Simultaneous sulfide and nitrate removal in anaerobic reactor under shock loading

The performance of anaerobic reactor for simultaneous sulfide and nitrate removal under substrate shock loading was studied. The response to the shock loading could be divided into three stages i.e. disturbance, inertial and recovery periods. The effect of the shock loading was directly proportional to the intensity of the shock loads. The reactor performance was stable at a relatively lower intensity (1.5 times shock load), while it was considerably affected by higher intensity (higher than 2.0 times shock load). Nevertheless, the reactor performance recovered from disturbances at all the tested shock loads. The effluent sulfide-sulfur concentration was found as sensitive parameter, which increased up to 18 times of that at steady state; it could be used as an indicator of the reactor’s performance.     

亚硝酸盐型同步厌氧生物脱氮除硫工艺的运行性能

采用上流式厌氧污泥床(UASB)反应器研究了亚硝酸盐型同步厌氧生物脱氮除硫工艺的性能。该工艺具有很高的硫化物和亚硝酸盐转化潜能,最大容积硫化物去除率和容积硝酸盐去除率分别为13.4kg/(m3·d)和2.3kg/(m3·d);所能耐受的最大进水硫化物和亚硝酸盐浓度分别为880mg/L和252.7mg/L;最适进水硫化物和亚硝酸盐浓度分别为460mg/L和132.3mg/L,最适水力停留时间为4h。硫化物和亚硝酸盐的表观半抑制浓度分别为403.9mg/L和120.8mg/L,两者之间的联合毒性为拮抗作用。     

Process of simultaneous hydrogen sulfide removal from biogas and nitrogen removal from swine wastewater

The feasibility of a new flowchart describing simultaneous hydrogen sulfide removal from biogas and nitrogen removal from wastewater was investigated. It took 30 days for the reactor inoculated with aerobic sludge to attain a removal rate of 60% for H₂S and NO_x–N simultaneously. It took 34 and 48 days to attain the same removal rate for the reactor without inoculated sludge and the reactor inoculated with anaerobic sludge respectively. The reactor without inoculated sludge still operated successfully, despite requiring a slightly longer startup time. The packing material was capable of enhancing the removal efficiency of reactors. Based on the concentration of NO_x–N and H₂S in the effluent, the loading rate and the ability of the system to resist shock loading, the performance of the reactor filled with hollow plastic balls was greater than that of the reactor filled with elastic packing and the reactor filled with Pall rings.     

Effect of operating modes on simultaneous anaerobic sulfide and nitrate removal in microbial fuel cell

The effect of operating modes on the simultaneous sulfide and nitrate removal were studied in two-chamber microbial fuel cells (MFCs). The batch and continuous operating modes were compared and evaluated in terms of substrate removal and electricity generation. Upon gradual increase in the influent sulfide concentration from 60 to 1,020 S mg L^?1, and the hydraulic retention time decrease from 17.2 to 6 h, the MFC accomplished a good substrate removal efficiency whereby nitrogen and sulfate were the main end products. The removal efficiency of the MFC in the continuous mode was much higher than that in the batch mode, and its current densities in the continuous mode were more stable and higher than in the batch mode, which could be explained by the linear relationship between electrons released by the substrates and accepted on the electrodes. The electricity output in the continuous mode of the MFC was higher than that in the batch mode. MFC's operation in the continuous mode was a better strategy for the simultaneous treatment of sulfide and nitrate.     

Enhancing mainstream nitrogen removal by employing nitrate/nitrite-dependent anaerobic methane oxidation processes

Due to serious eutrophication in water bodies, nitrogen removal has become a critical stage for wastewater treatment plants (WWTPs) over past decades. Conventional biological nitrogen removal processes are based on nitrification and denitrification (N/DN), and are suffering from several major drawbacks, including substantial aeration consumption, high fugitive greenhouse gas emissions, a requirement for external carbon sources, excessive sludge production and low energy recovery efficiency, and thus unable to satisfy the escalating public needs. Recently, the discovery of anaerobic ammonium oxidation (anammox) bacteria has promoted an update of conventional N/DN-based processes to autotrophic nitrogen removal. However, the application of anammox to treat domestic wastewater has been hindered mainly by unsatisfactory effluent quality with nitrogen removal efficiency below 80%. The discovery of nitrate/nitrite-dependent anaerobic methane oxidation (n-DAMO) during the last decade has provided new opportunities to remove this barrier and to achieve a robust system with high-level nitrogen removal from municipal wastewater, by utilizing methane as an alternative carbon source. In the present review, opportunities and challenges for nitrate/nitrite-dependent anaerobic methane oxidation are discussed. Particularly, the prospective technologies driven by the cooperation of anammox and n-DAMO microorganisms are put forward based on previous experimental and modeling studies. Finally, a novel WWTP system acting as an energy exporter is delineated.     

Effect of sulfide on nitrate reduction in mixed methanogenic cultures

The effect of sulfide on nitrate reduction and methanogenesis was investigated in two mixed, mesophilic (35 degrees C) methanogenic cultures: sulfide-free and sulfide-acclimated (67 mg S/L total sulfide). A mixture of dextrin/peptone served as the carbon/electron donor source for the two stock cultures, as well as in all assays reported here. The sulfide-free enriched culture was amended with both nitrate (75-350 mg N/L) and sulfide (10-100 mg S/L). Denitrification was the predominant pathway at all sulfide levels tested and methanogenesis did not recover in any of the sulfide- and nitrate-amended cultures, except in the 10 mg S/L culture. Accumulation of denitrification intermediates such as NO and N(2)O took place, which irreversibly inhibited the methanogens and resulted in the complete cessation of methane production. In contrast, conversion of nitrate to nitrite and then to ammonia via dissimilatory nitrate reduction to ammonia (DNRA) prevented the accumulation of denitrification intermediates and led to the recovery of methanogenesis in the nitrate-amended, sulfide-acclimated, mixed methanogenic culture. The effect of the COD/N value on nitrate reduction was assessed with the sulfide-acclimated, methanogenic culture at COD/N values of 10, 20, and 60. As the COD/N value increased, the fraction of nitrate reduced through DNRA also increased. The results of this study have significant implications relative to the combined anaerobic treatment of carbon-, nitrogen-, and/or sulfur-bearing wastes.     

同步厌氧生物脱氮除硫工艺性能的研究

研究了同步厌氧生物脱氮除硫工艺的性能。该工艺具有很高的硫化物和硝酸盐转化潜能,稳态运行时的容积硫化物去除率和容积硝酸盐去除率分别为3.73kg/(m3.d)和0.80kg/(m3.d);能够耐受580mg/L的硫化物浓度和110mg/L的硝酸盐浓度,适宜浓度分别为280mg/L和67.5mg/L;能够耐受较高的水力负荷,适宜的水力停留时间为0.13d,反应器运行性能会因缩短水力停留时间而突发性恶化。     

Use of nitrate to control sulfide generation by sulfate-reducing bacteria associated with oily waste

Received 13 November 1998/ Accepted in revised form 03 March 1999     

Sulfide-induced dissimilatory nitrate reduction to ammonia in anaerobic freshwater sediments

Abstract: Different reduced sulfur compounds (H₂S, FeS, S₂O₃²⁻) were tested as electron donors for dissimilatory nitrate reduction in nitrate-amended sediment slurries. Only in the free sulfide-enriched slurries was nitrate appreciably reduced to ammonia (     ), with concomitant oxidation of sulfide to S⁰ (     ). The initial concentration of free sulfide appears as a factor determining the type of nitrate reduction. At extremely low concentrations of free S²⁻ (metal sulfides) nitrate was reduced via denitrification whereas at higher S²⁻ concentrations, dissimilatory nitrate reduction to ammonia (DNRA) and incomplete denitrification to gaseous nitrogen oxides took place. Sulfide inhibition of NO- and N₂O- reductases is proposed as being responsible for the driving part of the electron flow from S²⁻ to NH₄⁺.     

Modeling and experimental study on the anaerobic/aerobic/anoxic process for simultaneous nitrogen and phosphorus removal: The effect of acetate addition

A mathematical model based on the simulation software AQUASIM was developed to validate an anaerobic/aerobic/anoxic (AOA) process that enables simultaneous nitrogen and phosphorus removal in a single reactor by adding external organic carbon to preclude excess aerobic phosphate uptake by polyphosphate-accumulating organisms (PAOs) and provide phosphate for denitrifying PAOs (DNPAOs). Aerobic batch tests after anaerobic phosphate release with different chemical oxygen demand (COD) concentrations indicated that the effect of COD concentration on the phosphate uptake preclusion could be expressed by a simple formula. The reduction factor reflecting the formula, which retards the aerobic phosphate uptake in the presence of COD, was added to the process rates of aerobic polyphosphate storage and PAOs growth in the model. The improved model, which included the reduction factor, reasonably matched the experimental result regarding aerobic phosphate uptake behavior whereas the model without it did not; thus, the former precisely predicts the AOA process behavior.     

脱氮硫杆菌的脱硫特性及其处理恶臭物质硫化氢的应用

污水和污泥的处理过程中会产生大量的恶臭气体硫化氢(H2S)。脱氮硫杆菌是氧化H2S和其他硫化物的重要的脱硫工程菌。本文阐述了脱氮硫杆菌的生物学特性和氧化H2S的两种途径。分析了反应体系中的硫化物负荷、硝酸盐和亚硝酸盐的浓度、氧含量以及pH值等因素对氧化效果、反应速率、氧化途径及产物形式的影响。介绍了脱氮硫杆菌在恶臭污染治理中的应用及其在同步处理含氮含硫恶臭物质方面的发展趋势。     

Combined removal of sulfur compounds and nitrate by autotrophic denitrification in bioaugmented activated sludge system

An autotrophic denitrification process using reduced sulfur compounds (thiosulfate and sulfide) as electron donor in an activated sludge system is proposed as an efficient and cost effective alternative to conventional heterotrophic denitrification for inorganic (or with low C/N ratio) wastewaters and for simultaneous removal of sulfide or thiosulfate and nitrate. A suspended culture of sulfur-utilizing denitrifying bacteria was fast and efficiently established by bio-augmentation of activated sludge with Thiobacillus denitrificans. The stoichiometry of the process and the key factors, i.e. N/S ratio, that enable combined sulfide and nitrogen removal, were determined. An optimum N/S ratio of 1 (100% nitrate removal without nitrite formation and low thiosulfate concentrations in the effluent) has been obtained during reactor operation with thiosulfate at a nitrate loading rate (NLR) of 17.18 mmol N L(-1) d(-1). Complete nitrate and sulfide removal was achieved during reactor operation with sulfide at a NLR of 7.96 mmol N L(-1) d(-1) and at N/S ratio between 0.8 and 0.9, with oxidation of sulfide to sulfate. Complete nitrate removal while working at nitrate limiting conditions could be achieved by sulfide oxidation with low amounts of oxygen present in the influent, which kept the sulfide concentration below inhibitory levels.     

Effect of anaerobic reaction time on denitrifying phosphorus removal and N2O production

Nitrous oxide (N₂O) is a highly potent greenhouse gas; however, the characteristics of N₂O production during denitrification using poly-β-hydroxyalkanoates (PHA) as a carbon source are not well understood. In this study, effects of anaerobic reaction time (AnRT) on PHA formation, denitrifying phosphorus removal and N₂O production were investigated using a laboratory-scale anaerobic/anoxic/oxic sequencing batch reactor (An/A/O SBR). The results showed that operation of the An/A/O SBR for 0.78 SRT (47 cycles) after the AnRT was shortened from 90 min to 60 min resulted in anaerobically synthesized PHA improving by 1.8 times. This improvement was accompanied by increased phosphorus removal efficiency and denitrification. Accordingly, the N₂O-N production was reduced by 6.7 times. Parallel batch experiments were also conducted with AnRTs of 60, 90 and 120 min. All results indicated that in addition to the amount of anaerobically synthesized PHA, the kinetics of PHA degradation also regulated denitrifying phosphorus removal and N₂O production.     

Biological breakdown of denitrifying sulfide removal process in high-rate expanded granular bed reactor

This work conducted a denitrifying sulfide removal (DSR) test in an expanded granular sludge bed (EGSB) reactor at sustainable loadings of 6.09 kg m⁻³ day⁻¹ for sulfide, 3.11 kg m⁻³ day⁻¹ for nitrate–nitrogen, and 3.27 kg m⁻¹ day⁻¹ for acetate–carbon with >93% efficiency, which is significantly higher than those reported in literature. Strains Pseudomonas sp., Nitrincola sp., and Azoarcus sp. very likely yield heterotrophs. Strains Thermothrix sp. and Sulfurovum sp. are the autotrophs required for the proposed high-rate EGSB-DSR system. The EGSB-DSR reactor experienced two biological breakdowns, one at loadings of 4.87, 2.13, and 1.82 kg m⁻³ day⁻¹; reactor function was restored by increasing nitrate and acetate loadings. Another breakdown occurred at loadings of up to 8.00, 4.08, and 4.50 kg m⁻¹ day⁻¹; the heterotrophic denitrification pathway declined faster than the autotrophic pathway. The mechanism of DSR breakdown is as follows. High sulfide concentration inhibits heterotrophic denitrifiers, and the system therefore accumulates nitrite. Autotrophic denitrifiers are then inhibited by the accumulated nitrite, thereby leading to breakdown of the DSR process.     

Macroinvertebrate community traits and nitrate removal in stream sediments

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Effect of influent nutrient ratios and hydraulic retention time (HRT) on simultaneous phosphorus and nitrogen removal in a two-sludge sequencing batch reactor process

A laboratory-scale anaerobic–anoxic/nitrification sequencing batch reactor (A₂N-SBR) fed with domestic wastewater was operated to examine the effect of varying ratios of influent COD/P, COD/TN and TN/P on the nutrient removal. With the increased COD/P, the phosphorus removals exhibited an upward trend. The influent TN/P ratios had a positive linear correlation with the phosphorus removal efficiencies, mainly because nitrates act as electron acceptors for the phosphorus uptake in the A₂N-SBR. Moreover, it was found that lower COD/TN ratio, e.g. 3.5, did not significantly weaken the phosphorus removal, though the nitrogen removal first decreased greatly. The optimal phosphorus and nitrogen removals of 94% and 91%, respectively were achieved with influent COD/P and COD/TN ratios of 19.9 and 9.9, respectively. Additionally, a real-time control strategy for A₂N-SBR can be undertaken based on some characteristic points of pH, redox potential (ORP) and dissolved oxygen (DO) profiles in order to obtain the optimum hydraulic retention time (HRT) and improve the operating reliability.     

Reconsidering the use of photosynthetic bacteria for removal of sulfide from wastewater

The feasibility of using photosynthetic sulfide-oxidizing bacteria to remove sulfide from wastewater in circumstances where axenic cultures are unrealistic has been completely reconsidered on the basis of known ecophysiological data, and the principles of photobioreactor and chemical reactor engineering. This has given rise to the development of two similar treatment concepts relying on biofilms dominated by green sulfur bacteria (GSB) that develop on the exterior of transparent surfaces suspended in the wastewater. The GSB are sustained and selected for by radiant energy in the band 720-780 nm, supplied from within the transparent surface. A model of one of these concepts was constructed and with it the reactor concept was proven. The dependence of sulfide-removal rate on bulk sulfide concentration has been ascertained. The maximum net areal sulfide removal rate was 2.23 g m-(2) day-(1) at a bulk sulfide concentration of 16.5 mg L(-1) and an incident irradiance of 1.51 W m(-2). The system has a demonstrated capacity to mitigate surges in sulfide load, and appears to use much less radiant power than comparable systems. The efficacy with which this energy was used for sulfide removal was 1.47 g day(-1) W(-1). The biofilm was dominated by GSB, and evidence gathered indicated that other types of phototrophs were not present.     

潜流型菖蒲人工湿地不同C/N对污染物的去除效率

选取炉渣和砾石为基质,以无植被为对照,分别设置低、中、高浓度的3个碳水平(C1、C2、C3)和3个氮水平(N1、N2、N3)处理,研究潜流型菖蒲人工湿地在不同C/N下净化生活污水中COD、总氮(TN)、总磷(TP)的效果。结果表明,在不同C/N下,菖蒲人工湿地对污水中COD、TN的去除效果显著高于无植被的人工湿地,菖蒲植被能增加人工湿地COD去除率10.53%,增加TN去除率6.73%;而对于TP的去除,有无植被无显著差异。随着进水N、P浓度及C/N的变化,菖蒲湿地对COD、TN和TP的去除率分别为67.57%～75.85%、20.91%～56.82%和7.15%～17.78%;同时,菖蒲植株对N、P的积累量也相应的变化,其地上部的N、P积累量为4.44～14.79和1.11～3.37g.m-2,平均占湿地N、P去除率的6.91%和10.67%;地下部的N、P积累量分别为2.35～5.20和0.74～1.41g.m-2,平均占湿地N、P去除率的2.69%和6.02%。植物地上器官对湿地N、P的积累量大于地下部,有利于通过收割作用去除湿地系统中的N、P。