Michael S. Switzenbaum

Monitoring of the anaerobic methane fermentation process.

The anaerobic methane fermentation process is being used more frequently for the treatment of liquid wastes. This is primarily due to the newer technologies that are able to realize the advantages of anaerobic treatment while minimizing the detriments. One obstacle remaining that would further increase the usage of these processes involves the need to monitor the process. Traditional indicators are adequate for gradual changes and for detecting process upsets once they are underway. However, the newer technologies are high-rate systems, and for these systems, shock overloads and toxic doses require prompt corrective responses in order to avoid process failure. Thus, along with the newer technologies have come new process indicators for monitoring the anaerobic methane fermentation process. An ideal indicator would be one that is easy to measure, related to the current metabolic status of the system, and perhaps available for on-line measurement. This paper will review the indicators that have been proposed for monitoring the anaerobic processes.

The effect of heavy metals on methane production and hydrogen and carbon monoxide levels during batch anaerobic sludge digestion

Abstract Heavy metals can cause upset in the anaerobic digestion of municipal sludges. Using serum bottle assays, the impact of three transition heavy metals—copper, zinc and cadmium on methane production rate and trace hydrogen and carbon monoxide gas levels during the digestion of waste activated sludge was examined. Results indicate that normal substrate flow is interrupted at a point in the degradation sequence prior to the methanogenic steps by the pulse addition of heavy metals. Substrate pulsing experiments were used to help assess which groups of the anaerobic ecosystem were inhibited by heavy metal addition. Results indicate hydrogen monitoring holds promise to be an effective means to examine digester upset brought on as a consequence of heavy metal induced inhibition. Results also demonstrate the need to supplement pure and enrichment culture studies with assays that examine the response of the entire ecosystem of interest. A characteristic CO response was also observed and may be useful in detecting metal induced inhibition.

Best management practices for airport deicing stormwater

With the advent of new regulations concerning aircraft deicing and management of spent aircraft deicing fluids (ADFs), many airports now face the dual challenges of simultaneously maintaining public safety and protecting the environment. This paper provides a theoretical assessment of the potential environmental impact of stormwater runoff and offers detailed current information on alternative deicing fluid application methods and materials, collection and treatment practices.

Anaerobic expanded bed treatment of whey

Abstract Anaerobic treatment of cheese whey offers the dual advantages of energy production and pollution control. Based on the results of a survey among cheese producers in New York State it is shown that up to 46% of the oil and gas needs of a cheese plant could be supplied by methane generated from the by-product whey. This paper also presents the results of a feasibility study with the anaerobic attached film expanded-bed reactor treating whey. It is shown that efficient treatment of whey is possible at low retention times and at high organic loading rates.

Anaerobic fixed film wastewater treatment

Abstract The anaerobic methane fermentation process has long been used in the field of wastewater engineering in sludge processing, mainly for waste stabilization and solids reduction. Recently, major advances in the fundamental understanding of the process microbiology and biochemistry, along with the development of new reactor configurations have promoted a resurgence of interest in the use of this technology for the processing of liquid industrial and municipal wastewaters. Three of these new processes, the anaerobic filter, expanded/fluidized bed, and upflow anaerobic sludge blanket, are discussed. Each of these processes is a fixed film process, which enables the attainment of high solids retention times for good system efficiency and stability, with low hydraulic retention times for system economy. Fixed film anaerobic processes are able to realize many of the benefits of anaerobic processes while overcoming many of the problems historically associated with anaerobic processes. Each of the processes is described, and examples are presented for industrial and municipal applications. Finally, the processes are qualitatively compared. At present, it is not possible to say which reactor configuration is best. In fact, the selection is often dependent on wastewater characteristics, local factors, and several other factors. More full-scale data and operating experience along with basic research needs are needed to clarify further this situation, and to design these systems optimally.

The effects of organic toxicants on methane production and hydrogen gas levels during the anaerobic digestion of waste activated sludge

Abstract Batch serum bottle assays were conducted to examine the response of the anaerobic digestion process to inhibition induced by the pulse addition of four organic toxicants [chloroform, bromoethanesulfonic acid (BES), trichloroacetic acid (TCAA) and formaldehyde]. The impact that increasing levels of inhibition of methane production had on hydrogen response and volatile fatty acid (VFA) accumulation were examined. All of the toxicants, with the exception of formaldehyde, appeared to elicit similar hydrogen response patterns and VFA accumulations for similar levels of inhibition. Results indicate that both the hydrogen and acetate catabolizing methanogenic populations were inhibited to approximately the same extent by chloroform, BES, and TCAA. Severe inhibition of methane production (>70% reduction of methane produced compared to controls) resulted in a rapid accumulation of hydrogen in the gaseous headspace. When inhibition was less severe, hydrogen accumulated to levels only slightly above controls. Based on these preliminary results, there appears to be some limits on the potential of using hydrogen as an early warning indicator of process upset. Results do indicate, however, that monitoring hydrogen in consert with conventional process indicators should improve digester monitoring and may provide more rapid indication of process upsets due to toxic shocks.

Obstacles in the implementation of anaerobic treatment technology

Abstract The anaerobic methane fermentation process is able to be used for a wide variety of applications. These applications are in various stages of development — from proven technologies to developing technologies. Municipal and industrial wastewater treatment fall in between these extremes; they are developed, but not fully proven. This paper concentrates on these two applications in terms of obstacles to their full implementation. While much progress has been made in the use of anaerobic treatment for municipal and industrial wastewater treatment, the development and implementation has not been as quick as was expected by numerous researchers and practitioners. Possible reasons for this delay are discussed. Perhaps the most significant obstacle is lack of experience with the process. In reviewing the history and subsequent development of sanitary engineering, it can be seen that engineering practice often has to run ahead of basic science to resolve sanitation challenges. Because of this, there is often a long lag time between the implementation of technology and a rational design procedure for that technology. Rational design procedures are needed to build and operate reliable, economic, wastewater treatment processes. This assures credibility for the engineers and the operators of such technologies. Rational design must depend on both advances in basic science as well as accumulated operating experience and, ultimately, this takes time.

Characterization of compost biofiltration media

The effect of compost quality on performance of biofiltration media was investigated. Three types of compost media were characterized in terms of their key properties, including pH, total organic carbon (TOC) and nitrogen, moisture content, oxygen uptake rates and heterotrophic and fungal plate counts. Laboratory-scale biofilter columns were each filled with a different compost medium mixed with buffer and a bulking agent. The columns were operated with a volatile organic compound (VOC) mixture consisting of ethyl alcohol, butyraldehyde, ethyl acetate, and 1,1-diethoxybutane and subjected to various operating conditions. After 13 months, the columns were sampled and post-characterization of the media was performed. A mixture of biosolids/horse manure compost, which had a high initial microbial activity, had the shortest acclimation period. Best overall performance, however, was observed with yard waste compost, which was the most stable medium. Media hydrophobicity was a key factor in long-term performance. Significant changes in compost structure, moisture content, pH, volatile solids, oxygen uptake rates, and microbial population densities were observed over the course of the study. Analyses of organic nitrogen content showed that significant amounts of nitrogen were not depleted from the media.

Analysis of anaerobic biofilms

Abstract Biofilms from anaerobic fixed film reactors (anaerobic filter, upflow anaerobic sludge blanket, and anaerobic fluidized bed) developed under identical experimental conditions, were characterized in terms of chemical, microbiological, and morphological composition. Using Scanning Electron Microscopy (SEM), the nature of the biofilms are described. Factor 420 analysis showed the fluidized bed to have the highest level of the coenzyme. However, factor 420 levels were not related to COD removal or gas production. Large amounts of inorganic matter were found in each of the biofilms.

Initial anaerobic biofilm development

SummaryThe initial rate of methanogen accumulation and anaerobic biofilm accumulation increased with increasing bulk liquid organic space loading and volatile suspended solids concentration. The rates were faster at a 15 day bulk liquid SRT than 5 day SRT. The results indicate that a reduction in start-up time for anaerobic fixed film reactors might be achieved by maintaining high organic space loadings and high concentrations of active microorganisms in the bulk liquid phase during the start-up period.