/Fs decreased dramatically and the main contributors were P₅CDF, H₆CDF and H₇CDF desorbed to flue gas, the PCDD/Fs in the fly ash decreased with enhanced flow rate.     

气相色谱法测定黄磷生产尾气中的CO_2

针对黄磷生产尾气具有强化学活性和腐蚀性的特点,选择了TDX-01型碳分子筛色谱柱,采用气相色谱法测定黄磷尾气中的CO2。实验结果表明:黄磷尾气中高浓度的CO2用TCD检测器检测,CO2体积分数在0.1%~10%时,检测下限可达到0.05%,方法的平均回收率为93.6%~104.1%,相对标准偏差为2.1%~3.2%;净化后黄磷尾气中的微量CO2经Ni催化甲烷化转化后用FID检测器测定,CO2体积分数在1.0×10-7~1.0×10-4时,方法的检测下限可达到5.0×10-8,相对标准偏差为1.63%。     

采用浅水盘加湿方式实现低温高湿应力

目前运用最为广范的加湿方法是利用浅水盘加湿,根据其加湿原理分析,浅水盘加湿方法一般只能控制在常温以上的湿度。本文介绍一种方法,结合湿度原理在不对设备进行改造的情况下实现了低温高湿的试验应力。同时,反应出国外某些先进设备对试验风险的完善考虑。     

改性粉煤灰净化含磷废水的研究

采用改性粉煤灰对含磷废水进行净化,考察了pH、吸附剂用量、吸附时间和吸附温度对净化效果的影响。结果表明:(1)当pH为9时,磷净化率达到最大值。(2)当改性粉煤灰用量为30g/L时,磷净化率可达99.53%,磷净化后质量浓度为0.91mg/L,达到《污水综合排放标准》(GB8978—1996)中二级标准限值(1.0mg/L);当改性粉煤灰用量为40g/L时,磷净化率可达99.75%,磷净化后质量浓度为0.48mg/L,达到GB8978—1996中一级标准限值(0.5mg/L)。(3)改性粉煤灰对废水中磷的净化速度较快,吸附5min即可使吸附过程达到平衡;进一步提高吸附时间,磷净化率及净化后浓度几乎不再变化。(4)吸附温度对磷净化率的影响较小,当吸附温度为20～40℃时,磷净化率为97.00%～98.62%。(5)改性粉煤灰对磷的吸附等温线较符合Freundlich方程,且1/n=0.374,吸附过程易进行,改性粉煤灰可作为磷的吸附剂用于废水中磷的净化。     

催化臭氧化降解技术中的两个问题

探讨了有机物特性及中间产物H₂O₂在催化臭氧化中的作用。结果表明,有机物在自由基链反应过程中的特性直接影响催化臭氧化的降解效率。当目标有机物是对链反应具有促进作用的甲酸时,自由基引发反应可以明显提高甲酸的臭氧化效率。当目标有机物是对自由基链反应具有抑制剂作用的乙酸时,O₃和Fe²⁺/O₃对乙酸有着相似的降解效率。以上结果表明,自由基引发反应并不是臭氧化降解效率提高的充分条件。另外,当臭氧化过程有H₂O₂产生时,必须考虑类Fenton反应对臭氧化效率的影响。     

Zn/Fe体系湿法催化氧化高效脱除沼气中H2S的研究

提出了Zn/Fe体系湿法催化氧化脱除沼气中H₂S新工艺,阐述了反应机理、实验装置和工艺流程,考察了各单因素操作条件对H₂S脱除效率的影响,在此基础上进行的综合条件实验,脱硫效率都维持在99.6%以上,净化后沼气中H₂S含量低于国家标准。过程不消耗任何化工原料,不产生二次污染,体系无降解问题。     

从稠油罐底泥中回收矿物油

为了回收稠油罐底泥（简称油泥）中的矿物油并提高油泥焚烧系统的处理能力,分析了辽河油泥的特点,对比传统油泥处理方法的优劣,提出了溶剂萃取-离心分离-稠油热废水洗涤-离心分离技术回收矿物油的工艺路线。实验结果表明：该工艺可回收92．07％的矿物油和56．85％的热能;残渣中矿物油的质量分数小于等于2．00％,热值大于等于5000kJ／kg,不需添加辅助燃料即可焚烧处理。     

阳离子交换树脂生产中废酸的回收利用及树脂质量控制

采用 酸套洗工艺代替传统的加水稀释洗涤工艺，成功地解决了阳离子交换树脂生产中废酸的回收利用问题，研究了采用新洗涤工艺后树脂变红的机理和防止对策，结果表明，树脂发红帅微生物的参与而引起的。采以完善洗涤 灭菌措施可防止树脂 ，从而确保了稀酸套洗工艺的顺利实施。