Kinetic and growth parameters of Arthrospira (Spirulina) platensis cultivated in tubular photobioreactor under different cell circulation systems

Arthrospira platensis was cultivated in tubular photobioreactor in order to evaluate growth and biomass production at variable photosynthetic photon flux density (PPFD = 60, 120, and 240 μmol photons m(-2)s(-1)) and employing three different systems for cell circulation, specifically an airlift, a motor-driven pumping and a pressurized system. The influence of these two independents variables on the maximum cell concentration (X(m)), cell productivity (P(x)), nitrogen-to-cell conversion factor (Y(X/N) ), photosynthetic efficiency (PE), and biomass composition (total lipids and proteins), taken as responses, was evaluated by analysis of variance. The statistical analysis revealed that the best combination of responses' mean values (X(m) = 4,055 mg L(-1), P(x) = 406 mg L(-1)day(-1), Y(X/N) = 5.07 mg mg(-1), total lipids = 8.94%, total proteins = 30.3%, PE = 2.04%) was obtained at PPFD = 120 μmol photons m(-2)s(-1); therefore, this light intensity should be considered as the most well-suited for A. platensis cultivation in this photobioreactor configuration. The airlift system did not exert any significant positive statistical influence on the responses, which suggests that this traditional cell circulation system could successfully be substituted by the others tested in this work.     

毛枝藻对人工污水脱氮除磷能力的研究

文章探究了2株毛枝藻(Stigeoclonium sp.)SHY-370及HB1617在不同初始氨氮浓度以及不同氮磷比条件下的生长情况与氮磷去除能力。结果表明氨氮浓度对2株毛枝藻的生长及TP去除能力均有一定的影响, SHY-370可耐受最大氨氮浓度为10 mg/L, HB1617为5 mg/L;氨氮浓度为1—10 mg/L时SHY-370及HB1617对其去除率均达到97%以上,最大去除速率为3.98 mg/(L·d)。氮磷比对SHY-370的生长影响不大,但在氮磷比大于20时HB1617的生长受到抑制; SHY-370对NO_3~--N去除的最佳氮磷比为10—40, HB1617为2—10;氮磷比为2时水体中TP的含量超过了SHY-370及HB1617所能去除的最大值,去除率较低。实验结果表明SHY-370及HB1617在污水深度脱氮除磷方面具有一定的潜力,可考虑将其应用于城市生活污水二级出水(TN≤15 mg/L、TP≤0.5 mg/L、 NH_4~+-N≤5 mg/L)的深度处理。     

Integration of a Coagulation/Flocculation step in a biological sequencing batch reactor for COD and nitrogen removal of supernatant of anaerobically digested piggery wastewater

The supernatant from mesophilic anaerobic digestion of piggery wastewater is characterised by a high amount of COD (4.1 g COD L(-1)), ammonium (2.3g NH(4)(+)-NL(-1)) and suspended solids (2.5 g SS L(-1)). This effluent can be efficiently treated by means of a Sequencing Batch Reactor (SBR) strategy for biological COD, SS and nitrogen removal including a Coagulation/Flocculation step. Total COD and SS reduction yields higher than 66% and 74%, respectively, and a total nitrogen removal (via nitrite) of more than 98% were reached when working with HRT 2.7 days, SRT 12 days, temperature 32 degrees C, three aerobic/anoxic periods, without external control of pH and under limited aeration flow. The inhibition of nitrite oxidizing biomass was achieved by the working free ammonia concentration and the restricted air supply (dissolved oxygen concentration below 1 mg O(2)L(-1)). Since a part of the total COD was colloidal and/or refractory, a Coagulation/Flocculation step was implemented inside the SBR operating strategy to meet a suitable effluent quality to be discharged. Several Jar-Tests demonstrated that the optimal concentration of FeCl(3) was 800 mg L(-1). A respirometric assay showed that this coagulant dosage did not affect the biological activity of nitrifying/denitrifying biomass.     

Pilot-plant-scale outdoor mixotrophic cultures of Phaeodactylum tricornutum using glycerol in vertical bubble column and airlift photobioreactors: studies in fed-batch mode

Pilot-scale (0.19 m column diameter, 2 m tall, and 60 L working volume) outdoor vertical bubble column (BC) and airlift photobioreactors (a split-cylinder (SC) and a draft-tube airlift device (DT)) were compared for fed-batch mixotrophic culture of the microalga Phaeodactylum tricornutum UTEX 640. The cultures were started photoautotrophically until the onset of a quasi-steady-state biomass concentration of 3.4 g L(-)(1). After this, the cultures were supplemented with organic nutrient (glycerol 0.1 M) and a reduced nitrogen source, resulting in an immediate growth rate boost, which was repeated with successive additions of nutrients in all three photobioreactors. During this period the biomass productivity was enhanced compared to photoautotrophic cultures in the three reactors, although differences were found among them. These could be attributed to the different hydrodynamic behavior influencing the transport phenomena inside the cultures. A 25.4 g L(-)(1) maximum biomass concentration was attained in the SC. Further additions of nutrients did not promote any more growth. The consumption of glycerol was quantitative in the first additions but slowed at high biomass concentration, suggesting that a minimum amount of light is needed to sustain growth. No significant effect of the supplied organic nutrient on carotenoids and chlorophylls content was observed, although it had a profound effect on the fatty acid composition. Eicosapentaenoic acid (EPA) content was increased up to 3% (DW) in mixotrophic growth, giving a productivity of 56 mg L(-)(1) d(-)(1), a significant increase compared to the photoautotrophic control, which yielded a maximum EPA content of 1.9% (DW) and a productivity of 18 mg L(-)(1) d(-)(1). The maximum biomass and EPA volumetric yields obtained in this work are comparable with those reported for commercial photoautotrophic monoculture of large quantities of P. tricornutum in closed continuous-run tubular loop bioreactors with tubes that are typically less than 0.08 m in diameter. When the comparison is established in terms of productivities based on the land area occupied, the vertical airlift and bubble-column bioreactors are extraordinarily more productive.     

Improvement of Panax notoginseng cell culture for production of ginseng saponin and polysaccharide by high density cultivation in pneumatically agitated bioreactors

A Panax notoginseng cell culture was successfully scaled up from shake flask to 1.0-L bubble column reactor and concentric-tube airlift reactor. High-density bioreactor batch cultivation was carried out using a modified MS medium. The maximum cell density in batch cultures reached 20.1, 21.0 and 24.1 g/L in the shake flask, bubble column and airlift reactors, respectively, and their corresponding biomass productivity was 950, 1140 and 1350 mg/(L x d) for each. The productivity of ginseng saponin was 70, 96 and 99 mg/(L x d) in the flask, bubble column and airlift reactors, respectively; and the polysaccharide productivity reached 104, 119 and 151 mg/(L x d) for each. Furthermore, a fed-batch cultivation strategy was developed on the basis of specific oxygen uptake rate (SOUR), i.e., sucrose feeding before a sharp decrease of SOUR, and the highest cell density of 29.7 g/L was successfully achieved in the airlift bioreactor on day 17 with a very high biomass productivity of 1520 mg/(L x d). The concentrations of ginseng saponin and polysaccharide reached about 2.1 and 3.0 g/L, respectively, and their productivity was 106 (saponin) and 158 mg/(L x d) (polysaccharide). This work successfully demonstrated the high-density bioreactor cultivation of P. notoginseng cells in pneumatically agitated bioreactors and the reproduction of the shake flask culture results in bioreactors. The cell density, biomass productivity, production titer and productivity of both ginseng saponin and polysaccharide obtained here were the highest that have been reported on a reactor scale for all the ginseng species.     

An optical-density-based feedback feeding method for ammonium concentration control in Spirulina platensis cultivation

Cultivation of Spirulina platensis using ammonium salts or wastewater containing ammonium as alternative nitrogen sources is considered as a commercial way to reduce the production cost. In this research, by analyzing the relationship between biomass production and ammonium- N consumption in the fed-batch culture of Spirulina platensis using ammonium bicarbonate as a nitrogen nutrient source, an online adaptive control strategy based on optical density (OD) measurements for controlling ammonium feeding was presented. The ammonium concentration was successfully controlled between the cell growth inhibitory and limiting concentrations using this OD-based feedback feeding method. As a result, the maximum biomass concentration (2.98 g/l), productivity (0.237 g/l·d), nitrogen-to-cell conversion factor (7.32 gX/gN), and contents of protein (64.1%) and chlorophyll (13.4 mg/g) obtained by using the OD-based feedback feeding method were higher than those using the constant and variable feeding methods. The OD-based feedback feeding method could be recognized as an applicable way to control ammonium feeding and a benefit for Spirulina platensis cultivations.     

Removal of nitrogen and phosphorus by Eucalyptus and Populus at a tertiary treated municipal wastewater sprayfield

Various progenies of Eucalyptus grandis and E. amplifolia, and clones of Populus deltoides, were evaluated for plant removal of nitrogen (N) and phosphorus (P) for 26 months at a municipal waste spray field in north Florida. Tertiary treated wastewater containing 2.73 mg L(-1) nitrate N and 0.30 mg L(-1) total P was applied using sprinkler irrigation (93.8 m3 ha(-1) d(-1)) to fast growing trees utilized for bioenergy. Eucalyptus amplifolia and E. grandis survived and grew very poorly as the result of severe winter injury in two successive years and were not evaluated for nutrient removal. Survival and growth of P. deltoides demonstrated suitability for phytoremediation, and selected clones were evaluated for biomass and nutrient content. Removals of total N (TN) and total P (TP) were greatest for main stem (36% and 44%, respectively) and foliage (44% and 36%, respectively). Low biomass producing clones generally had higher nutrient concentrations, but high biomass producing clones removed more TN and TP. Approximately 789 kg ha(-1) TN and 103 kg ha(-1) TP were removed by the highest biomass producing P. deltoides clone, representing 215% of N and 615% of P inputs.     

Simultaneous cultivation of Spirulina platensis and the toxigenic cyanobacteria Microcystis aeruginosa

Mangueira Lagoon, located in the extreme south of Brazil, has water with physicochemical characteristics such as alkaline pH and carbonate levels propitious for the growth of the cyanobacterium Spirulina platensis. Previously published studies have shown that Mangueira Lagoon water supplemented with small quantities of carbon and nitrogen is suitable for S. platensis cultivation and can significantly reduce production costs. We studied mixed cultures of Spirulina platensis and the toxic cyanobacterium Microcystis aeruginosa using a 2(3) factorial design in which the three factors were the initial biomass concentration of S. platensis and M. aeruginosa and the type of culture medium (100% Zarrouk's medium or 80% Mangueira Lagoon water plus 20% Zarrouk's medium). The highest S. platensis maximum specific growth rate (mu(max)) occurred in the culture with the highest M. aeruginosa biomass concentration and when undiluted culture medium was used (micro(max) = 0.283 d(-1)). The highest M. aeruginosa specific death rate (k) was obtained in the presence of S. platensis (k = 0.555 d(-1)) and was independent of the initial M. aeruginosa biomass concentration and culture medium, demonstrating that S. platensis cultures are not susceptible to contamination by M. aeruginosa. The culture medium had no significant influence (p > 0.05) on S. platensis micro(max) values, indicating that production costs could be reduced by using a medium consisting of 80% Mangueira Lagoon water plus 20% Zarrouk's medium.     

Effects of phosphorus concentration and light intensity on the biomass composition of Arthrospira (Spirulina) platensis

This paper presents the effects of various phosphorus concentrations (10, 50, 250 and 500 mg l(-1) K(2)HPO(4)) on the biomass production and composition of Arthrospira (Spirulina) platensis in relation to light intensity (24, 42 and 60 μE m(-2) s(-1)). The maximum biomass production was 3,592 ± 392 mg l(-1) and this was observed in 250 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1) light intensity after 32 days of cultivation. A maximum specific growth rate (μ(max)) of 0.55 d(-1) was obtained in 500 mg l(-1) K(2)HPO(4) at 60 μE m(-2) s(-1). The protein, lipid and chlorophyll contents of the biomass varied from 33.59 to 60.57 %, 5.34 to 13.33 % and 0.78 to 2.00 %, respectively. The most significant finding was that phosphorus limitation (10 mg l(-1) K(2)HPO(4)) caused a drastic increase of the carbohydrate content (59.64 %). The effect of phosphorus limitation on the carbohydrate content was independent of the light intensity. The accumulated carbohydrates are proposed to be used as substrate for biofuel generation via one of the appropriate biomass energy conversion technologies. Also, it was observed that phosphorus removal is a function of biomass density, phosphorus concentration and light intensity.     

Influence of ammonium chloride feeding time and light intensity on the cultivation of Spirulina (Arthrospira) platensis

This study dealt with the influence of both the feeding time and light intensity on the fed-batch culture of the cyanobacterium Spirulina (Arthrospira) platensis using ammonium chloride as a nitrogen source. For this purpose, a 2(2) plus star central composite experimental design combined with response surface methodology was employed, and the maximum cell concentration (X(m)), the cell productivity (P(X)), and the yield of biomass on nitrogen (Y(X/N)) were selected as the response variables. The optimum values of X(m) (1,833 mg L(-1)) and Y(X/N) (5.9 g g(-1)) estimated by the model at light intensity of 13 klux and feeding time of 17.2 days were very close to those obtained experimentally under these conditions (X(m) = 1,771 +/- 41 mg L(-1); Y(X/N) = 5.7 +/- 0.17 g g(-1)). The cell productivity was a decreasing function of the ammonium chloride feeding time and a quadratic function of the light intensity. The protein and lipid contents of dry biomass collected at the end of cultivations were shown to decrease with increasing light intensity.     

CO₂ from alcoholic fermentation for continuous cultivation of Arthrospira (Spirulina) platensis in tubular photobioreactor using urea as nitrogen source

Carbon dioxide released from alcoholic fermentation accounts for 33% of the whole CO(2) involved in the use of ethanol as fuel derived from glucose. As Arthrospira platensis can uptake this greenhouse gas, this study evaluates the use of the CO(2) released from alcoholic fermentation for the production of Arthrospira platensis. For this purpose, this cyanobacterium was cultivated in continuous process using urea as nitrogen source, either using CO(2) from alcoholic fermentation, without any treatment, or using pure CO(2) from cylinder. The experiments were carried out at 120 μmol photons m(-2) s(-1) in tubular photobioreactor at different dilution rates (0.2 ≤ D ≤ 0.8 d(-1) ). Using CO(2) from alcoholic fermentation, maximum steady-state cell concentration (2661 ± 71 mg L(-1) ) was achieved at D = 0.2 d(-1) , whereas higher dilution rate (0.6 d(-1) ) was needed to maximize cell productivity (839 mg L(-1) d(-1) ). This value was 10% lower than the one obtained with pure CO(2) , and there was no significant difference in the biomass protein content. With D = 0.8 d(-1) , it was possible to obtain 56% ± 1.5% and 50% ± 1.2% of protein in the dry biomass, using pure CO(2) and CO(2) from alcoholic fermentation, respectively. These results demonstrate that the use of such cost free CO(2) from alcoholic fermentation as carbon source, associated with low cost nitrogen source, may be a promising way to reduce costs of continuous cultivation of photosynthetic microorganisms, contributing at the same time to mitigate the greenhouse effect.     

A Vigorous Specialized Microbial Food Web in the Suboxic Waters of a Shallow Subtropical Coastal Lagoon

To examine the extent of the microbial food web in suboxic waters of a shallow subtropical coastal lagoon, the density and biomass of bacteria and protozooplankton were quantified under different dissolved oxygen (DO) levels. In addition, bottom waters of a stratified site were compared with bottom waters of a homogeneous site under periods of high and low biological oxygen production/consumption in the lagoon. At the stratified site, microbial biomass decreased with oxygen decline, from oxia to suboxia, with a recovery of the initial total biomass after a 20-day period of persistent suboxia. A peak in density and biomass of purple sulfur bacteria (PSB) (90 μg C L(-1)) occurred in the suboxic waters 20 days prior to the peak in biomass of ciliates >50 μm (Loxophyllum sp. of 150 μm) (160 μg C L(-1)), demonstrating a top down biomass control. Ciliates >50 μm were positively correlated with PSB and bacteriochlorophyll a (photosynthetic pigment of PSB). Total protozoan biomass reached 430 μg C L(-1) in the suboxic waters of the stratified site, with ciliates >50 μm accounting for 90% of the total ciliate biomass and of 55 % of biomass of protozoa. At the homogeneous site, total protozoan biomass was only 66 μg C L(-1), where flagellates and ciliates <25 μm were the dominant microorganisms. Therefore, as light is available for primary producers in the bottom waters of shallow stratified coastal lagoons or estuaries, one can expect that high primary production of PSB may favor a specialized microbial food web composed by larger microorganisms, accessible to zooplankton that tolerate low DO levels.     

Outdoor and indoor cultivation of Spirulina platensis in the extreme south of Brazil

Water supplemented with 10% or 20% (v/v) of Zarrouk medium was used to cultivate Spirulina platensis in closed and open bioreactors under controlled conditions (30 degrees C, 32.5 micromol m(-2) s(-1), 12 h light/dark photoperiod) and in a greenhouse (9.4 to 46 degrees C, up to 2800 micromol m(-2) s(-1), variable day length photoperiod) using different initial biomass concentrations (X0) in the extreme south of Brazil (32.05 degrees S, 52.11 degrees W). Under controlled conditions the maximum specific growth rate (micromax) was 0.102 d(-1), the biomass doubling time (t(d)) was 6.8 d, the maximum dry biomass concentration (Xmax) was 1.94 g L(-1) and the maximum productivity (Pmax) was 0.059 g L(-)1 d(-1), while the corresponding values in the greenhouse experiments were micromax = 0.322 d(-1), t(d) = 2.2 d, Xmax = 1.73 g L(-1) and Pmax = 0.112 g L(-1) d(-1). Under controlled conditions the highest values for these parameters occurred when X0 = 0.15 g L(-1), while in the greenhouse X0 = 0.4 g L(-1) produced the highest values. These results show that the cultivation of S. platensis in greenhouses in the extreme south of Brazil is technically viable and that the S. platensis inoculum and the concentration of Zarrouk medium can be combined in such a way as to obtain growth and productivity parameters comparable, or superior, to those occurring in bioreactors under controlled conditions of temperature, illuminance and photoperiod.     

膜-生物硝化反应器处理含氨废水效能的研究

研究了膜 生物硝化反应器对含氨废水的处理效能以及分离膜的截留和渗透效能。膜_生物反应器启动迅速 ,在水力停留时间为 1d的情况下 ,反应器最高进水浓度达 80mmol(NH₄⁺-N)·L^-1 ,最高容积负荷达 1 12kg(NH₄⁺ -N)·m^-3·d^-1 ,氨氮去除率保持在 95%以上。试验证明 ,分离膜对微生物有良好的截留作用 ,50天内反应器的污泥浓度从 5g·L^-1 增长到 10g·L^-1 ,分离膜表面附着的生物层则对废水氨氮和亚硝氮有进一步的转化作用。在液位差低于 80cm时 ,提高液位差可增大膜渗透通量 ;液位差超过 80cm后 ,增大液位差的膜渗透通量效应很小 ;其中 ,当液位差为 2 0cm左右时 ,膜通量达 2 . 5 1L·m^-2 ·h^-1 ,阻力最小 [(2 . 6 3× 10^-5)m^-1]。该膜_生物硝化反应器可依靠液位差压力驱动出水 ,无需外加动力。     

耐高浓度氨氮的异养硝化好氧反硝化菌株U1的鉴定及其脱氮特性

【背景】城市垃圾渗滤液是一种成分复杂的有机废水,含氮量高,如果未经处理直接排放到环境中会造成严重的环境污染。【目的】筛选可以耐受垃圾渗滤液中高浓度氨氮并高效去除污水中氮素的异养硝化好氧反硝化菌株,为解决垃圾渗滤液的氮素污染提供功能菌株。【方法】从垃圾渗滤液中筛选分离能耐受高氨氮浓度的菌株,通过测定各菌株的脱氮能力,筛选到一株脱氮能力最强的菌株,命名为U1,通过测定16S rRNA基因序列和生理生化特性确定该菌株为铜绿假单胞菌。进一步研究了菌株U1在不同初始氨氮浓度、碳源、转速、初始pH、碳氮比等单因素变量下的脱氮能力,并结合L₉（3⁴）正交试验研究了菌株U1的最佳脱氮条件。【结果】分离出一株铜绿假单胞菌并命名为U1。该菌株的最优脱氮条件为:初始氨氮浓度为1 000 mg/L,红糖和柠檬酸三钠的混合碳源,pH 6.0,C/N为10,转速为130 r/min,菌株U1的最大总氮去除率为64.37%,最大氨氮去除率为76.73%。对于总氮和氨氮含量分别是2 345 mg/L和1 473.8 mg/L的垃圾渗滤液,菌株U1最大总氮去除率为27.86%...     

Potential of constructed wetlands in treating the eutrophic water: evidence from Taihu Lake of China

Three parallel units of pilot-scale constructed wetlands (CWs), i.e., vertical subsurface flow (VSF), horizontal subsurface flow (HSF) and free water surface flow (FWS) wetland were experimented to assess their capabilities in purifying eutrophic water of Taihu Lake, China. Lake water was continuously pumped into the CWs at a hydraulic loading rate of 0.64 m d(-1) for each treatment. One year's performance displayed that average removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH(4)(+)-N), nitrate nitrogen (NO(3)(-)-N), total nitrogen (TN) and total phosphorous (TP) were 17-40%, 23-46%, 34-65%, 20-52% and 35-66%, respectively. The VSF and HSF showed statistically similar high potential for nutrients removal except NH(4)(+)-N, with the former being 14% higher than that of the latter. However, the FWS wetland showed the least effect compared to the VSF and HSF at the high hydraulic loading rate. Mean effluent TP concentrations in VSF (0.056 mg L(-1)) and HSF (0.052 mg L(-1)) nearly reached Grade III (0.05 mg L(-1) for lakes and reserviors) water quality standard of China. Wetland plants (Typha angustifolia) grew well in the three CWs. We noted that plant uptake and storage were both important factors responsible for nitrogen and phosphorous removal in the three CWs. However, harvesting of the above ground biomass contributed 20% N and 57% P of the total N and P removed in FWS wetland, whereas it accounted for only 5% and 7% N, and 14% and 17% P of the total N and P removed in VSF and HSF CWs, respectively. Our findings suggest that the constructed wetlands could well treat the eutrophic lake waters in Taihu. If land limiting is considered, VSF and HSF are more appropriate than FWS under higher hydraulic loading rate.     

Comparison of two different pneumatically mixed column photobioreactors for the cultivation of Artrospira platensis (Spirulina platensis)

Internal loop airlift and bubble column photobioreactors (PBR) were compared with respect to their performances during cultivation of Artrospira platensis (Spirulina platensis). Culture conditions were kept the same and different parameters were examined through the experiments. It was observed that a higher dry biomass weight and chlorophyll-a concentration was obtained in the airlift PBR yielding a maximum growth rate of 0.45 day(-1), while 0.33 day(-1) was reached in the bubble column PBR. Subsequently, a 17-day of production was carried out in the selected PBR to fully determine the performance of the PBR. Maximum growth rate of 0.47 day(-1) was reached during long term cultivation.     

三种不同小球藻去除亚硝态氮和氨氮能力的研究

为了研究小球藻在不同质量浓度的氨氮和亚硝态氮环境下的去除能力与生长效果,从实验室挑选3株不同的小球藻CV315-1(Chlorella sp.)、CV315-2(Chlorella sorokiniana)和CV315-3(Chlorella pyrenoidosa)分别置于不同质量浓度的氨氮和亚硝态氮模拟污水中,在温...     

Nutrient removal from slaughterhouse wastewater in an intermittently aerated sequencing batch reactor

The performance of a 10 L sequencing batch reactor (SBR) treating slaughterhouse wastewater was examined at ambient temperature. The influent wastewater comprised 4672+/-952 mg chemical oxygen demand (COD)/L, 356+/-46 mg total nitrogen (TN)/L and 29+/-10 mg total phosphorus (TP)/L. The duration of a complete cycle was 8 h and comprised four phases: fill (7 min), react (393 min), settle (30 min) and draw/idle (50 min). During the react phase, the reactor was intermittently aerated with an air supply of 0.8L/min four times at 50-min intervals, 50 min each time. At an influent organic loading rate of 1.2g COD/(Ld), average effluent concentrations of COD, TN and TP were 150 mg/L, 15 mg/L and 0.8 mg/L, respectively. This represented COD, TN and TP removals of 96%, 96% and 99%, respectively. Phase studies show that biological phosphorus uptake occurred in the first aeration period and nitrogen removal took place in the following reaction time by means of partial nitrification and denitrification. The nitrogen balance analysis indicates that denitrification and biomass synthesis contributed to 66% and 34% of TN removed, respectively.     

Effect of temperature and free ammonia on nitrification and nitrite accumulation in landfill leachate and analysis of its nitrifying bacterial community by FISH

The cause of seasonal failure of a nitrifying municipal landfill leachate treatment plant utilizing a fixed biofilm was investigated by wastewater analyses and batch respirometric tests at every treatment stage. Nitrification of the leachate treatment plant was severely affected by the seasonal temperature variation. High free ammonia (NH3-N) inhibited not only nitrite oxidizing bacteria (NOB) but also ammonia oxidizing bacteria (AOB). In addition, high pH also increased free ammonia concentration to inhibit nitrifying activity especially when the NH4-N level was high. The effects of temperature and free ammonia of landfill leachate on nitrification and nitrite accumulation were investigated with a semi-pilot scale biofilm airlift reactor. Nitrification rate of landfill leachate increased with temperature when free ammonia in the reactor was below the inhibition level for nitrifiers. Leachate was completely nitrified up to a load of 1.5 kg NH4-N m(-3)d(-1) at 28 degrees C. The activity of NOB was inhibited by NH3-N resulting in accumulation of nitrite. NOB activity decreased more than 50% at 0.7 mg NH3-N L(-1). Fluorescence in situ hybridization (FISH) was carried out to analyze the population of AOB and NOB in the nitrite accumulating nitrifying biofilm. NOB were located close to AOB by forming small clusters. A significant fraction of AOB identified by probe Nso1225 specifically also hybridized with the Nitrosomonas specific probe Nsm156. The main NOB were Nitrobacter and Nitrospira which were present in almost equal amounts in the biofilm as identified by simultaneous hybridization with Nitrobacter specific probe Nit3 and Nitrospira specific probe Ntspa662.