The comparison of growth and nutrient removal efficiency of Chlorella pyrenoidosa in settled and activated sewage

The microscopic green alga, Chlorella pyrenoidosa was grown in settled and activated sewage under two different culture systems, batch and semi-continuous. Good growth was obtained in both types of wastewater and the algal production was comparable to and even higher than that found in commercial Bristol medium. The semi-continuous culture supported more growth than the batch system. There was a close relationship between algal growth and the amount of nutrient removed from both settled and activated sewage. A more rapid drop in NH(4)(+)-N was found in settle rather than activated sewage. The NH(4)(+)-N of settled sewage dropped from its initial 27 to 5 mg litre(-1) in both culture systems. On the other hand, the NO(3)(-)-N of activated sewage started to decrease from Day 2 onwards and the final NO(3)(-)-N concentration was less than 1 mg litre(-1) (over 90% removal efficiency). The amount of total inorganic nitrogen being reduced due to algal culture was similar in both types of sewage. The changes of phosphate content followed the same trend in both sewage, the P concentration increased slightly in the first two days then decreased, especially in the semi-continuous cultures. The final ortho-P in the sewage treated by Chlorella in semi-continuous culture was less than 5 mg litre(-1) (about 62% reduction). Such removal efficiency was slightly lower than those reported in previous studies. In general, the semi-continuous algal culture appeared to be a more suitable and efficient way for wastewater treatment than the batch system. With respect to the total reduction of wastewater inorganic N and P by means of Chlorella cells, there was no significant difference between settled and activated sewage.     

Dynamics of copper and tetracyclines during composting of water hyacinth biomass amended with peat or pig manure

Composting is one of the post-treatment methods for phytoremediation plants. Due to a high potential of water hyacinth to accumulate pollutants, the physicochemical parameters, microbial activity as well as fates of copper (Cu) and tetracyclines (TCs) were investigated for the different amended water hyacinth biomass harvested from intensive livestock and poultry wastewater, including unamended water hyacinth (W), water hyacinth amended with peat (WP), and water hyacinth amended with pig manure (WPM) during the composting process. Pig manure application accelerated the composting process as evidenced by an increase of temperature, electrical conductivity (EC), NH₄-N, as well as functional diversity of microbial communities compared to W and WP treatments. Composting process was slowed down by high Cu, but not by TCs. The addition of peat significantly increased the residual fraction of Cu, while pig manure addition increased available Cu concentration in the final compost. Cu could be effectively transformed into low available (oxidizable) and residual fractions after fermentation. In contrast, less than 0.5% of initial concentrations of TCs were determined at the end of 60-day composting for all treatments in the final composts. The dissipation of TCs was accelerated by the high Cu concentration during composting. Therefore, composting is an effective method for the post-treatment and resource utilization of phytoremediation plants containing Cu and/or TCs.     

Advanced extraction and lower bounds for removal of pollutants from wastewater by water plants.

The capacity to reach lower bounds for extraction of pollutants from wastewater by four floating aquatic macrophytes--water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), salvinia (Salvinia rotundifolia), and water primroses (Ludvigia palustris)--is investigated. It is shown that the following lower bounds can be established for wastewater purification with water hyacinth: biochemical oxygen demand (BOD), 1.3 mg/L; chemical oxygen demand (COD), 11.3 mg/L; total suspended solids (TSS), 0.5 mg/L; turbidity, 0.7 NTU; ammonia, 0.2 mg/L; and phosphorus, 1.4 mg/L. Also, the following lower bounds can be established for wastewater purification with water lettuce: BOD, 1.8 mg/L; COD, 12.5 mg/L; TSS, 0.5 mg/L; turbidity, 0.9 NTU; ammonia, 0.2 mg/L; and phosphorus, 1.6 mg/L. These lower bounds were reached in 11- to 17-day experiments that were performed on diluted wastewater with reduced initial contents of the tested water quality indicators. As expected, water hyacinth exhibited the highest rates and levels of pollutant removal, thereby producing the best lower bounds of the water quality indicators. Given the initially low levels, BOD was further reduced by 86.3%, COD by 66.6%, ammonia by 97.8%, and phosphorus by 65.0% after 11 days of a batch experiment. The capacity of water plants to purify dilute wastewater streams opens new options for their application in the water treatment industry.     

Eichhornia crassipes capability to remove naphthalene from wastewater in the absence of bacteria

The aim of the current study was to investigate the potential of an aquatic plant, the water hyacinth (Eichhornia crassipes) devoid rhizospheric bacteria, to reduce naphthalene (a polyaromatic hydrocarbon) present in wastewater and wetlands.The capability of sterile water hyacinth plants to remove naphthalene from water and wastewater was studied in batch systems. Water hyacinths enhance the removal of pollutants through their consumption as nutrients and also through microbial activity of their rhizospheric bacteria.Experimental kinetics of naphthalene removal by water hyacinth coupled with natural rhizospheric bacteria was 100% after 9 d. Plants, decoupled of rhizospheric bacteria, reduced naphthalene concentration up to 45% during 7 d. Additionally, naphthalene uptake by water hyacinth revealed a biphasic behavior: a rapid first phase completed after 2.5 h, and a second, considerably slower rate, phase (2.5-225 h). In conclusion, water hyacinth devoid rhizospheric bacteria reduced significantly naphthalene concentration in water, revealing a considerable plant contribution in the biodegradation process of this pollutant.     

Effect of immobilized microalgal bead concentrations on wastewater nutrient removal

A unicellular green microalga, Chlorella vulgaris, entrapped in calcium alginate as algal beads were employed to remove nutrients (N and P) from simulated settled domestic wastewater. A significantly higher nutrient reduction was found in bioreactors containing algal beads (at concentrations ranging from 4 to 20 beads ml(-1) wastewater) than the blank alginate beads (without algae). A complete removal of NH(4)(+)-N and around 95% reduction of PO(4)(3-)-P was achieved within 24 h of treatment in bioreactors having the optimal algal bead concentration (12 beads ml(-1), equivalent to 1:3 algal beads:wastewater, v/v). The NH(4)(+)-N removal was significantly lower at low (around 4 beads ml(-1)) and high (>15 beads ml(-1)) algal bead concentrations. On the other hand, the effect of bead concentration on phosphate removal was less obvious, and bead concentrations ranging from 8 to 20 beads ml(-1) showed comparable percentages of phosphate reduction. Algal uptake and adsorption on alginate gels were found to be the major processes involved in the removal of N and phosphate in the present study. In addition, NH(4)(+)-N could be lost via ammonia volatilization while PO(4)(3-)-P was removed by chemical precipitation, as alkaline pH was recorded in the immobilized microalgal treatment system.     

Municipal landfill leachate treatment for metal removal using water hyacinth in a floating aquatic system.

Experiments were carried out to investigate the ability of water hyacinth (Eichhornia crassipes) to remove five heavy metals (cadmium, chromium, copper, nickel, and lead) commonly found in leachate. All experiments were conducted in batch reactors in a greenhouse. It was found that living biomass of water hyacinth was a good accumulator for copper, chromium, and cadmium. The plants accumulated copper, chromium, and cadmium up to 0.96, 0.83, and 0.50%, respectively, of their dry root mass. However, lead and nickel were poorly accumulated in water hyacinth. Also, nonliving biomass of water hyacinth dry roots showed ability to accumulate all metals, except Cr(VI), which was added in anionic form. The highest total metal sorption by nonliving dry water hyacinth roots was found to take place at pH 6.4. The current research demonstrates the potential of using water hyacinth for the treatment of landfill leachate containing heavy metals.     

凤眼莲在城市重污染河道修复中的应用

外港河是秦淮河重要支流,长期以来遭受严重污染。2006年4月份起对外港河进行了综合生态治理。在前期清淤和截污的基础上,7月份开始引种凤眼莲。在上游排污口附近和外港河河口段分别设置的4个生态区以及河面上布设的水面载体内全面放养以凤眼莲为主的浮水植物。经过5个多月的初步治理,外港河水体透明度从40 cm以下提高到120 cm左右,COD下降了70.4％,TSS、TN和NH₃-N分别下降了39.6％、49.7％和21.8％。结果证明,凤眼莲在净化严重污染的河道方面起到了良好的效果,引种凤眼莲治理城市重污染河道是切实可行的;此外,用PVC管设计制作的水面载体来放养浮水植物可以点缀水面环境,美化城市河道景观。     

Mercury uptake and accumulation by four species of aquatic plants

The effectiveness of four aquatic plants including water hyacinth (Eichornia crassipes), water lettuce (Pistia stratiotes), zebra rush (Scirpus tabernaemontani) and taro (Colocasia esculenta) were evaluated for their capabilities in removing mercury from water. The plants were exposed to concentrations of 0 mg/L, 0.5 mg/L or 2 mg/L of mercury for 30 days. Assays were conducted using both Microtox (water) and cold vapor Atomic Absorption Spectroscopy (AAS) (roots and water). The Microtox results indicated that the mercury induced acute toxicity had been removed from the water. AAS confirmed an increase of mercury within the plant root tissue and a corresponding decrease of mercury in the water. All species of plants appeared to reduce mercury concentrations in the water via root uptake and accumulation. Water lettuce and water hyacinth appeared to be the most effective, followed by taro and zebra rush, respectively.     

The potential use of constructed wetlands in a recirculating aquaculture system for shrimp culture

A pilot-scale constructed wetland unit, consisting of free water surface (FWS) and subsurface flow (SF) constructed wetlands arranged in series, was integrated into an outdoor recirculating aquaculture system (RAS) for culturing Pacific white shrimp (Litopenaeus vannamei). This study evaluated the performance of the wetland unit in treating the recirculating wastewater and examined the effect of improvement in water quality of the culture tank on the growth and survival of shrimp postlarvae. During an 80-day culture period, the wetland unit operated at a mean hydraulic loading rate of 0.3 m/day and effectively reduced the influent concentrations of 5-day biochemical oxygen demand (BOD5, 24%), suspended solids (SS, 71%), chlorophyll a (chl-a, 88%), total ammonium (TAN, 57%), nitrite nitrogen (NO2-N, 90%) and nitrate nitrogen (NO3-N, 68%). Phosphate (PO4-P) reduction was the least efficient (5.4%). The concentrations of SS, Chl-a, turbidity and NO3-N in the culture tank water in RAS were significantly (P相似文献   

有效微生物菌与水生植物联合净化珍珠蚌养殖废水

以无有效微生物(EM)菌与水生植物的珍珠蚌养殖水体(NSE)作为对照组,对EM菌(EM)、苦草+菹草(VP)、水芹菜+水葱(OS)、苦草+菹草+EM菌(VPE)以及水芹菜+水葱+EM菌(OSE)净化珍珠蚌养殖废水的效果进行了对比研究。实验结果表明,EM、VP、OS对珍珠蚌养殖水体N、P均有较好的净化效果,VPE与OSE去N、P效果更佳。净化28 d后5组合中VPE对NH4+-N的去除效果最好,去除率达98.79%;OSE对NO2-N与TN的去除效果最佳,去除率分别达88.09%和91.53%;TP的去除率VPE最高,达91.75%;而COD的去除率以VP最高,达94.97%,效果好于VPE与OSE;EM池水体DO质量浓度第8天达到峰值(9.88±0.61)mg/L,VP、OS、VPE与OSE均在第16天左右达到峰值。实验数据还表明,EM净化水体效果与VP、OS、VPE和OSE均存在显著性差异,对照组NSE对水体的净化效果不明显。     

城市污水厂污泥替代营养盐培养海水小球藻的研究

为了城市污水厂污泥的资源化利用,对污泥替代F/2培养基培养海水小球藻(Chlorella pacifica)进行了研究。首先采用研磨-离心法制备污泥抽提液,将其与F/2培养基按体积比7∶3混合,接种微藻并在优化的条件下培养6 d,逐日测定混合液中无机氮、磷的浓度,培养结束后测定微藻生物量以及干藻中蛋白质、氨基酸和重金属含量。结果表明,将微藻在最佳条件下培养6 d后,混合液中PO34--P、NO2--N、NH4+-N和NO3--N的吸收率分别达到97.32%、96.72%、97.55%和78.13%;与F/2培养基对照组相比,混合液中微藻的生物量增加11.5%;蛋白质、必需氨基酸和非必需氨基酸的含量变化不大。另外,干藻中的重金属含量符合饲料行业标准的要求。     

生物质材料预处理餐饮废水

采用4种廉价的生物质材料（水葫芦、柚子皮、木屑、核桃壳）用于餐饮废水的预处理。通过静态烧杯实验,研究了各生物质材料预处理废水的效果及最佳处理条件。结果表明,生物质材料对废水中COD的去除率均在45％以上,油脂吸附量为4～16mg／g,最优吸附材料为水葫芦,COD去除率达65％,油脂吸附量为16mg／g;水葫芦和柚子皮的最佳处理条件为：粒径〈0．2mm,投加量为20g／L,废水pH为4,处理时间为2h,温度为20℃;木屑和核桃壳的最佳实验条件为：粒径〈0．2mm,投加量为28g／L,pH为2,处理时间为2．5h,温度为20℃。生物质对餐饮废水的预处理,为废水中大量有机物和废弃油脂的去除提供了新思路和途径。     

Treatment of tannery wastewater in a pilot-scale hybrid constructed wetland system in Bangladesh

This paper reports the pollutant removal performances of a hybrid wetland system in Bangladesh for the treatment of a tannery wastewater. The system consisted of three treatment stages: a subsurface vertical flow (VF) wetland, followed by a horizontal flow (HF) and a VF wetland. The wetlands were planted with common reed (Phragmites australis), but employed different media, including organic coco-peat, cupola slag and pea gravel. In the first stage, experimental results demonstrated significant removal of ammonia (52%), nitrate (54%), BOD (78%), and COD (56%) under high organics loading rate (690 g COD m⁻² d⁻¹); simultaneous nitrification, denitrification, and organics degradation were attributed to the unique characteristics of the coco-peat media, which allowed greater atmospheric oxygen transfer for nitrification and organic degradation, and supply of organic carbon for denitrification. The second stage HF wetland produced an average PO₄ removal of 61%, primarily due to adsorption by the iron-rich cupola slag media. In the third treatment stage, which was filled with gravel media, further BOD removal (78%) from the tannery wastewater depleted organic carbon, causing the accumulation of NO₃ in the wastewater. Overall, the average percentage removals of NH₃-N, NO₃-N, BOD, COD, and PO₄ were 86%, 50%, 98%, 98% and 87%, respectively, across the whole hybrid system. The results provided a strong evidence to support widespread research and application of the constructed wetland as a low-cost, energy-efficient, wastewater treatment technology in Bangladesh.     

Performance of mixed algae for treatment of slaughterhouse wastewater and microbial community analysis

This study investigated organic matter (OM) and nutrient removal efficiency of mixed algal species from slaughterhouse wastewater (SWW) by using photo-bioreactor. For this purpose, different dilution multiples of 10, 4, and 2 were applied to the SWW, and pure wastewater was finally used for algal cultivation. OM and nutrient removal performance in an algal photo-bioreactor were severely affected by the dilution ratio. After 7 days of cultivation, the highest removal percentages of total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) were 89.6, 70.2, and 96.2 %, respectively. Furthermore, the changes in eukaryotic algae and cyanobacterial species in the algal photo-bioreactors were investigated using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results indicated that cyanobacterial species were more efficient than eukaryotic species in removing nutrients from the SWW. This study suggests that mixed algal photo-bioreactors could be used efficiently in the treatment of SWW.

     

废水营养比对固定化藻菌去除污染物的影响及动力学研究

海藻酸钙作载体的固定化藻菌小球,经壳聚糖覆膜后,用于模拟废水的处理。通过研究废水初始氨氮浓度及碳氮比对固定化藻菌小球处理效果的影响,发现初始氨氮浓度为50 mg/L时,氨氮的去除率达最高值74.4%;碳氮比为35∶1时,COD去除率达最高值77.7%。系统最佳氮磷比与碳氮比分别为5∶1和35∶1。固定化藻菌降解有机物的动力学过程为一级不可逆生化反应过程,其降解速率常数约为0.099 h-1。     

Application of a constructed wetland for industrial wastewater treatment: a pilot-scale study

The main objective of this study was to examine the efficacy and capacity of using constructed wetlands on industrial pollutant removal. Four parallel pilot-scale modified free water surface (FWS) constructed wetland systems [dimension for each system: 4-m (L)x1-m (W)x1-m (D)] were installed inside an industrial park for conducting the proposed treatability study. The averaged influent contains approximately 170 mg l(-1) chemical oxygen demand (COD), 80 mg l(-1) biochemical oxygen demand (BOD), 90 mg l(-1) suspend solid (SS), and 32 mg l(-1) NH(3)-N. In the plant-selection study, four different wetland plant species including floating plants [Pistia stratiotes L. (P. stratiotes) and Ipomoea aquatica (I. aquatica)] and emergent plants [Phragmites communis L. (P. communis) and Typha orientalis Presl. (T. orientalis)] were evaluated. Results show that only the emergent plant (P. communis) could survive and reproduce with a continuous feed of 0.4m(3)d(-1) of the raw wastewater. Thus, P. communis was used in the subsequent treatment study. Two different control parameters including hydraulic retention time (HRT) (3, 5, and 7d) and media [vesicles ceramic bioballs and small gravels, 1cm in diameter] were examined in the treatment study. Results indicate that the system with a 5-d HRT (feed rate of 0.4m(3)d(-1)) and vesicles ceramic bioballs as the media had the acceptable and optimal pollutant removal efficiency. If operated under conditions of the above parameters, the pilot-plant wetland system can achieve removal of 61% COD, 89% BOD, 81% SS, 35% TP, and 56% NH(3)-N. The treated wastewater meets the current industrial wastewater discharge standards in Taiwan.     

Mycoremediation—a prospective environmental friendly technique of bioseparation and dewatering of domestic wastewater sludge

INTRODUCTION: Environmental safe and friendly management and disposal of wastewater sludge is a problem of every treatment plant throughout the world. Bioseparation and dewaterability of raw domestic wastewater sludge were evaluated for proper management and disposal by mycoremediation, i.e., using prior grown 2% (v/v) spore suspension of filamentous fungal (Mucor hiemalis Wehmer) broth inoculation, which were grown in 2% (w/v) solution of malt extract and wheat flour for 48-60 h in orbital shaker. DISCUSSION: Within 2-3 days of treatment application, encouraging results were achieved in total dry solids (TDS), total suspended solid (TSS), turbidity, chemical oxygen demand (COD), specific resistance to filtration (SRF), and pH due to fungal treatment in recognition of bioseparation and dewaterability of wastewater sludge compared to control. The significant reduction of TDS was remarked at fungal biomass (FB) in wheat flour (WF) treatment. The removal of TSS, turbidity, COD, and SRF were observed 96.0%, 99.4%, 92.6%, and 97.6%, respectively, in supernatant at 5 days by FB in WF. The SRF measuring the dewaterability was decreased with maximum (0.26 × 10(-12) mg/kg) equivalent to 95.5% at 2 days in FB in WF also. FB in WF broth is a potential, environmental friendly, comparatively low-cost biological technique which might play the significant role for bioremediation and bioseparation of domestic wastewater sludge. The present technique may bring a dynamic change in treatment of wastewater in future.     

Constructed treatment wetland: a study of eight plant species under saline conditions

A series of investigations was conducted to evaluate the feasibility of using constructed treatment wetlands to remove pollutants from saline wastewater. Eight emergent plants; cattail, sedge, water grass, Asia crabgrass, salt meadow cordgrass, kallar grass, vetiver grass and Amazon, were planted in experimental plots and fed with municipal wastewater that was spiked with sodium chloride (NaCl) to simulate a saline concentration of approximately 14-16 mScm-1. All macrophytes were found tolerant under the tested conditions except Amazon and vetiver grass. Nutrient assimilation of salt tolerant species was in the range of 0.006-0.061 and 0.0002-0.0024 gm-2d-1 for nitrogen and phosphorus, respectively. Treatment performances of planted units were found to be 72.4-78.9% for BOD5, 43.2-56.0% for SS, 67.4-76.5% for NH3-N and 28.9-44.9% for TP. The most satisfactory plant growth and nitrogen assimilation were found for cattail (Typha angustifolia) though the plant growth was limited, whereas Asia crabgrass (Digitaria bicornis) was superior for BOD5 removal. Both were evaluated again in a continuous flow constructed wetland system receiving saline feed processing wastewater. A high removal rate regularly occurred in long-term operating conditions. The reduction in BOD5, SS, NH3-N and TP was in the range of 44.4-67.9%, 41.4-70.4%, 18.0-65.3% and 12.2-40.5%, respectively. Asia crabgrass often provided higher removal especially for BOD5 and SS removal. Nutrient enriched wastewater promoted flourishing growth of algae and plankton in the surface flow system, which tended to reduce treatment performance.     

凤眼莲-固定化氮循环细菌联合作用对富营养化水体原位修复的研究

应用生态工程技术和原理,在夏季利用凤眼莲（Eichhornia crassipes Mart.）结合固定化氮循环菌对富营养化水体进行原位修复研究。试验结果表明,凤眼莲+固定化氮循环细菌联合作用和单独的凤眼莲处理对富营养化水体总氮和铵态氮去除之间存在显著的差异,凤眼莲+固定化氮循环细菌联合作用对富营养化水体中总氮和铵态氮的去除率分别达77.2%和49.2%;而凤眼莲处理则分别达73.7%和32.3%;但两者对富营养化水体中硝态氮的去除没有显著差异。接种固定化氮循环微生物有利于水体中Chla、COD_Mn的降低和水体透明度的提高,但两者没有明显的差异。当凤眼莲处理系统接种固定化氮循环细菌时,除了氨化细菌变化不明显外,亚硝化菌,硝化菌,反硝化菌群数量比单独凤眼莲处理系统增加1～1.5个数量级,且接种固定化氮循环细菌还有利于凤眼莲生物量及其体内氮积累量的增加。     

模糊综合评价在氧化沟能耗评价中的应用

在对环太湖流域4座采用氧化沟工艺的城市污水处理厂进行能耗调研的基础上,以吨水位能耗(E)、生化段装机容量(η)、有机物去除量(ΔCOD)、氨氮去除量(ΔNH3-N)、总磷去除量(ΔTP)作为评价氧化沟法城市污水厂能耗的指标,结合隶属度函数,应用单因素模糊综合评价法对所调研的污水处理厂进行能耗水平定量评价。得出A污水处理厂的能耗级别为二级,B和C污水处理厂的能耗级别为三级,D污水处理厂能耗级别为五级。级别越高能耗越大。