Tequila vinasses: generation and full scale treatment processes

The production of Tequila (55% Alc. Vol.) in Mexico for the year 2008 was 227 million liters, and consequently around 2,270 million liters of Tequila vinasses (TVs) were generated, which without proper treatment is equivalent to the pollution produced by 6.2 million people. The lack of both finances and technology availability are reasons for the absence of wastewater treatment plants (WTP) in the Tequila factories, with the exception of some big and medium size factories. There are WTPs based on both biological and physicochemical processes and also combinations of them that have been implemented to treat TVs; however, in most of the cases the implementation has not been effective. The WTPs that utilize a biological anaerobic process seem to be the most suitable for the treatment of TVs; however, there are some technical factors that have to be considered before the implementation of a technological solution for this environmental issue. This mini-review presents the state of the art of wastewater treatments performance in the Tequila industry, discussing the efficacy of the systems together with other technologies that could be considered to fulfill the requirements for the environmental regulation in Mexico.     

Fault detection filter design for an anaerobic digestion process

In this paper, a Fault Detection and Isolation observer based method has been applied to biological wastewater treatment process. The method is designed with a dynamic model and the observer is determined using the eigenstructure assignment approach. The efficiency of the method is demonstrated for both detection and isolation of an actuator and a sensor failure using experimental data from a pilot scale anaerobic digestion process for the treatment of an industrial wine distillery vinasses.     

Azo-dye degradation in an anaerobic-aerobic treatment system operating on simulated textile effluent

 Decolorisation of azo dyes during biological effluent treatment can involve both adsorption to cell biomass and degradation by azo-bond reduction during anaerobic digestion. Degradation is expected to form aromatic amines, which may be toxic and recalcitrant to anaerobic treatment but degradable aerobically. Methods for the quantitative detection of substituted aromatic amines arising from azo-dye cleavage are complex. A simple qualitative method is suggested as a way in which to investigate whether decolorisation is actually due to degradation, and whether the amines generated are successfully removed by aerobic treatment. Samples from a combined anaerobic-aerobic system used for treating a simulated textile wastewater containing the reactive azo dye Procion Red H-E7B were analysed by high-performance liquid chromatoraphy/ultraviolet (HPLC-UV) methods. Anaerobic treatment gave significant decolorisation, and respiration-inhibition tests showed that the anaerobic effluent had an increased toxicity, suggesting azo-dye degradation. The HPLC method showed that more polar, UV-absorbing compounds had been generated. Aerobically, these compounds were removed or converted to highly polar compounds, as shown by HPLC analysis. Since the total organic nitrogen (TON) decreased aerobically as organic N-containing compounds were mineralised, aromatic amine degradation is suggested. Although only a simple qualitative HPLC method was used, colour removal, toxicity and TON removal all support its usefulness in analysing biotreatment of azo dyes. Received: 2 August 1999 / Accepted: 3 September 1999     

Regulation of the organic pollution level in anaerobic digesters by using off-line COD measurements

A sampled delayed scheme is proposed to regulate the organic pollution level in anaerobic digestion processes by using off-line COD measurements. The proposed scheme is obtained by combining an error feedback control with a steady state estimator to track constant references and attenuate process load disturbances. The controller performance is tested experimentally for the treatment of tequila vinasses over a period of 68 days under different set-point values and several uncertain scenarios which include badly known kinetic parameters and load disturbances. Experimental results show that the COD concentration can be effectively regulated under the influence of set-point changes and high load disturbances by using only a daily off-line COD measurement, which makes the industrial application of the proposed control scheme feasible.     

Anaerobic thermophilic digestion of cutting oil wastewater: Effect of co-substrate

This paper describes the thermophilic (55 °C) anaerobic biodegradation of a mixed feed composed of vinasses and cutting oil wastewater (COW) in a laboratory upflow anaerobic fixed-film reactor (UAFF) with a porous support medium. The experimental protocol was defined to examine the effect of increasing the percentage of cutting oil wastewater in the feed.The UAFF reactor was initially started-up with vinasses as the only carbon source at an organic loading rate of 22.3 kg COD/m³ day and HRT of 0.8 days using porous particles as the support (SIRAN). The percentage of organic matter composed of vinasses was subsequently reduced while increasing the amount of cutting oil until 100% of cutting oil wastewater was added in the feed. Four stages were considered in the study (0, 42.4, 66.6 and 100% COW). HRT was adjusted in order to maintain an approximately constant organic loading rate applied to the system. Under theses conditions, the UAFF reactor was subjected to a programme of steady-state operation with hydraulic retention times (HRT) in the range 0.8–0.15 days and organic loading rates (OLR) between 22.3 and 14.9 kg COD/m³ day in order to evaluate the treatment capacity of the system.The COD removal efficiency was found to be 87% COD and 94.6% TOC in the reactor when treating vinasses at 22.3 kg COD/m³ day. The volumetric methane level produced in the digester reached 0.45 m³/m³ day. After an operating period of 120 days, the reactor was fed with cutting oil wastewater (COW) as the only source of carbon. An OLR of 16.7 kg COD/m³ day was achieved with 85.8% COD removal efficiency (58.1%TOC) in the experimental UAFF reactor. Under these conditions the volumetric methane produced in the digester was negligible.Hence, COW can be removed, if not degraded, by anaerobic treatment in the presence of a biodegradable co-substrate. Wine vinasses degradation creates conditions for non-biological removal of COW constituents. More studies are necessary in order to test the mechanisms of organic removal when biodegradation apparently had ceased. Also, toxicity assays of COW are necessary to evaluate the toxicity to the methanogenic community.     

Super blue box recycling (SUBBOR) enhanced two-stage anaerobic digestion process for recycling municipal solid waste: laboratory pilot studies

The super blue box recycling (SUBBOR) process is an enhanced, multi-stage anaerobic digestion process for mixed municipal solid waste (MSW) and other biomass feedstock materials. The technology centers on enhanced high solids, thermophilic digestion after steam-pressure disruption of the ligno-cellulosic fiber components that are recalcitrant to conventional anaerobic digestion. Mixed MSW, rich in organic components but also containing inorganic materials, such as glass, aluminum and steel, as well as non-digestible plastic materials, has been laboratory pilot tested with a fully integrated process train designed to treat and recycle all of the MSW components. Methane yields from the MSW were 0.36 m3 CH4/kg volatile solids (VS) representing a 40% increase over the yield obtained from conventional single stage digestion. The secondary digestion step after steam pressure disruption also provided a 40% improvement in total solids and VS reduction. The residual organic fraction following two-stage digestion was fine in texture and was recovered as a clean peat fraction with reduced contents of heavy metal and other fugitive non-digested contaminants. Mass and energy balance determinations indicated a high degree of MSW diversion from landfill disposal (>80%) was achievable by the SUBBOR process as well as substantial net electrical and thermal energy production. Continuous long-term trials of the SUBBOR process at 25,000 tonnes/year are underway.     

Elevated methane emissions from a paddy field in southeast China occur after applying anaerobic digestion slurry

One hundred million tons of farm stalk waste and livestock and poultry excrement are used every year in China for the production of clean energy (biogas) by anaerobic digestion. Consequently, a large amount of fermented liquid is produced, and if disposed of improperly, it will result in secondary pollution. Agricultural application of this anaerobic slurry as a liquid fertilizer would reduce possible eutrophication of water sources from random slurry discharge and supply a superior organic fertilizer for farming. This study investigated the effect of applying anaerobic digestion slurry as a liquid fertilizer on the methane emitted from a paddy field. A two‐year (2008–2009) field experiment replacing chemical fertilizer with liquid fertilizer from anaerobically digested pig manure slurry was conducted in a paddy field in Yixing, Jiangsu, China. A static closed chamber method was used to measure methane fluxes over the period from June 2008 to October 2009. All fertilizer treatments increased methane emissions relative to untreated controls, with increases in methane ranging from 40–70% in 2008 to 48–84% in 2009. Paddy fields treated with anaerobically digested pig manure slurry had greater methane emissions (8–84% in 2008 and 3–26% in 2009) than those treated with chemical fertilizer. This suggests that the anaerobic digestion slurry would increase methane emission and so is unsuitable as a liquid fertilizer in paddy fields without development of cultivation practices to limit these emissions.     

Peracetic acid oxidation as an alternative pre-treatment for the anaerobic digestion of waste activated sludge

Anaerobic digestion is generally considered to be an economic and environmentally friendly technology for treating waste activated sludge, but has some limitations, such as the time it takes for the sludge to be digested and also the ineffectiveness of degrading the solids. Various pre-treatment technologies have been suggested to overcome these limitations and to improve the biogas production rate by enhancing the hydrolysis of organic matter. This paper studies the use of peracetic acid for disintegrating sludge as a pre-treatment of anaerobic digestion. It has been proved that this treatment effectively leads to a solubilisation of organic material. A maximum increase in biogas production by 21% is achieved. High dosages of PAA lead to a decrease in biogas production. This is due to the inhibition of the anaerobic micro-organisms by the high VFA-concentrations. The evolution of the various VFAs during digestion is studied and the observed trends support this hypothesis.     

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.     

Monitoring anaerobic sequential batch reactors via fractal analysis of pH time series

Efficient monitoring and control schemes are mandatory in the current operation of biological wastewater treatment plants because they must accomplish more demanding environmental policies. This fact is of particular interest in anaerobic digestion processes where the availability of accurate, inexpensive, and suitable sensors for the on‐line monitoring of key process variables remains an open problem nowadays. In particular, this problem is more challenging when dealing with batch processes where the monitoring strategy has to be performed in finite time, which limits the application of current advanced monitoring schemes as those based in the proposal of nonlinear observers (i.e., software sensors). In this article, a fractal time series analysis of pH fluctuations in an anaerobic sequential batch reactor (AnSBR) used for the treatment of tequila vinasses is presented. Results indicated that conventional on‐line pH measurements can be correlated with off‐line determined key process variables, such as COD, VFA and biogas production via some fractality indexes. Biotechnol. Bioeng. 2013; 110: 2131–2139. © 2013 Wiley Periodicals, Inc.     

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.     

Transformation and fate of 2,4,6-trinitrotoluene (TNT) in anaerobic bioslurry reactors under various aeration schemes: implications for the decontamination of soils

Energetic compounds have been used in a variety of industrial and military applications worldwide leading to widespread environmental contamination. Many of these compounds are toxic and resist degradation by oxidative enzymes resulting in a need for alternative remediation methods. It has been shown that trinitrotoluene (TNT)-contaminated soil subjected to treatment in strictly anaerobic bioreactors results in tight binding of TNT transformation products to soil organic matter. The research presented here examined the fate of TNT and its metabolites in bioreactors under three different aeration regimes. In all treatment regimes, the typical metabolites of aminodinitrotoluenes and diaminonitrotoluenes were observed prior to irreversible binding into the soil fraction of the slurry. Significant transformation of TNT into organic acids or simple diols, as others report in prior work, was not observed in any of the treatments and is an unlikely fate of TNT in anaerobic soil slurries. These results indicate that aeration does not dramatically affect transformation or fate of TNT in reactor systems that receive a rich carbon source but does affect the rate at which metabolites become tightly bound to the soil. The most rapid transformations and lowest redox potentials were observed in reactors in which an aerobic headspace was maintained suggesting that aerobes play a role in establishing conditions that are most conducive to TNT reduction.     

Comparison of static,in-vessel composting of MSW with thermophilic anaerobic digestion and combinations of the two processes

The biological stabilisation of the organic fraction of municipal solid waste (OFMSW) into a form stable enough for land application can be achieved via aerobic or anaerobic treatments. To investigate the rates of degradation (e.g. via electron equivalents removed, or via carbon emitted) of aerobic and anaerobic treatment, OFMSW samples were exposed to computer controlled laboratory-scale aerobic (static in-vessel composting), and anaerobic (thermophilic anaerobic digestion with liquor recycle) treatment individually and in combination. A comparison of the degradation rates, based on electron flow revealed that provided a suitable inoculum was used, anaerobic digestion was the faster of the two waste conversion process. In addition to faster maximum substrate oxidation rates, anaerobic digestion (followed by post-treatment aerobic maturation), when compared to static composting alone, converted a larger fraction of the organics to gaseous end-products (CO₂ and CH₄), leading to improved end-product stability and maturity, as measured by compost self-heating and root elongation tests, respectively. While not comparable to windrow and other mixed, highly aerated compost systems, our results show that in the thermophilic, in-vessel treatment investigated here, the inclusion of a anaerobic phase, rather than using composting alone, improved hydrolysis rates as well as oxidation rates and product stability. The combination of the two methods, as used in the DiCOM^® process, was also tested allowing heat generation to thermophilic operating temperature, biogas recovery and a low odour stable end-product within 19 days of operation.     

Anaerobic Codigestion of Sludge: Addition of Butcher’s Fat Waste as a Cosubstrate for Increasing Biogas Production

Fat waste discarded from butcheries was used as a cosubstrate in the anaerobic codigestion of sewage sludge (SS). The process was evaluated under mesophilic and thermophilic conditions. The codigestion was successfully attained despite some inhibitory stages initially present that had their origin in the accumulation of volatile fatty acids (VFA) and adsorption of long-chain fatty acids (LCFA). The addition of a fat waste improved digestion stability and increased biogas yields thanks to the higher organic loading rate (OLR) applied to the reactors. However, thermophilic digestion was characterized by an effluent of poor quality and high VFA content. Results from spectroscopic analysis suggested the adsorption of lipid components onto the anaerobic biomass, thus disturbing the complete degradation of substrate during the treatment. The formation of fatty aggregates in the thermophilic reactor prevented process failure by avoiding the exposure of biomass to the toxic effect of high LCFA concentrations.     

Recent advances in methane fermentation technology

In the past two decades, a number of biotechnologies for anaerobic (methanogenic) wastewater treatment have been created, and practical applications of these processes are now being extended to more recalcitrant wastewaters and to wastewaters at extreme temperatures. Our knowledge of methanogenic organic degradation associated with bioreactors is also accumulating at a rapid rate. The recent advancement of such fundamental understanding is attributed to modern molecular biology techniques applied to the study of microbial communities and to continuous challenges to the cultivation of many important but recalcitrant anaerobes in bioreactors.     

Influence of mechanical and thermochemical pretreatments on anaerobic digestion ofSpirulina maxima algal biomass

The algaSpirulina maxima was subjected to mechanical (ultrasonic + mechanical disintegration) and thermochemical pretreatments and used as a substrate in anaerobic digestion. Results indicate that the pretreatments increased the solubility of biomass and had a positive effect on acid forming bacteria. Thermochemical treatments produced compounds toxic to methanogenic bacteria especially when treatment conditions became more severe.     

Enhancement of dry anaerobic batch digestion of the organic fraction of municipal solid waste by an aerobic pretreatment step

The start-up of the dry anaerobic batch digestion by the BIOCEL-concept of the organic fraction of municipal solid waste (MSW) is unbalanced when a methanogenic inoculum (digested sewage sludge) is added to a total solids concentration of 35%. The unbalanced conditions are the result of the rapid degradation of easily-degradable compounds which are present in the organic fraction. Enhancement of the first start-up of the dry batch digestion was tried by applying an aerobic partial-composting step. By this aerobic treatment the easily degradable compounds are removed. After the composting step the anaerobic digestion will be limited by the conversion of the ligno-cellulose part of the organic fraction. It appeared that at least 19·5% of the volatile solids (VS) should be converted during the aerobic composting period before acid formation in the digestion was in balance with the methane formation. This amount of aerobically degraded VS means a 40% loss of potential biogas. The loss of a part of the biogas is a major drawback to the partial composting as a method for enhancing the start-up of the dry anaerobic digestion. A shorter composting period which is combined with another start-up method might be a feasible method to decrease the energy input of the dry digestion process.     

Development of anaerobic digestion methods for palm oil mill effluent (POME) treatment

Palm oil mill effluent (POME) is a highly polluting wastewater that pollutes the environment if discharged directly due to its high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) concentration. Anaerobic digestion has been widely used for POME treatment with large emphasis placed on capturing the methane gas released as a product of this biodegradation treatment method. The anaerobic digestion method is recognized as a clean development mechanism (CDM) under the Kyoto protocol. Certified emission reduction (CER) can be obtained by using methane gas as a renewable energy. This review aims to discuss the various anaerobic treatments of POME and factors that influence the operation of anaerobic treatment. The POME treatment at both mesophilic and thermophilic temperature ranges are also analyzed.     

THE EFFECT OF ADDED NITROGEN ON THE RATE OF DECOMPOSITION OF ORGANIC MATTER

(1) N added to decomposing organic matter often has no effect or a negative effect on microbial activity, at least in the long term. More than 60 papers are cited in support of this statement.
(2) The negative effect of N is mainly found with recalcitrant organic matter with a high C/N ratio (straw, wood, etc.), whereas a positive effect of N is common for easily degradable organic material with low C/N ratio.
(3) The negative effect of N could be explained by: (i) N disturbs the outcome of competition between potent and less potent decomposers; (ii) through 'ammonia metabolite repression', N blocks production of certain enzymes, at least in basidiomycetes, and enhances breakdown of the most available cellulose, whereby recalcitrant lignocellulose accumulates; (iii) amino compounds condense with polyphenols and other decomposition products, forming 'browning precursors' which are toxic or inhibitory.
(4) The effect of adding N may depend on the microflora present.
(5) There are indications that some microorganisms have a 'luxury uptake' of N when it is present in sufficient amounts, thereby delaying N mineralization.
(6) The addition of N seems to increase the formation of water-soluble , brown, recalcitrant compounds, but to decrease the amount of humus formed.     

Biological degradation of Ascophyllum nodosum

The alginate forms the major structural component of the cell wall and the intercellular matrix of the brown alga Ascophyllum nodosum. Successful biological degradation of A. nodosum would largely depend on the dissolution of the alginate, but reactive compounds in the alga such as polyphenols may also have toxic effects on the microbial population involved. Aerobic and anaerobic batch reactors, operated at 35°C and pH 7, were fed milled A. nodosum, nutrients and inocula adapted to seaweed degradation. The dominant factor for conversion of organic matter during anaerobic digestion was the inhibitory effect of the polyphenols on alginate lyases and methane production. Probably, the relative large fraction of high molecular weight polyphenols (>10 kDa) in this alga gave efficient binding of proteins during digestion. The anaerobic degradation was greatly stimulated when the polyphenols were fixed with low amounts of formaldehyde. An accumulated content of guluronate in the remaining alginate indicated that Ca-crosslinking also limited the guluronate lyase access to the polymer. In contrast, the aerobic digestion of alga gave no increase in the guluronate content of the residual alginate. Compared to anaerobic conditions, the phenols had a much lower influence on the hydrolytic rate of organic matter during aerobic conditions. This revised version was published online in August 2006 with corrections to the Cover Date.