堆肥化处理对畜禽粪便中四环素类抗生素及抗性基因控制的研究进展

随着四环素类抗生素在畜禽养殖中的广泛应用,畜禽粪便已成为四环素类抗生素和抗性基因的重要富集位点,其未经处理直接施用具有潜在的生态环境和人类健康风险。堆肥化处理可有效消减畜禽粪便中的四环素类抗生素,并且对抗性基因的扩散和传播具有一定的控制效果。本综述比较了不同的堆肥化工艺对粪肥中四环素类抗生素消减的效果,并重点讨论了其微生物降解机理,总结了堆肥化处理对粪肥中四环素抗性基因消减的研究进展,进一步讨论了堆肥化处理过程中抗性基因变化的微生态机理与控制策略,最后提出了采用热水解等预处理工艺去除抗生素压力和采用厌氧堆肥化工艺增强抗性基因控制的技术建议,以及从动态的角度采用高通量的检测技术来解析抗性基因消减机制的研究策略建议。     

Biological nutrients removal from the supernatant originating from the anaerobic digestion of the organic fraction of municipal solid waste

Abstract

This study critically evaluates the biological processes and techniques applied to remove nitrogen and phosphorus from the anaerobic supernatant produced from the treatment of the organic fraction of municipal solid waste (OFMSW) and from its co-digestion with other biodegradable organic waste (BOW) streams. The wide application of anaerobic digestion for the treatment of several organic waste streams results in the production of high quantities of anaerobic effluents. Such effluents are characterized by high nutrient content, because organic and particulate nitrogen and phosphorus are hydrolyzed in the anaerobic digestion process. Consequently, adequate post-treatment is required in order to comply with the existing land application and discharge legislation in the European Union countries. This may include physicochemical and biological processes, with the latter being more advantageous due to their lower cost. Nitrogen removal is accomplished through the conventional nitrification/denitrification, nitritation/denitritation and the complete autotrophic nitrogen removal process; the latter is accomplished by nitritation coupled with the anoxic ammonium oxidation process. As anaerobic digestion effluents are characterized by low COD/TKN ratio, conventional denitrification/nitrification is not an attractive option; short-cut nitrogen removal processes are more promising. Both suspended and attached growth processes have been employed to treat the anaerobic supernatant. Specifically, the sequencing batch reactor, the membrane bioreactor, the conventional activated sludge and the moving bed biofilm reactor processes have been investigated. Physicochemical phosphorus removal via struvite precipitation has been extensively examined. Enhanced biological phosphorus removal from the anaerobic supernatant can take place through the sequencing anaerobic/aerobic process. More recently, denitrifying phosphorus removal via nitrite or nitrate has been explored. The removal of phosphorus from the anaerobic supernatant of OFMSW is an interesting research topic that has not yet been explored. At the moment, standardization in the design of facilities that treat anaerobic supernatant produced from the treatment of OFMSW is still under development. To move toward this direction, it is first necessary to assess the performance of alternative treatment options. It study concentrates existing data regarding the characteristics of the anaerobic supernatant produced from the treatment of OFMSW and from their co-digestion with other BOW. This provides data documenting the effect of the anaerobic digestion operating conditions on the supernatant quality and critically evaluates alternative options for the post-treatment of the liquid fraction produced from the anaerobic digestion process.     

New concept of contaminant removal from swine wastewater by a biological treatment process

Pollution from concentrated animal feeding operations (CAFOs) are the most serious pollution source in China now, and swine wastewater contains high concentrations of nutrients such as chemical oxygen demand (COD), biochemical oxygen demand 5 (BOD5), ammonium, and emergent contaminants related to public health. Biological processes are the most popular treatment methods for COD and ammonium removal. Considering the low operation cost, easy maintenance and high removal rate of contaminants in recent years, nitrogen removal via nitrite and real-time control processes using oxidation-reduction potential (ORP) and/or pH as parameters to control the aerobic and anaerobic cycles of a system has received much attention for animal wastewater treatment. During the biological treatment process, the emergent contaminants such as estrogen, antibiotics, and disinfec-tion reagents have been the focus of research recently, and degradation bacteria and resistance bacteria have also been extracted from activated sludge. The microbial analysis technique is also advancement in the field of biodegrada-tion bacteria and resistance bacteria. All of these advance-ments in research serve to improve wastewater treatment and decrease environmental hazards, especially for using manure as a fertilizer source for crop production.     

Anaerobic degradation of adsorbable organic halides (AOX) from pulp and paper industry wastewater

Adsorbable organic halides (AOX) are generated in the pulp and paper industry during the bleaching process. These compounds are formed as a result of reaction between residual lignin from wood fibres and chlorine/chlorine compounds used for bleaching. Many of these compounds are recalcitrant and have long half-life periods. Some of them show a tendency to bioaccumulate while some are proven carcinogens and mutagens. Hence, it is necessary to remove or degrade these compounds from wastewater. Physical, chemical and electrochemical methods reported to remove AOX compounds are not economically viable. Different types of aerobic, anaerobic and combined biological treatment processes have been developed for treatment of pulp and paper industry wastewater. Maximum dechlorination is found to occur under anaerobic conditions. However, as these processes are designed specifically for reducing COD and BOD of wastewater, they do not ensure complete removal of AOX. This paper reviews the anaerobic biological treatments developed for pulp and paper industry wastewater and also reviews the specific micro-organisms reported to degrade AOX compounds under anaerobic conditions, their nutritional and biochemical requirements. It is imperative to consider these specific micro-organisms while designing an anaerobic treatment for efficient removal of AOX.     

New concept of contaminant removal from swine wastewater by a biological treatment process

Pollution from concentrated animal feeding operations (CAFOs) are the most serious pollution source in China now, and swine wastewater contains high concentrations of nutrients such as chemical oxygen demand (COD), biochemical oxygen demand 5 (BOD₅), ammonium, and emergent contaminants related to public health. Biological processes are the most popular treatment methods for COD and ammonium removal. Considering the low operation cost, easy maintenance and high removal rate of contaminants in recent years, nitrogen removal via nitrite and real-time control processes using oxidation-reduction potential (ORP) and/or pH as parameters to control the aerobic and anaerobic cycles of a system has received much attention for animal wastewater treatment. During the biological treatment process, the emergent contaminants such as estrogen, antibiotics, and disinfection reagents have been the focus of research recently, and degradation bacteria and resistance bacteria have also been extracted from activated sludge. The microbial analysis technique is also advancement in the field of biodegradation bacteria and resistance bacteria. All of these advancements in research serve to improve wastewater treatment and decrease environmental hazards, especially for using manure as a fertilizer source for crop production.     

Novel microbial nitrogen removal processes

The present-day wastewater treatment practices can be significantly improved through the introduction of new microbial treatment technologies. Recently, several new processes for nitrogen removal have been developed. These new nitrogen removal technologies provide practicable options for treating nitrogen-laden wastewaters. The new processes are based on partial nitrification of ammonium to nitrite combined with anaerobic ammonium oxidation. These processes include the single reactor system for high ammonia removal over nitrite (SHARON) process, which involves part conversion of ammonium to nitrite; the anaerobic ammonium oxidation (ANAMMOX) process, which involves anaerobic ammonium oxidation; and the completely autographic nitrogen removal over nitrite (CANON) process, which involves nitrogen removal within one reactor under oxygen-limited conditions. These new processes target the removal of nitrogen from wastewaters containing significant quantities of ammonium.     

限氧自养硝化-反硝化生物脱氮新技术

限氧自养硝化—反硝化是部分硝化与厌氧氨氧化相耦联的生物脱氮反应过程,通过严格控制溶解氧在0．1～0．3mg·L^-1,实现硝化反应控制在亚硝酸阶段,然后以硝化阶段剩余的NH4^+作为电子供体,在厌氧条件下实现反硝化,该反应过程是完全的自养硝化—反硝化过程,具有能耗低、脱氮效率高、反应系统占地面积小等优点,适用于处理COD／NH4^+—N低的废水,是一种非常有应用前景的生物脱氮技术,文中详细介绍了限氧自养硝化—反硝化生物脱氮反应过程的研究进展,讨论了其微生物学机理及应用前景。     

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.     

Simultaneous nitrification,denitrification, and phosphorus removal in a lab-scale sequencing batch reactor

Simultaneous nitrification and denitrification (SND) via the nitrite pathway and anaerobic-anoxic-enhanced biological phosphorus removal (EBPR) are two processes that can significantly reduce the energy and COD demand for nitrogen and phosphorus removal. The combination of these two processes has the potential of achieving simultaneous nitrogen and phosphorus removal with a minimal requirement for COD. A lab-scale sequencing batch reactor (SBR) was operated in alternating anaerobic-aerobic mode with a low dissolved oxygen (DO) concentration (0.5 mg/L) during the aerobic period, and was demonstrated to accomplish nitrification, denitrification, and phosphorus removal. Under anaerobic conditions, COD was taken up and converted to polyhydroxyalkanoates (PHAs), accompanied by phosphorus release. In the subsequent aerobic stage, PHA was oxidized and phosphorus was taken up to <0.5 mg/L by the end of the cycle. Ammonia was also oxidized during the aerobic period, but without accumulation of nitrite or nitrate in the system, indicating the occurrence of simultaneous nitrification and denitrification. However, off-gas analysis showed that the final denitrification product was mainly nitrous oxide (N(2)O), not N(2). Further experimental results demonstrated that nitrogen removal was via nitrite, not nitrate. These experiments also showed that denitrifying glycogen-accumulating organisms (DGAOs), rather than denitrifying polyphosphate-accumulating organisms (DPAOs), were responsible for the denitrification activity.     

Real-time treatment of dairy manure: implications of oxidation reduction potential regimes to nutrient management strategies

A pilot-scale sequencing batch reactor (SBR) was operated at a dairy farm to test real-time based control in winter operation conditions. A combination of high loading and low oxidation reduction potential (ORP) conditions in the aerobic stage of SBR treatment (an end value of -50 to -150 mV) inhibited nitrification while maintaining carbon removal. After a period of over-aeration over several cycles, the ORP at the end of the aerobic stage increased to values of 50-75 mV. Subsequently, nitrification was observed, accompanied by higher total cycle times. Significant increase in removal efficiencies of ammonical nitrogen (alpha<0.0001) and chemical oxygen demand (alpha<0.001) were observed for the high ORP phase. It is postulated that higher ORP regimes are needed for nitrification. In low ORP regimes, nitrification is absent or occurs at an extremely low rate. It is also noted that nitrifying systems treating high strength animal manure can possibly lead to unacceptably high levels of effluent nitrate+nitrite nitrogen (NO(x)-N). Two manure management schemes are proposed that give the farmer an option to either retain the nutrients, or remove them from the wastewater. Some advantages and disadvantages of the schemes are also discussed.     

Inhibition of chemical dose in biological phosphorus and nitrogen removal in simultaneous chemical precipitation for phosphorus removal

A study on the influence of chemical dosing on biological phosphorus and nitrogen removal was carried out through batch experimental tests by lab-scale and a full-scale wastewater treatment plant (employing a typical anaerobic-anoxic-oxic treatment). Results indicated that the inhibition of aluminum salt on biological phosphorus release and uptake processes is significant, as well as the inhibition of aluminum salt on Ammonia-Oxidizing Bacteria (AOB) is dominantly observed in the nitrification process and is recoverability. The inhibition of iron salt in biological phosphorus and nitrogen removal is weak, and only the inhibition of iron salt on phosphorus release at anaerobic periods emerge under large dosing. Evidence shows persistent inhibition from the accumulation of chemical doses in sludge mass. Intermittent chemical dosing proves recommendable for simultaneous chemical phosphorus removal.     

Three-step biological process for the treatment of the liquid fraction of cattle manure

The liquid fraction of cattle manure was subjected to a biological treatment combining anoxic-anaerobic and oxic processes in order to stabilize the organic matter and reduce nitrogen and phosphorus so as to avoid problems of pollution when applying it to the land. The anoxic process was carried out at 30 degrees C in a CSTR reactor, the anaerobic process in a UASB reactor at 37 degrees C and the oxic treatment in another CSTR at 20 degrees C. The following results were obtained when working under optimum conditions (removal efficiencies in brackets): COD was reduced from 42 to 3.8 g/L (>90%); total solids from 41 to 14 (67%); total volatile solids from 22 to 7.0 (68%); total Kjeldahl nitrogen from 2.2 to 0.1 g/L (95%); NH4(-)-N from 1.10 to 0.02 g/L (98%) and Total-Phosphorus from 0.696 to 0.058 g/L (92%). Nitrates, undetected in the liquid fraction of cattle manure, were present in the final effluent as a result of nitrification. To reduce the amount of nitrates, different recirculation rates were tested. The minimum nitrate concentration achieved was 127 mg/L using a recirculation ratio of 4.     

废水自养生物脱氮技术研究进展

基于短程硝化和厌氧氨氧化的自养脱氮工艺是生物脱氮领域研究的热点,它的发现为低碳氮比废水的处理提供了新的思路。近些年来,人们陆续开发了SHARON、ANAMMOX、CANON、OLAND等自养生物脱氮工艺,进一步推动了高效、低耗脱氮技术的开发和研究。本文从工艺原理、特点等方面,对自养生物脱氮工艺的国内外研究状况进行了总结和对比,并提出了存在的问题及发展方向。     

New concepts of microbial treatment processes for the nitrogen removal in wastewater

Many countries strive to reduce the emissions of nitrogen compounds (ammonia, nitrate, NOx) to the surface waters and the atmosphere. Since mainstream domestic wastewater treatment systems are usually already overloaded with ammonia, a dedicated nitrogen removal from concentrated secondary or industrial wastewaters is often more cost-effective than the disposal of such wastes to domestic wastewater treatment. The cost-effectiveness of separate treatment has increased dramatically in the past few years, since several processes for the biological removal of ammonia from concentrated waste streams have become available. Here, we review those processes that make use of new concepts in microbiology: partial nitrification, nitrifier denitrification and anaerobic ammonia oxidation (the anammox process). These processes target the removal of ammonia from gases, and ammonium-bicarbonate from concentrated wastewaters (i.e. sludge liquor and landfill leachate). The review addresses the microbiology, its consequences for their application, the current status regarding application, and the future developments.     

Treatment of effluents polluted by nitrogen with new biological technologies based on autotrophic nitrification-denitrification processes

In recent years, various technologies have been developed for the removal of nitrogen from wastewater that is rich in nitrogen but poor in organic carbon, such as the effluents from anaerobic digesters and from certain industries. These technologies have resulted in several patents. The core of these technologies is some of the processes and patents described in this paper: Aerobic denitrification, Sharon, Anammox, OLAND, CANON, NOx process, DEMON. More specifically, one of the first innovative options described for removing nitrogen include partial nitrification under aerobic conditions (partial Sharon process) followed by autotrophic anaerobic oxidation (Anammox process). The partial Sharon-Anammox process can be performed under alternating oxic and anoxic conditions in the same bioreactor or in two steps in two separate bioreactors. This overview focuses on the technical and biological aspects of these new types of treatment system, and compares them to other technologies. Given the fact that nitrification is a sensitive process, special attention is paid to conditions such as temperature, dissolved oxygen, hydraulic retention time, free ammonia, nitrous acid concentration, and pH. A discussion of the pros and cons of such treatment systems is also included since autotrophic nitrogen removal has advantages as well as drawbacks. The paper concludes with a discussion of future research that could improve these systems by enhancing performance and reducing costs.     

Removal of pathogen and indicator microorganisms from liquid swine manure in multi-step biological and chemical treatment

Concern has greatly increased about the potential for contamination of water, food, and air by pathogens present in manure. We evaluated pathogen reduction in liquid swine manure in a multi-stage treatment system where first the solids and liquid are separated with polymer, followed by biological nitrogen (N) removal using nitrification and denitrification, and then phosphorus (P) extraction through lime precipitation. Each step of the treatment system was analyzed for Salmonella and microbial indicators of fecal contamination (total coliforms, fecal coliforms, and enterococci). Before treatment, mean concentrations of Salmonella, total coliforms, fecal coliforms, and enterococci were 3.89, 6.79, 6.23 and 5.73 log(10) colony forming units (cfu)/ml, respectively. The flushed manure contained 10,590 mg/l TSS, 8270 mg/l COD, 688 mg/l TKN and 480 mg/l TP, which were reduced >98% by the treatment system. Results showed a consistent trend in reduction of pathogens and microbial indicators as a result of each step in the treatment system. Solid-liquid separation decreased their concentrations by 0.5-1 log(10). Additional biological N removal treatment with alternating anoxic and oxic conditions achieved a higher reduction with average removals of 2.4 log(10) for Salmonella and 4.1-4.5 log(10) for indicator microbes. Subsequent P treatment decreased concentration of Salmonella and pathogen indicators to undetectable level (<0.3 log(10) cfu/ml) due to elevated process pH (10.3). Our results indicate that nitrification/denitrification treatment after solids separation is very effective in reducing pathogens in liquid swine manure and that the phosphorus removal step via alkaline calcium precipitation produces a sanitized effluent which may be important for biosecurity reasons.     

Anaerobic filters for the treatment of coal gasification wastewater

A process train consisting of the following sequence of unit processes, a berl-saddle-packed anaerobic filter, an expanded bed, granular activated carbon anaerobic filter, and an activated sludge nitrification system was evaluated for the treatment of a synthetically prepared coal gasification wastewater. The first-stage anaerobic filter resulted in very little removal of organic matter and no methane production. Excellent reduction in organic matter occurred in the granular activated carbon anaerobic filter. The removal mechanism was initially adsorptive and near the end of the study, removal of organic matter was primarily through conversion to methane gas. It is felt that the success of the activated carbon anaerobic filter was due to the ability of the activated carbon to sequester some components of the wastewater that were toxic to the mixed culture of anaerobic microorganisms. The activated sludge nitrification system resulted in complete ammonia oxidation and was very efficient in final effluent polishing.     

Microbiology of nitrogen cycle in animal manure compost

Composting is the major technology in the treatment of animal manure and is a source of nitrous oxide, a greenhouse gas. Although the microbiological processes of both nitrification and denitrification are involved in composting, the key players in these pathways have not been well identified. Recent molecular microbiological methodologies have revealed the presence of dominant Bacillus species in the degradation of organic material or betaproteobacterial ammonia‐oxidizing bacteria on nitrification on the surface, and have also revealed the mechanism of nitrous oxide emission in this complicated process to some extent. Some bacteria, archaea or fungi still would be considered potential key players, and the contribution of some pathways, such as nitrifier denitrification or heterotrophic nitrification, might be involved in composting. This review article discusses these potential microbial players in nitrification–denitrification within the composting pile and highlights the relevant unknowns through recent activities that focus on the nitrogen cycle within the animal manure composting process.     

畜禽粪便中抗生素抗性基因的分布特征及消减技术研究进展

随着集约化畜禽养殖业的不断发展,兽用抗生素的长期使用导致畜禽粪便抗生素抗性基因污染日益严重,对生态环境和人类健康造成严重危害。如何有效消减畜禽粪便中的抗生素抗性基因成为当前研究热点。本文系统总结了畜禽粪便中抗生素抗性基因的产生途径、分布和影响因素,并阐述了好氧堆肥、厌氧消化及其强化工艺消减畜禽粪便抗生素抗性基因的研究进展,根据现有工艺研究存在的问题展望了今后的重点研究方向,为畜禽粪便中抗生素抗性基因的消减提供理论基础和技术支撑。     

Assessment of a bioaugmentation strategy with polyphosphate accumulating organisms in a nitrification/denitrification sequencing batch reactor

Different alternative configurations and strategies for the simultaneous biological removal of organic matter and nutrients (N and P) in wastewater have been proposed in the literature. This work demonstrates a new successful strategy to bring in enhanced biological phosphorus removal (EBPR) to a conventional nitrification/denitrification system by means of bioaugmentation with an enriched culture of phosphorus accumulating organisms (PAO). This strategy was tested in a sequencing batch reactor (SBR), where an 8 h configuration with 3 h anoxic, 4.5 h aerobic and 25 min of settling confirmed that nitrification, denitrification and PAO activity could be maintained for a minimum of 60 days of operation after the bioaugmentation step. The successful bioaugmentation strategy opens new possibilities for retrofitting full-scale WWTP originally designed for only nitrification/denitrification. These systems could remove P simultaneously to COD and N if they were bioaugmented with waste purge of an anaerobic/aerobic SBR operated in parallel treating part of the influent wastewater.