Simultaneous removal of nitrate and pesticides from groundwater using a methane-fed membrane biofilm reactor

Nitrate and pesticide contaminated ground- and surface-waters have been found around the world as a result of the use of these compounds in agricultural activities. In this study we investigated a biological treatment method to simultaneously remove nitrate and pesticides from contaminated water. Methane was supplied as the sole source of carbon to the microbial culture. A methane-fed membrane biofilm reactor (M-MBfR) was developed in which the methane was supplied through hollow-fiber membranes to a biofilm growing on the membrane surface. A methane-oxidizing culture enriched from activated sludge was used as inoculum for the experiments. Removal of nitrate and the four pesticides atrazine, aldicarb, alachlor, and malathion was examined both in suspended culture and in the M-MBfR. The maximum denitrification rate with suspended culture was 36.8 mg N gVSS(-1) d(-1). With the M-MBfR setup, a hydraulic retention time of approximately one hour was required to completely remove an incoming nitrate concentration of about 20 mg NO3-N l(-1). The microbial culture could remove three of the pesticides (aldicarb, alachlor, and malathion). However, no atrazine removal was observed. The removal rates of both nitrate and pesticides were similar in suspended culture and in membrane-attached biofilm.     

Nitrogen removal from water containing high nitrate nitrogen in a paddy field (wetland).

Nowadays, it has become very common to find in Japan that nitrate nitrogen concentrations are very high in spring water and in well water where the land use of a watershed is agricultural. We have often observed around 50 mg/L of nitrate nitrogen in the spring water where we live. Crops produced in those fields are mainly vegetables such as celery, cabbage, lettuce, carrots, and so on. Green tea is also popular in Japan. In order to produce good quality green tea, farmers apply a great amount of nitrogen fertilizer. This amount can reach up to 1,000 kg/ha in some areas, although the average application amounts to 628 kg/ha in Japan. As a result, ground water that is rich in nitrate flows into the river, which results in a high nitrogen concentration in river water and ground water. Further, this causes a low pH in river water in some tributary rivers in Japan, though this kind of case is very rare. We knew from field tests that if water contained a high nitrogen concentration and was introduced into paddy fields, high nitrogen removal would be performed. This paper presents the outline and results of a system on how to remove nitrogen using paddy fields (wetlands). Further, this paper presents the evaluated results of the removal quantity at the watershed level.     

Simultaneous biological removal of sulphide and nitrate by autotrophic denitrification in an activated sludge system.

The feasibility of an autotrophic denitrification process in an activated sludge reactor, using sulphide as the electron donor, was tested for simultaneous denitrification and sulphide removal. The reactor was operated at nitrate (N) to sulphide (S) ratios between 0.5 and 0.9 to evaluate their effect on the N-removal efficiency, the S-removal efficiency and the product formation during anoxic oxidation of sulphide. One hundred per cent removal of both nitrate and sulphide was achieved at a NLR of 7.96 mmol N-L(-1) x d(-1) (111.44 mg NO3- -N x L(-1) x d(-1)) and at a N/S ratio of 0.89 with complete oxidation of sulphide to sulphate. The oxygen level in the reactor (10%) was found to influence the N-removal efficiency by inhibiting the denitrification process. Moreover, chemical (or biological) oxidation of sulphide with oxygen occurred, resulting in a loss of the electron donor. FISH analysis was carried out to study the microbial population in the system.     

Enhancement of nitrate removal in synthetic groundwater using wheat rice stone

To enhance the efficiency of nitrate removal from synthetic groundwater, wheat rice stone (WRS) and granular activated carbon (GAC) were employed as biofilm carriers for denitrification under different HRT (hydraulic retention time) and C/N ratios. Four different ratios of GAC to WRS (0, 0.5, 1.0, and 2.0) were investigated to determine the most appropriate ratio of GAC and WRS. The NO(3)(-)-N, NO(2)(-)-N, COD levels and pH of the effluent were also investigated under various HRT and C/N ratios. The results showed that the column at a GAC/WRS ratio of 1.0 performed best under a C/N ratio of 0.9 and an HRT of 8 h, with 99% nitrate being removed. In addition, little nitrite accumulation and chemical oxygen demand (COD) were observed in effluent under these conditions. These results demonstrated that, with no addition of phosphor in the influent, the nitrate removal efficiency can be enhanced by WRS because WRS can leach trace elements and phosphor to promote the growth of bacteria.     

浅析环境科学中胶体分离的切向超滤技术

结合研究应用实例,简单介绍了近年来切向超滤技术的机理、滤膜的截流和吸附特性、超滤过程中胶体有机碳的回收率以及渗透行为、该技术在环境科学的胶体有机碳分离方面的应用和存在的问题。利用珠江水系水体的胶体分离试验,验证了切向超滤技术的渗透模型。     

旋转错流式超滤净水工艺在农村饮水中的应用

近年,广西探索了旋转错流式超滤净水工艺在农村饮水工程中的应用,3年多试点运行与观测成果表明,利用该净水工艺开发的成套设备能适应天然地表水源可能出现的较大浊度变化,在没有采取滤清等预处理措施和更换滤膜等情况下,该净水工艺出水流量没有减少,出水水质符合饮用水卫生标准;该工艺设备无需滤清处理即可直接对各类水源的饮水进行净化,可广泛在农村中小型饮水工程中推广应用,能更有效地保障农村饮水安全。     

改性凹凸棒土/纳米铁复合材料去除地下水NO_3~--N的研究

采用液相还原法制备改性凹凸棒土/纳米铁复合材料(简称复合材料),考察了该复合材料的稳定性及其作用下"三氮"(NO_3~--N、NH_4~+-N、NO_2~--N)的变化情况,阐明了地下水环境因素(DO、温度、光照)对复合材料去除NO_3~--N的影响。模拟地下水环境时,3种材料去除NO_3~--N的反应活性顺序为:复合材料纳米铁改性凹凸棒土,且复合材料作用下NH_4~+-N的转化率低,几乎无NO_2~--N生成。DO、温度对复合材料去除地下水NO_3~--N的影响较大;而光照和黑暗环境下,地下水中NO_3~--N的去除率及NH_4~+-N、NO_2~--N的生成量均无明显差异。研究成果旨在为NO_3~--N污染地下水工程修复提供理论依据和技术支撑。     

Preliminary studies using hybrid mediated electrochemical oxidation (HMEO) for the removal of persistent organic pollutants (POPs).

This study investigates the hybrid mediated electrochemical oxidation (HMEO) technology, which is a newly developed non thermal electrochemical oxidation process for organic destruction. A combination of ozone and ultrasonication processes to the mediated electrochemical oxidation (MEO) process is termed as hybrid mediated electrochemical oxidation. The electrochemical cell was developed in this laboratory. In the present study, several organic compounds, such as phenol, benzoquinone and ethylenediaminetetraacetic acid (EDTA), were chosen as the model organic pollutants to be destructed by the hybrid process. The organic destruction was monitored based on the CO2 generation and total organic carbon (TOC) reduction. The HMEO process was found to be extremely effective in the destruction of all the target organics chosen in this study. The information obtained from this study will provide an insight in adopting this technique for dealing with more recalcitrant organics (POPs).     

强化混凝超滤组合工艺对有机污染物去除效能的研究

为了进一步提高水质处理效果,采用强化混凝超滤的组合工艺对湖水进行处理,考察该组合工艺对有机物的去除效能,及影响有机物去除效能的因素。试验结果表明:①强化混凝超滤组合工艺对原水浊度的去除效果较好,对TOC和UV254的去除效果也明显优于传统水处理工艺;②原水中UV254含量的波动,对UV254的去除率和滤后水UV254含量影响并不大。原水中TOC含量的波动,对TOC的去除率有很大的影响,对滤后水TOC含量的影响并不大。TOC的去除率普遍高于UV254的去除率;③根据原水和滤后水SUVA值的变化发现,强化混凝超滤组合工艺对亲水性有机物的去除率大于该工艺对疏水性有机物的去除率。在一定范围内,pH的变化对TOC和UV254去除率变化趋势相反。     

Biological nutrient removal model No.1 (BNRM1).

This paper presents the results of the work carried out by the CALAGUA Group on Mathematical Modelling of Biological Treatment Processes: the Biological Nutrient Removal Model No.1. This model is based on a new concept for dynamic simulation of wastewater treatment plants: a unique model can be used to design, simulate and optimize the whole plant, as it includes most of the biological and physico-chemical processes taking place in all treatment operations. The physical processes included are: settling and clarification processes (flocculated settling, hindered settling and thickening), volatile fatty acids elutriation and gas-liquid transfer. The chemical interactions included comprise acid-base processes, where equilibrium conditions are assumed. The biological processes included are: organic matter, nitrogen and phosphorus removal; acidogenesis, acetogenesis and methanogenesis. Environmental conditions in each operation unit (aerobic, anoxic or anaerobic) will determine which bacterial groups can grow. Thus, only the model parameters related to bacterial groups able to grow in any of the operation units of a specific WWTP will require calibration. One of the most important advantages of this model is that no additional analysis with respect to ASM2d is required for wastewater characterization. Some applications of this model have also been briefly explained in this paper.     

含铁矿物吸附剂除磷机理研究及中试应用

研究了含铁矿物吸附剂吸附含磷废水的各项性能,通过静态试验得出此吸附剂的最佳吸附条件,并以此为依据进行了动态小试试验和中试试验。结果表明,含铁矿物吸附剂的吸附平衡时间为45h,吸附等温线较符合Freundlich方程,pH约为5时吸附量达到最大,除铁离子和铝离子外,水体中无机阴离子和阳离子对磷酸盐的吸附影响不大。用1mol/L的NaOH溶液对饱和吸附剂解吸再生,解吸率达到90%以上。在合适的填充体积和进水流速下,含铁矿物吸附剂连续吸附除磷可以达到良好的效果,中试试验装置连续运行了约105d,出水TP达到了《地表水环境质量标准》(GB3838—2002)(Ⅲ类湖、库)要求。     

纳米铁除磷的影响因素及吸附模式研究

研究了纳米铁投加量、PO3-4浓度、温度、pH对纳米铁去除人工配制磷酸盐废水中PO3-4的影响,并验证了纳米铁对PO3-4的吸附模式.试验表明:磷酸盐初始浓度一定时,增加纳米铁的投加量能增大对PO3-4的吸附;纳米铁投加量一定时,纳米铁的平衡吸附量则随PO3-4初始浓度的增加而增大;25℃时纳米铁对PO3-4的吸附能力最强,升高或降低温度,吸附能力均下降;pH对纳米铁去除PO3-4的影响较大,pH=4时的吸附能力最强,增大或降低pH,吸附能力均下降;纳米铁对PO3-4的吸附符合Freundlich方程而不符合Langmuir方程.     

Arsenic removal by ferric-chloride coagulation--effect of phosphate, bicarbonate and silicate

Jar tests with synthetic water were carried out in order to investigate the effect of phosphate, bicarbonate and silicate on arsenic removal efficiency by in-situ formed ferric hydroxide. Above 12 mg C/L inorganic carbon concentration, the adverse effect of bicarbonate was definite, and resulted in higher remaining arsenic concentration. At all pH values (7.5-7.8) and coagulant dosages (0.84-3.00 mg/L Fe) tested, the negative effect of phosphate on arsenic removal was also evident. In the presence of silicate small ferric-hydroxide colloids were formed, which were able to go through the 0.45 microm pore-size membrane. Compared to silicate-free systems, 2.5-3.5 times higher coagulant dose was needed to achieve the target arsenic concentration in the presence of 14-23 mg/L Si. At higher pH values the adverse effect of silicate was even more significant. All data were merged and multiple linear regression analysis was carried out in order to build up a robust model to predict the residual arsenic concentration if the raw water contains 50-60 microg/L initial arsenic concentration. The estimation was based on the following variables: PO4-P concentration, final pH, Si concentration, Fe(III) dose. The most important influencing factors proved to be the silicate concentration and applied coagulant dosage.     

Application of ultrafiltration in the pulp and paper industry: metals removal and whitewater reuse.

In the pulp and paper industry, the water use minimization is a constant target. One way to reduce water use is to recycle the effluent in a closed-cycle concept. In paper mills, the main source of liquid effluent is the so-called whitewater, which is the excess water, originated from pulp stock dewatering and other fibre contaminated water. This research studied the reuse of paper mill whitewater after membrane ultrafiltration (UF) in the paper machine and in the pulp bleach plant of an integrated mill. Contaminant removal and flux behaviour of the UF system were evaluated. The treatment by ultrafiltration was technically feasible and the treated whitewater had good potential to be reused in some processes in the paper machine. The reuse of ultrafiltered whitewater in the bleaching plant was not recommended because of the high level of soluble calcium present in this stream. Therefore, a combined treatment of the whitewater using the principle of precipitation and ultrafiltration was proposed showing good results and enabling the use of the treated whitewater in the bleach plant.     

Layered double hydroxide (LDH)-coated attapulgite for phosphate removal from aqueous solution

In this study, a composite adsorbent, layered double hydroxide (LDH)-coated attapulgite (LDH-AP), was synthesized and characterized. Its potential application for LDH stabilizer and phosphate (P) removal from aqueous solution was evaluated using the batch mode and continuous mode in a packed bed column. The batch experiments revealed that the data of P adsorption onto LDH-AP could be well described by the Freundlich equation, and the maximum adsorption capacity was estimated to be 6.9 mg/g. The column experiments were conducted in the tap water and the results indicated that the competing anions could slightly decrease phosphate removal. The saturated column was regenerated by 0.2 mol/L of NaOH and the regenerated column was examined for its reuse in phosphate removal. The results of this study suggested that attapulgite could be used as an applicable stabilizer of LDH and LDH-AP could be potentially used as a promising filtration medium for phosphate removal.     

地下水硝酸盐污染原位微生物修复技术研究进展

对于地下水中硝酸盐污染,原位微生物修复技术是一种有发展潜力、效率高且投资少的环境修复技术。但是这种技术也受一些因素的限制。对渗透反应墙技术进行了回顾,讨论了该技术中的有机碳源、电子供体和反硝化细菌的固定等问题,用实例说明应用该技术时需要注意的问题和监测参数,对注射井技术修复地下水硝酸盐污染进行了简单讨论。最后指出,应用微生物法修复地下水硝酸盐污染时要注意细菌污染和修复过程中含水层的渗透性降低或堵塞问题,应加强对治理大面积地下水硝酸盐污染在经济和技术上的可行性论证和研究。     

微絮凝超滤对微污染源水中氨氮去除的试验研究

采用微絮凝超滤工艺对微污染水中氨氮的去除进行了试验研究。结果表明,该工艺能有效地去除水中的氨氮,验证了有机物含量对氨氮去除的影响,同时得出了采用铝盐和铁盐混凝剂的最佳投加量为2.5 mg/L,最佳pH值为5.5~6.0。     

Simultaneous organic stabilization and nitrogen removal in multi-stage biodrum system.

This paper presents the performance of a multi-stage biodrum system applied to domestic wastewater treatment. The organic stabilization and nitrogen removal efficiency in the system was investigated at different hydraulic retention times (HRT) of 12, 6 and 3 hours. The rotational speed of the biodrum was examined at 2,4 and 8 rpm. Average organic removal efficiencies in the system at different HRTs of 12, 6 and 3 hours were 96.3, 94.4 and 90.9%. Simultaneously, average nitrogen removal efficiencies were 91.5, 90.6 and 81.0%. The effect of rotational speed on nitrogen removal efficiencies in the system was clearly observed at a low HRT of 3 hours. The experimental results suggested that optimum HRT in the system was 6 hours. Moreover, they revealed that nitrogen removal efficiencies in the reactors operated at different rotational speed were in the same degree when considering the effluent nitrogen concentration. However, the reactors operated at lower rotational speed needed to employ higher numbers of biodrums (4 stages) than the others with higher rotational speed (3 and 2 stages at 4 and 8 rpm.) in order to achieve similar effluent qualities. At a rotational speed of 2 rpm, maximum nitrogen removal rate was found to be 0.2 kg/m3/d.     

二维电极电解法去除水中硝酸盐试验研究

目前硝酸盐污染已经严重影响了地下水水质,对饮用水安全构成了一定威胁。本研究拟采用电化学方法去除水体中硝酸盐,探究其机理、动力学、影响因素及实际地下水处理方法,为地下水脱氮提供参考。研究结果表明:在无氯离子体系下,30.0 mg/L的硝酸盐在2.0 A电流下电解,其一级反应动力学常数为0.040 h-1,产物中54%为氨氮,46%为氮气。在添加300.0 mg/L氯离子条件下电解,一级反应动力学常数为0.029 h-1,其产物主要为氮气。硝酸盐去除速率随着硝酸盐初始浓度和电流增加而增加,随着氯离子浓度增加而略微减少。对实际地下水水样的电解结果表明,20.0 mg/L的硝酸盐在2.0 A、100.0 mg/L氯离子条件下电解,其一级反应动力学常数为0.031 h-1,产物主要为氮气。二维电极电解过程中,硝酸盐扩散至阴极表面速率较慢,电解效率较低。     

金属基吸附剂去除水体中磷酸盐的研究进展

磷是生命组成必不可少的元素,同时也是导致水体富营养化的主要限制因子之一.目前,磷在地球上的流失率极高,过量的磷进入水体导致水体富营养化的形势日益加剧,迫切需要一种技术高效去除水体中的磷.吸附法由于操作简单、价格低廉,在过去20年里展现出优异的除磷性能,且其中金属基吸附剂尤其是基于锆(Zr)、镧(La)的金属的吸附剂已成...