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随着我国水处理需求及能力的大幅度提升,剩余污泥的产量也逐渐增大。据预测,2020—2025年间,剩余污泥的年产量将突破6×107 t (以含水率80%计)[1]。相比污水的处理,我国的污泥处理能力相对滞后[2]。由于污泥中含有大量的重金属和有毒有害物质[3],80%以上的污泥由于处理不当,已成为造成环境二次污染的污染源[4]。因此,污泥的妥善处理处置已成为亟需解决的环境问题之一。
剩余污泥中的有机物主要包括蛋白质和多糖[5]。其中,蛋白质含量为20%~40%,是一种有机质资源,通过污泥蛋白质回收实现其资源化,是剩余污泥处理处置的重要途径之一[6]。剩余污泥中的蛋白质主要存在于微生物细胞内,通过水解破胞技术将微生物细胞内蛋白质释放到溶液中,是污泥蛋白质回收的前提[7]。目前,水解破胞技术主要包括物理法、化学法和生物法。XIAO等[8]采用热处理溶出污泥蛋白质,可使溶液中的蛋白质浓度提高12倍。肖本益等[9]采用碱法处理活性污泥,10 g·L−1的污泥在pH 12.0的条件下,处理12 h后,溶解性蛋白质浓度增加了2 058.6 mg·L−1。章文锋等[10]采用酶法回收污泥蛋白质,发现碱性蛋白酶在pH 8、温度55 ℃、酶投加量2%、反应时间4 h及污泥液固比4∶1条件下,污泥蛋白提取率可达52.5%。ASSAWAMONGKHOLSIRI等[11]采用热酸法溶出蛋白质,在pH为1.0的条件下,预处理6 h,然后在110 ℃下加热60 min,可溶性蛋白质浓度提高了4.8倍。CHO等[12]发现,在60 ℃和pH 12的条件下处理1 h,污泥释放的蛋白质是未预处理污泥的2.4倍,而单独碱解释放的蛋白质是未预处理污泥的2.1倍。LIU等[13]用超声联合碱处理的方法溶出污泥蛋白,在18 kHz和pH 12下处理1 h,蛋白质浓度增加到7.9 g·L−1。SAHINKAYA[14]采用超声联合酸处理的方法分解污泥,在超声功率密度为1 W·mL−1、处理时间为10 min、初始污泥pH为2.0的最佳条件下,蛋白质浓度可达1 750 mg·L−1。然而,目前污泥联合水解工艺多处于实验室研究阶段,其中试及产业化效果则有待考证。
为此,本研究建立了日处理规模为1 m3剩余污泥(含水率为80%)的中试水解系统。采用酶联合热碱水解技术,优化了影响蛋白质溶出效果的关键工艺条件,包括酶解时间、酶投加量及碱解时间等;同时,进一步研究了污泥水解的动力学特性,解析了联合水解过程的限速步骤,以期为剩余污泥联合水解工艺的产业化应用提供必要的技术参数。
基于污泥蛋白质溶出的酶-热碱联合水解中试研究
Pilot-scale study on enzymatic-thermo-alkaline joint hydrolysis based on sludge protein dissolution
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摘要: 为探究剩余污泥酶-热碱联合水解生产蛋白质工艺工业化利用的可能性,建立了1 m3·d−1的剩余污泥(含水率80%)的中试水解系统。通过对酶解时间、复合添加量及碱解温度等关键工艺因素优化,获得了中试规模污泥联合水解的最佳工艺条件;通过酶和热碱水解动力学研究,明确了联合水解过程的限速步骤。结果表明:在日处理量为1 m3剩余污泥(含水80%)的中试水解过程中,酶解时间为1.5 h、复合酶投加量为1%、污泥浓度为30 g·L−1、碱解时间1.5 h、碱解温度80 ℃时,蛋白质溶出效果最佳,上清液中蛋白质浓度为2 160 mg·L−1;污泥酶解过程符合米氏方程,碱解过程符合零级动力学方程,二者的水解速率分别为0.709 mg·(L·min)−1和11.046 mg·(L·min)−1;与碱解相比,酶解是剩余污泥联合水解的限速步骤。研究结果可为污泥联合水解工艺产蛋白质的产业化应用提供必要的技术参数。Abstract: In order to explore the possibility of industrial utilization of the enzymatic-thermo-alkali joint hydrolysis process of excess sludge to produce protein, a pilot-scale hydrolysis system of 1 m3·d−1 excess sludge (moisture content 80%) was established. The optimal conditions of the pilot-scale enzymatic-thermo-alkali joint hydrolysis were achieved by optimizing key technological factors, such as enzymatic hydrolysis time, compound enzyme dosage and alkali hydrolysis temperature, etc. Then, the rate-limiting step of the joint hydrolysis process was determined by studying the kinetics of enzymatic and alkali hydrolysis. The results showed that during the pilot-scale hydrolysis process of 1 m3 excess sludge (80% water content) per day, the best protein dissolution effect was achieved and the protein concentration in supernatant was 2 160 mg·L−1 at enzymatic hydrolysis time of 1.5 h, compound enzyme dosage of 1%, sludge concentration of 30 g·L−1, alkali hydrolysis time of 1.5 h and alkali hydrolysis temperature of 80 ℃. The sludge enzymatic process followed Michaelis equation with hydrolysis rate of 0.709 mg·(L·min)−1, and the thermo-alkali hydrolysis process followed zero order dynamic equation with hydrolysis rate of 11.046 mg·(L·min)−1. The rate-limiting step of the joint hydrolysis process was enzymatic hydrolysis compared to the thermo-alkali hydrolysis. The research results can provide necessary technological parameters for the industrial application of the sludge joint hydrolysis process to produce protein.
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Key words:
- sludge hydrolysis /
- protein recovery /
- enzymatic-thermo-alkali joint hydrolysis /
- dynamic
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表 1 参数及动力学方程
Table 1. Parameters and dynamic equations
酶投加量/% $ {K}_{\mathrm{m}} $ /(mg·L−1)$ {v}_{\mathrm{m}\mathrm{a}\mathrm{x}} $ /(mg·(L·min)−1)R2 显著性(α<0.05) 反应动力学方程 1 13.13 0.709 0.997 0.001 $ v=\dfrac{0.709{C}_{\mathrm{S}}}{13.13+{C}_{\mathrm{S}}} $ 2 7.77 0.659 0.985 0.001 $ v=\dfrac{0.659{C}_{\mathrm{S}}}{7.77+{C}_{\mathrm{S}}} $ 3 5.36 0.611 0.986 0.001 $ v=\dfrac{0.611{C}_{\mathrm{S}}}{5.36+{C}_{\mathrm{S}}} $ -
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