YIC-IR
微藻对高硫酸盐及重金属模拟废水的处理与机理研究
周浩媛
Subtype博士
Thesis Advisor盛彦清
2019
Degree Grantor周浩媛
Place of Conferral中国科学院大学
Degree Name工学博士
Degree Discipline环境工程
Keyword微藻 生物膜 硫酸盐 重金属 Rab反应器
Abstract

       黄金是重要的战略及金融储备资源,由于其存量稀少、性质稳定及被赋予尊
贵象征等特点,已经在一定程度上成为生活必需品。然而,由于社会需求的不断
增加,黄金开采和冶炼的难度也在同步增加,其伴生的环境问题也日益突出,尤
其是废水废渣的排放。胶东地区是全国最大的黄金生产基地,但黄金冶炼过程中
会产生废酸、萃余液、含氰废水等,此类废水大多呈酸性,而且具有硫酸盐和重
金属含量高等特点,该类废水的有效处理一直是环保行业的瓶颈之一。目前针对
黄金冶炼废水的处理技术存在成本高、难达标、中水回用率低等诸多问题。然而,通常情况下,冶炼区域的废水通常为冶炼废水与生活污水的混合废水,混合后的废水中含有大量的碳、氮、磷等污染物,大大提高了该区域废水的可生化性。因此,开发新型技术对该区域内废水进行有效处理,探索实现废水资源化利用尤为重要。
       微藻是一类能够进行光合作用的低等生物,广泛应用于食品保健品、化妆品、动物饵料饲料、生物能源和固碳、废水处理等领域。其中,废水中大量的碳、氮、磷、硫等物质,是微藻生长所必需的元素。同时,微藻具有极强的重金属吸附性能。采用微藻进行废水处理,不仅能够减轻环境污染,还可促进微藻生长。开展利用微藻进行黄金冶炼工业区域废水处理的研究,对于识别微藻在极端环境(高酸、高盐、高重金属等)中的生长状况,以及对硫酸盐、重金属去除效果等问题具有重要意义,也可为利用微藻进行工业废水治理及污染水体修复提供技术依据。
       本研究采用了两种不同类型的微藻培养方式,即分别利用鼓泡床光反应器在
悬浮体系下培养微藻,和利用旋转微藻生物膜反应器(RAB)在挂膜培养体系下
培养微藻。本研究针对烟台地区金矿冶炼区域附近,废水中硫酸盐含量及镍、锌、钴、铬等重金属含量较高的特点,首先评价了悬浮微藻在含硫化物模拟废水和含硫酸盐模拟废水中的生长效果,结果显示,在悬浮培养条件下,高浓度硫化物对微藻的生长具有明显的抑制作用,而悬浮微藻可在含高浓度硫酸盐废水中生长。 当在 pH 为 9、水力停留时间(HRT)为 10 天、进水 SO42-浓度为 1g/L 时,悬浮微藻的生长状况最佳,悬浮微藻培养体系对 TN、COD 的去除效果较好,去除效 率分别能达到 84%和 99%,但对 TP、 SO42- 的去除能力较差,其中 TP 的出水浓度略高于进水浓度(藻类释放) , SO42-的去除效率多在 20%附近,且连续培养模式下易发生细胞流失的问题。
       利用旋转微藻生物膜反应器,重点研究了微藻生物膜对于酸性高硫酸盐
(1g/L 、2g/L 、4g/L)模拟废水的处理效果及在该水体环境下反应器的长期运
行状况。结果显示,旋转微藻生物膜反应器对于硫酸盐的去除效率可达 46%,去
除速率达 0.56g/L-day,且微藻生物膜对模拟废水中氨氮、TP、COD 均具有很好
的处理效果,21 天后,去除率分别达到 82.64%、99.69%、98.90%。采用电感耦合等离子光谱技术对微藻生物量中的硫含量进行了检测,发现微藻生物量中的硫含量随着进水 SO42-浓度的提高而提高,说明微藻生物膜能够有效吸收模拟废水体系中的 SO42-。采用高通量测序技术对微藻生物膜处理酸性高含硫酸盐模拟废水前后的微生物群落变化进行分析,结果显示 RAB 反应器培养的微藻生物膜有
着丰富的微生物群落,包括多种蓝细菌、绿藻、硅藻以及酸性还原细菌等。
       利用微藻能够吸附重金属的优势,采用悬浮微藻和微藻生物膜培养体系,分
别对镍(Ni(II))、锌(Zn(II))、钴(Co(II))、铬(Cr(III)) 四种重金属离子进行吸附性研究。在工业废水常见的浓度范围内,采用 4 个固定镍、锌、钴、铬浓度,分别为 81.75mg/L、0.292mg/L、99mg/L 和 25mg/L。结果显示,微藻对重金属的吸附效果随着微藻负载量的增加而提高,对镍、锌、钴、铬的去除效率均能达到 100%,且微藻生物膜对于镍、锌和铬的吸附效果优于悬浮微藻。通过荧光共聚焦显微镜观察发现,微藻生物膜中的胞外聚合物(Extracellular Polymeric Substances,EPS)含量远远高于悬浮微藻中的 EPS 含量,这是造成微藻生物膜对重金属的吸附效果远远好于悬浮微藻的原因。不同微藻负载量下,微藻对重金属的吸附符合二级动力学方程,且微藻对重金属的吸附符合 Freundlich 等温线吸附模型。在此基础上,本研究以镍为例,着重研究了悬浮微藻和微藻生物膜在不同镍浓度(0、10、100、1000、5000 mg/L)、不同 pH(5、7、9)条件下的生长状况,并对微藻吸附重金属的机理进行了深入研究,结果发现,与悬浮微藻相比,微藻生物膜能够耐受浓度为 5000 mg/L 的镍溶液,且当初始镍浓度为 100-1000mg/L 时,微藻生物膜对镍的去除效率可达 90%,并能够实现生长。利用 SYTOX核酸绿细胞技术对吸附镍后的悬浮微藻和微藻生物膜生物量分析发现,微藻生物膜中活细胞含量高于悬浮微藻,这是由于微藻生物膜中大量的 EPS 对藻细胞起到了一定的保护作用。
       最后,利用旋转微藻生物膜反应器,对微藻生物膜在硫酸盐(1000 mg/L)和镍(80 mg/L)的复合模拟废水中的生长及污染物去除效果进行了研究。结果显
示,微藻生物膜在高硫酸盐重金属复合模拟废水中可以生长且对污染物有着一定
的去除效果,镍的存在会在一定程度上抑制微藻生物膜对水体中硫酸盐的去除效
果。
       以上研究说明,相比于传统的悬浮微藻培养体系而言,以 RAB 反应器为基
础的微藻生物膜体系对高浓度硫酸盐、高浓度重金属环境具有更好的耐受性,且
能够在以高浓度硫酸盐和重金属复合环境为基础的模拟废水中生长,并完成对水
体中污染物的去除,这对后续微藻在处理矿业冶炼区域废水方面的研究具有重要
意义。

Other Abstract

      Gold is an important strategic and financial reserve resource. Due to its scarcity, stable nature and noble features, gold has become necessary in life to some extent. However, the difficulty of gold mining and smelting has increased due to the increasing social demand, which cause the associated environmental problems, especially the discharge of wastewater and waste slag. Jiaodong region in Shandong province is recognized as the main source of gold production in China. The process of gold smelting could generate large amounts of waste acid, raffinate and cyanide containing wastewater, most of which are acidic and contain high concentration of sulfate and heavy metals. However, the current techniques for gold smelting wastewater treatment have many problems, such as high cost, hardly meet the wastewater discharge standards, and low reuse rate of reclaimed water, etc. Nonetheless, generally the wastewater in the smelting area is usually the mixed wastewater of smelting wastewater and domestic wastewater. The mixed wastewater contains large amounts of pollutants including carbon, nitrogen and phosphorus, which greatly improves the biodegradability of the wastewater in such area. Therefore, it is particularly important to develop new treatment techniques for gold smelting wastewater treatment and realize the utilization of wastewater resources.

      Microalgae, a group of primary organisms, which are capable of performing photosynthesis and can be used in many fields including food and health care industries, cosmetics industries, animal feed industries, bioenergy, carbon sequestration, wastewater treatment and so on. Generally, wastewater often contains large amount of carbon, nitrogen, phosphorus, sulfur and other nutrients, which are necessary for the growth of microalgae. Meanwhile, microalgae have strong ability in absorbing heavy metal ions. Therefore, wastewater treatment by microalgae can realize both environmental protection and the cultivation of microalgae biomass. It is significant to investigate treating gold smelting wastewater using microalgae by studying the growth of microalgae in relatively extreme water environment, the performance of wastewater treatment, and the subsequent direct use of microalgae for industrial wastewater and polluted water treatment and the restoration.

       Our study was carried out using two different microalgae cultivation systems, which were the suspended microalgae cultivated by bubble column and the algal biofilm cultivated by the Rotating Algal Biofilm (RAB) reactor created by our lab. The wastewater around the gold smelting area in Yantai region has high concentrations of sulfate and heavy metals such as nickel, zinc, cobalt, chromium. Aiming at the features above, the growth of microalgae in the synthetic wastewater containing high concentration of sulfide and sulfate was evaluated. The results indicated that the growth of suspended algal cells were completely inhibited at high concentration of sulfide, but showed the best growth performance at 1g/L SO42-, pH of 9 and hydraulic retention time (HRT) of 10 days. The suspended microalgae cultivation system showed the best TN and COD removal efficiency, which are 84% and 99% respectively. However, the removal performance of TP and SO42- were poor. The TP concentration of the effluents was even higher than that of the influents, and the SO42- removal efficiency of most conditions were around 20%. What’s more, the cell waste problem happened in the continuous suspended culture mode.

       The treatment performance of the acidic high sulfate (1g/L, 2g/L, 4g/L) synthetic wastewater treated by the algal biofilm was studied particularly using the RAB reactor. The long-term operation status of the RAB reactor in this water environment was also monitored. The results showed that the algal biofilm in RAB reactor had a sulfate removal efficiency of 46% and a removal rate of 0.56g/L-day. The removal performances of the algal biofilm on ammonia, TP and COD in the acidic synthetic wastewater were excellent, with the removal rate up to 82.64%, 99.69% and 98.90%, respectively. The sulfur content in the biomass were detected by inductively coupled plasma spectrometry (ICP-MS). The results showed that the biomass sulfur content increased with the increase of SO42- concentrations, indicating that the algal biofilm could effectively absorb sulfate in the synthetic wastewater system. The variation of the microbial community of the algal biofilms treating the acidic sulfur-containing synthetic wastewater was characterized by high-throughput sequencing technology. The results showed that the algal biofilms in RAB reactor had a high species richness of microbial communities, including various cyanobacteria, green algae, diatoms and acid reducing bacteria, etc. The work further studied the sulfur removal mechanism of microalgae, which laid a foundation for the subsequent research on the treatment of gold smelting wastewater by microalgae.

       The adsorption performance of nickel (Ni (II)), zinc (Zn (II)), cobalt (Co (II)) and chromium (Cr (II)) by suspended microalgae and algal biofilm was studied. Within the typical concentration range of industrial wastewater, the four metal ions (nickel, zinc, cobalt and chromium) were prepared to reach a concentration of 81.75mg/L, 0.292mg/L, 99mg/L and 25mg/L, respectively. The adsorption performance of microalgae on heavy metal ions increased with the increase of the biomass loading, with the removal efficiencies of nickel, zinc, cobalt and chromium of almost 100%. What’s more, the algal biofilm showed better adsorption performance of nickel, zinc and chromium than the suspended microalgae. The fluorescence confocal microscopy results showed that the content of EPS in microalgae biofilms was much higher than that in suspended microalgae, which was the reason for the better adsorption performance of microalgae biofilms on heavy metals than that of suspended microalgae. The kinetic parameters of metal adsorption followed the pseudo-second order kinetics, and the adsorption behavior could be interpreted by the Freundlich isotherm model. Furthermore, take nickel as the model metal ion, the growth performances of the suspended microalgae and algal biofilm cultivated in the water environment with different nickel concentrations (0, 10, 100, 1000, 5000 mg/L) and different pH (5, 7, 9) were studied. The adsorption mechanism of heavy metal ions by microalgae were also studied. The results showed that compared to suspended microalgae, the algal biofilm can tolerate a nickel concentration as high as 5000 mg/L. The nickel removal efficiency could reach to 90% at the initial nickel concentration of 100-1000 mg/L and the algal biofilm could realize the growth in such environment. The SYTOX Green dye analytical method was used to distinguish the membrane-damaged cells from the intact cells in the biomass of suspended microalgae and algal biofilm after adsorption of nickel. The results showed that the amount of intact cells in the algal biofilm was higher than that in suspended microalgae, which was contributed to the protection by large amounts of EPS in algal biofilm.

       The growth of algal biofilm and pollutant removal performances in RAB reactors were studied in synthetic wastewater with sulfate concentration of 1000 mg/L and nickel concentration of 80 mg/L. The results showed that the algal biofilm could grow and removal nutrients in the synthetic high sulfate and heavy meatal containing wastewater. The existence of nickel could affect the sulfate removal performance by the algal biofilm to some extent.

       The research showed that compared with the traditional suspended microalgae cultivation system, the biofilm cultivation system based on RAB reactors had better tolerance of high concentration sulfate environment and high concentration of heavy metals environment, and showed good growth performance in the synthetic wastewater with both the high concentration sulfate and heavy metals, succeding in removing pollutants in water. The results are significant for the further study of utilizing microalgae in the treatment of wastewater in mining smelting area.

Subject Area环境科学技术
MOST Discipline Catalogue工学
Language中文
Document Type学位论文
Identifierhttp://ir.yic.ac.cn/handle/133337/24096
Collection中国科学院烟台海岸带研究所
中科院海岸带环境过程与生态修复重点实验室
Recommended Citation
GB/T 7714
周浩媛. 微藻对高硫酸盐及重金属模拟废水的处理与机理研究[D]. 中国科学院大学. 周浩媛,2019.
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