影响反硝化除磷与厌氧氨氧化耦合的因素

氧对厌氧氨氧化菌有毒,但在颗粒污泥和生物膜中的厌氧氨氧化菌对氧有较高的耐受能力,并且聚磷菌能消耗影响氧氨氧化菌生长的氧。厌氧氨氧化菌的生长无需有机物的参与,聚磷菌释磷需要吸收有机物,少量有机物的加入对厌氧氨氧化菌的活性影响不大。亚硝酸盐是厌氧氨氧化菌氧化氨的电子受体,较高浓度的亚硝酸盐对反硝化聚磷有抑制作用,但合适浓度的亚硝酸盐(该浓度可以通过驯化来提高)可以作为反硝化聚磷菌吸磷的电子受体。厌氧氨氧化过程中有硝酸盐生成,反硝化聚磷菌能利用这部分硝酸盐。另外,两类菌都适宜于中温略偏碱性的环境。因此,通过创造同时对厌氧氨氧化菌和反硝化聚磷菌有利的微生态环境,发挥两者在脱氮除磷方面的协同耦合作用,达到高度脱氮除磷,是极有前景的废水厌氧(缺氧)处理研究方向。     

Spatial heterogeneity of physical and chemical conditions in a tropical reservoir wetland

Abiotic data, such as physical and chemical variables and inorganic nitrogen status were obtained from substrate compartments in four environments in the Lobo reservoir wetlands. The sampling sites were selected by‘in-situ’observation of the hydrological features, the degree of‘openness’to the flow-through of water and macrophyte communities. For each site, three compartments were considered: the sediment, the interstitial water and the overlaying water at the sediment water interface. The pH, electrical conductivity, dissolved oxygen, nitrate, nitrite and ammonium nitrogen, organic matter and moisture content were analyzed in the substrate. The spatial distribution of these properties was associated with the hydrological and nutritional flooding conditions. Lobo wetland sediment may be an efficient buffer system due to its high interstitial and exchangeable ammonium concentrations.     

Effect of inorganic carbon on nitrite accumulation in an aerobic granule reactor.

Pilot scale experiments were performed to evaluate the potential of nitrite type nitrification process with an airlift reactor and granular biomass. Initially, oxygen limitation was used as the main control parameter for accumulating nitrite in the effluent. After 30 d operation, the maximum nitrite conversion rate reached 2.5 kgNO2-N m(-3) d(-1), average diameter of the granule was 0.7 mm. Nitrite type reaction continued over 100 d, but nitrate formation increased after 150 d of operation. Once nitrate formation increased, oxygen limitation could not eliminate nitrite oxidising bacteria from granule. To overcome nitrate formation, laboratory scale batch experiments were conducted and it revealed a high concentration of inorganic carbon which had a significant effect on nitrite accumulation. Following this new concept, inorganic carbon was fed to the pilot scale reactor by changing pH adjustment reagent from NaOH to Na2CO3 and nitrite accumulation was recovered successfully without changing DO concentration. These results show that a high concentration of inorganic carbon is one of the control parameters for accumulating nitrite in biofilm nitrification system.     

Treatment of nitrogen and phosphorus in highly concentrated effluent in SBR and SBBR processes.

Various sludge treatment processes produced supernatant with high ammonia concentration from 500 to 2,000 mgN/L and generally high phosphate concentration. Conversion of ammonia into nitrite via partial nitrification has proven to be an economic way, reducing oxygen and external COD requirements during the nitrification/denitrification process. Two processes with biomass retention are studied simultaneously: the sequencing batch reactor (SBR) and the sequencing batch biofilm reactor (SBBR). At a temperature of 30 degrees C, the inhibition of nitrite-oxidizing bacteria due to high ammonia concentration has been studied in order to obtain a stable nitrite accumulation. This work has confirmed the effect of pH and dissolved oxygen on nitrite accumulation performance. During a two month starting period, both processes led to nitrite accumulation without nitrate production when pH was maintained above 7.5. From a 500 mgN/L effluent, the performance of the SBR, and the SBBR, reached respectively about 0.95gN-NO2-/gN-NH4+, and 0.4gN-NO2-/gN-NH4+. The SBBR appears to be more stable facing disturbances in dissolved oxygen conditions. Finally, the maximal phosphate removal rates obtained in the SBR reached 90%, and 70% in the SBBR, depending on ammonium accumulation in the reactor. Ammonium phosphate precipitation is likely to occur, as was suggested by crystals observation in the reactor.     

Limnological characterization of interdune ponds of Curupu Island,Raposa – MA,Brazil

This study was conducted on four freshwater interdune ponds (Jacaré; Grande; Duna; Banho) located on Curupu Island within the municipality of Raposa (Maranhão State, Brazil). It focused on a diagnosis of the physical and chemical characteristics of the water and sediment in these water bodies, while at the same time obtaining basic data and information that could support the adoption of conservation strategies for the rational use of these ecosystems. Seasonal sampling of water from these ponds was conducted during the months of August, September and November 2008 and 2009 (dry period) and February, May, July 2009 and 2010 (rainy period), for the purpose of obtaining data on temperature, pH, electrical conductivity and dissolved oxygen, ammonium (NH₄), nitrite (NO₂), nitrate (NO₃) and phosphate ion (PO₄) concentrations in the pond water. Sediment sampling also was carried out to determine particle size, carbon, organic matter and phosphorus content. A large variation in most variables, especially the ammonia (NH₄), nitrate (NO₃) and phosphate (PO₄) concentrations, was observed during the study period. The pH values indicated the water in the ponds was mostly alkaline. Based on the average nitrate concentrations (137 μg L^?1 during the dry period; 123 μg L^?1 during the rainy period), the ponds exhibited primarily eutrophic conditions. The sediment samples exhibited a predominance of fine sand with low carbon and organic matter content, able to be classified by their mineral nature. Due to the fragile nature of the studied ecosystems, disciplinary control of grazing activities and tourism in the area is highly recommended, along with adoption of a basic sanitation infrastructure in the community for the purpose of rational and sustainable use of this ecosystem.     

The Mineralisation of Organic Nitrogen: Relationship with Variations in the Water-Table Within a Floodplain of the River Adour in Southwest France

The phenomenon of mineralisation of organic nitrogen has been investigated in a section of the floodplain of the River Adour, between Saubusse and Le Vimport, in southwest France. Water quality parameters have been measured at a number of piezometers within the floodplain: nitrate concentrations measured at the sites were generally negligible during the 15-month period studied, significant levels of dissolved ammonium ion were, however, observed during this period. A mechanism of partial mineralisation has been invoked that considers the breakdown of organic nitrogen within the sediments of the floodplain. The level of the water-table is observed to modulate further oxidation of ammonium ion to nitrite and nitrate ion: low groundwater levels allow aerobic oxidation but increased water levels reduce the production of nitrate. Denitrification and uptake by riparian vegetation appear to be combining rapidly to reduce the nitrate as it is produced. The fine particle size of the floodplain sediments permits the storage of considerable quantities of organic nitrogen and the high level of mineralisation of this stock, responding to variations in the water table, provides an explanation for the increasing nitrate concentrations observed in the river channel in recent years. It is estimated that ca. 24% of the sub-surface organic nitrogen is removed each year.     

Performance of constructed wetland treating wastewater from seafood industry.

Wastewater from seafood industry contains high concentrations of organic matter, nitrogen compounds, and solid matter. Constructed wetland can be used as tertiary treatment and for nutrient recycling. This research studied the performance of nitrogen and suspended solids removal efficiency of a constructed wetland treating wastewater from a seafood-processing factory located at Songkhla, southern Thailand. The existing constructed wetland has dimensions of 85 m, 352 m and 1.5 m in width, length and depth respectively, with an area of about 29,920 m2. The water depth of 0.30 m is maintained in operation with plantation of cattails (Typha augustifolia). Flow rate of influent ranged between 500-4,660 m3/d. Average hydraulic retention time in the constructed wetland was about 4.8 days. Influent and effluent from the constructed wetland were collected once a week and analyzed for pH, temperature, dissolved oxygen (DO), biochemical oxygen demand (BOD5), Suspended solid (SS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), organic nitrogen (Org-N), nitrate (NO3-N), and nitrite (NO2-N). The average removal efficiencies of BOD5, SS, TKN, NH3-N, and Org-N were 84%, 94%, 49%, 52% and 82%, respectively. It was found that the constructed wetland acting as a tertiary treatment process provided additional removal of BOD5, SS and TKN from wastewater from the seafood industry.     

A mass balance study on nitrification and deammonification in vertical flow constructed wetlands treating landfill leachate.

A laboratory-scale, mass-balance study was carried out on the transformation of nitrogenous pollutants in four vertical flow wetland columns. Landfill leachate containing low organic matter, but a high concentration of ammoniacal-nitrogen, was treated under dissolved oxygen concentrations close to saturation. Influent total nitrogen (TN) comprised ammoniacal-nitrogen with less than 1% nitrate and nitrite, negligible organic nitrogen, and very low BOD. Nitrification occurred in three of the four columns. There was a substantial loss of total nitrogen (52%) in one column, whereas other columns exhibited zero to minor losses (< 12%). Nitrogen loss under study conditions was unexpected. Two hypotheses are proposed to account for it: (1) either the loss of TN is attributed to nitrogen transformation into a form (provisionally termed alpha-nitrogen) that is undetectable by the analytical methods used; or (2) the loss is caused by microbial denitrification or deammonification. By elimination and stoichiometric mass balance calculations, completely autotrophic nitrogen-removal over nitrite (CANON) deammonification is confirmed as responsible for nitrogen loss in one column. This result reveals that CANON can be native to aerobic engineered wetland systems treating high ammonia, low organic content wastewater.     

The effect of sulphide and organic matter on the nitrification activity in a biofilm process

Septic wastewater, characterised by the appearance of sulphide, is known to cause problems in sewage systems (corrosion and odour), at treatment plants (e.g. inhibition, sludge bulking) and for human beings (toxicity). Sulphide formation in sewers may be prevented by increasing the redox potential, either by oxygen/air injection (aerobic conditions) or dosage of nitrate (anoxic conditions). The effect on the nitrification capacity in a biofilm process of an anoxic wastewater as compared to a septic wastewater has been studied. The main change in wastewater quality as a result of nitrate dosage is reduced concentrations of organic matter and insignificant sulphide concentrations. The results show that a sulphide concentration of 0.5 mg/1 had a considerable negative effect on the nitrification activity. The sulphide and the higher concentrations of organic matter in the septic wastewater caused together a 30–40% reduction of the nitrification capacity as compared to the anoxic wastewater, even with pre-aeration and pre-precipitation with Fe³⁺. The removal of organic matter in the sewer as a result of the anoxic conditions created by the addition of nitrate, resulted in a maximum nitrification capacity when particulate organic matter was removed by pre-precipitation.     

Rate of nitrate production during a two-stage nitrification batch reaction.

The two steps of nitrification, namely the oxidation of ammonia to nitrite and nitrite to nitrate, often need to be considered separately in process studies. It has been assumed that these two reactions can be described by single Monod models. In this paper, the suitability of the single Monod model for describing nitrite oxidation to nitrate is discussed. The measured rate of nitrate production during a batch reaction is presented. For the system studied it was found that nitrate production actually increased after the completion of ammonia oxidation. It is suggested that the reason for the increase was a combination of: (i) likely competition for oxygen when both substrates were present, and (ii) a decrease in ammonia inhibition of nitrite oxidisers with the removal of ammonia. The result is that a single Monod expression (based on nitrite as the substrate) could not be used to describe nitrate production. In these types of systems the consequence of oxygen limitation and substrate inhibition should also be considered.     

The importance of pre-reservoirs for the control of eutrophication of reservoirs

Pre-reservoirs are small reservoirs, with a water-retention time of a few days, that reduce the phosphorus input in main reservoirs. The process of phosphorus removal involves the biochemical conversion from the dissolved to the particulate forth (mainly phytoplankton) and the sedimentation of this particulate matter. The input variables are light, orthophosphate concentration, temperature of the innowing water and discharge. The phytoplankton activity plays the most important role among the various processes. The maximization of orthophosphate elimination depends on adequate design, construction and operation of pre-reservoirs. A simple calculation procedure for the removal rates of orthophosphate-P has been developed. The efficiency of pre-reservoirs is limited, because the light intensity and the temperature during the winter period are low; on the other hand, discharge is often high to March and April (snowmelt). Although pre-reservoirs are an important tool for reservoir water-quality management, but they cannot substitute remedial action in the catchment area.     

The presence of ammonium facilitates nitrite reduction under PHB driven simultaneous nitrification and denitrification.

For economic and efficient nitrogen removal from wastewater treatment plants via simultaneous nitrification and denitrification the nitrification process should stop at the level of nitrite such that nitrite rather than nitrate becomes the substrate for denitrification. This study aims to contribute to the understanding of the conditions that are necessary to improve nitrite reduction over nitrite oxidation. Laboratory sequencing batch reactors (SBRs) were operated with synthetic wastewater containing acetate as COD and ammonium as the nitrogen source. Computer controlled operation of the reactors allowed reproducible simultaneous nitrification and denitrification (SND). The oxygen supply was kept precisely at a low level of 0.5 mgL(-1) and bacterial PHB was the only electron donor available for denitrification. During SND little nitrite or nitrate accumulated (< 20% total N), indicating that the reducing processes were almost as fast as the production of nitrite and nitrate from nitrification. Nitrite spiking tests were performed to investigate the fate of nitrite under different oxidation (0.1-1.5 mgL(-1) of dissolved oxygen) and reduction conditions. High levels of reducing power were provided by allowing the cells to build up to 2.5 mM of PHB. Nitrite added was preferentially oxidised to nitrate rather than reduced even when dissolved oxygen was low and reducing power (PHB) was excessively high. However, the presence of ammonium enabled significant reduction of nitrite under low oxygen conditions. This is consistent with previous observations in SBR where aerobic nitrite and nitrate reduction occurred only as long as ammonium was present. As soon as ammonium was depleted, the rate of denitrification decreased significantly. The significance of the observed strongly stimulating effect of ammonium on nitrite reduction under SND conditions is discussed and potential consequences for SBR operation are suggested.     

Water quality before and after dam building on a heavily polluted river in semi‐arid Algeria

The impact of the construction and management of a reservoir on a polluted stream in a semi‐arid region has been highlighted using physico‐chemical indicators. The Tafna river (Algeria) collects heavily polluted wastewater from the town of Maghnia and from several factories. Organic pollution comes from domestic sewage and from food industries. Ore treatment industries discharge very acidic wastewater. Temperature, pH, conductivity, chloride, dissolved oxygen, biological oxygen demand (BOD), and nitrogen compounds have been surveyed between 1996 and 2001, before and after the construction of the dam. The change in each parameter is compared between sites located upstream and downstream from the dam. The spatio‐temporal evolution of the organic pollution indicators was highlighted by ANOVA and principal component analysis. By enhancing sedimentation of the organic matter, the reservoir makes possible a significant decline in the BOD downstream of the dam, but increases NH₄ concentration at the downstream sites. The pollution is diluted during high flows and dam releases. Conversely, during low flow periods, mineralization of organic matter is higher in the lower Tafna. Copyright © 2004 John Wiley & Sons, Ltd.     

Wave exposure and hydrologic connectivity create diversity in habitat and zooplankton assemblages at nearshore Long Point Bay,Lake Erie

During an 11-day period in August 2008, we visited 102 sites along the nearshore (~ 60 km) of Long Point Bay. The purpose of our study was to evaluate the effects of wave exposure and hydrologic connectivity on zooplankton distributions. Long Point is located within the UNESCO Long Point Biosphere Reserve (26,250 ha) and encompasses the largest wetland complex in the Great Lakes system. We sampled for zooplankton, aquatic vegetation, temperature, specific conductance, pH, dissolved oxygen, dissolved organic carbon, water clarity, total nitrogen and depth. We evaluated the impacts of exposure using wind and fetch data to calculate a Relative Exposure Index (REI). Ordination techniques revealed a large variation in physical disturbance, water clarity, nutrient concentrations, water chemistry and aquatic vegetation that explained the distribution pattern of zooplankton at the 102 sites. Gradients of REI are strongly positively correlated with environmental variables, such as pH, dissolved oxygen and temperature and highly negatively correlated with conductivity and dissolved organic carbon. Visual inspection of the ordination site scores revealed the 102 sites clustering into six main groups based on spatial location and degree of surface-water connectivity to Long Point Bay. Sheltered sites (low REI) have much higher abundance of zooplankton whereas sites that have high REI scores are characterized by relatively low zooplankton abundance with a high prevalence of Polyarthra sp. This is the largest study on the distribution pattern of zooplankton in Long Point Bay, and it highlights the importance of wave exposure and hydrologic connectivity in structuring the zooplankton community.     

Simultaneous domestic wastewater treatment and renewable energy production using microbial fuel cells (MFCs)

Microbial fuel cells (MFCS) can be used in wastewater treatment and to simultaneously produce electricity (renewable energy). MFC technology has already been applied successfully in lab-scale studies to treat domestic wastewater, focussing on organic matter removal and energy production. However, domestic wastewater also contains nitrogen that needs to be treated before being discharged. The goal of this paper is to assess simultaneous domestic wastewater treatment and energy production using an air-cathode MFC, paying special attention to nitrogen compound transformations. An air-cathode MFC was designed and run treating 1.39 L d(-1) of wastewater with an organic load rate of 7.2 kg COD m(-3) d(-1) (80% removal efficiency) and producing 1.42 W m(-3). In terms of nitrogen transformations, the study demonstrates that two different processes took place in the MFC: physical-chemical and biological. Nitrogen loss was observed increasing in line with the power produced. A low level of oxygen was present in the anodic compartment, and ammonium was oxidised to nitrite and nitrate.     

Effect of pH on nitrate and selenate reduction in flue gas desulfurization brine using the H2-based membrane biofilm reactor (MBfR)

Increased tightening of air regulations is leading more electric utilities to install flue gas desulfurization (FGD) systems. These systems produce brine containing high concentrations of nitrate, nitrite, and selenate which must be removed before discharge. The H2-based membrane biofilm reactor (MBfR) was shown to consistently remove nitrate, nitrite, and selenate at high efficiencies. The maximum selenate removal flux reached 362 mgSe m(-2)d(-1) and was higher than that observed in earlier research, which shows continual improvement of the biofilm for selenate reduction. A low pH of 6.8 inhibited precipitation when treating actual FGD brine, yet did not inhibit removal. SO4(2-) was not removed and therefore did not compete with nitrate, nitrite, and selenate reduction for the available H2.     

天然水体氮自净过程及硝化所需溶解氧源试验验证

通过试验验证了天然水体中确实存在氮的自然净化过程和同步硝化/反硝化途径。在氮与有机物浓度较低时,遮光阻断藻类光合作用试验表明,大气复氧足以使试验水质条件下的氮和有机物完全氧化。然而,有机物过早消耗对硝化后产生的硝酸氮再行反硝化作用不利。反硝化反应彻底进行可以通过外加碳源方式实现。COD初始浓度较高会引起异养菌对氧的大量消耗,使本来数量就处于劣势的硝化细菌的硝化反应受阻。     

氮元素降解随流速的变化规律研究

本文介绍了采用循环环境水槽试验对流速对氮元素降解过程的影响进行的研究。研究中,分别监测了不同流速条件下水体的氨氮、硝酸盐(NO_3~--N)、亚硝酸盐(NO_2~--N)浓度随时间的变化过程,并分析了pH随流速变化对氮元素主要降解过程的影响。结果表明:实验水体pH主要受氮元素迁移转化的影响,其值的变化与氨氮、硝酸盐(NO_3~--N)、亚硝酸盐(NO_2~--N)的浓度变化显著性相关,其与流速同样关系紧密,无论是氨化反应占主导阶段,还是硝化、反硝化反应占主导的阶段,均是流速越大,pH越高。     

Factors affecting nitrogen removal by nitritation/denitritation.

Nitrogen removal from wastewater with high nitrogen concentration and low COD/N ratio via nitrite is advantageous. The specific character of the sludge liquor enables the application of such a method. The factors affecting process efficiency were studied. From the factors followed pH, NH4+/NH3 and NO2-/HNO2 concentration and distribution seem to be most important, using sequencing batch reactor technology and treating wastewater with high NH4+ concentration (above 1 g/l). The efficient oxidation of N-NH4+ to nitrite was achieved at a minimal nitrate production. Primary sludge was used as an internal source of substrate for the denitritation because of the organic substrate deficiency of the sludge liquor. The denitritation can be controlled by dosing of the primary sludge and can be complete. There are two operational alternatives of sludge liquor pretreatment: without pH control--lower operational costs and N-removal up to 65% and with pH control--higher operational costs and N-removal close to complete.