Concentration Of Biodegradable Organic Matter Research Articles

Assessment of Denitrification and Nitrification Processes during Landfill Leachate Treatment

Landfill leachate is generated from waste degradation in landfill sites, and its treatment includes biological or combined treatment with physico-chemical methods. A frequently applied technology in the biological stage of landfill leachate treatment plants is based on denitrification and nitrification. Nevertheless, with the availability of a huge number of scientific reports, the management of denitrification and nitrification (D/N) processes in the frame of real wastewater treatment plants (WWTPs) is rather difficult and always remains a critical technological problem. This study aims to perform a comparative assessment between denitrification and nitrification processes during landfill leachate treatment in three different situations in the WWTP of the Municipal Enterprise for Waste Treatment in Sofia City, Bulgaria. The comparative assessment is based on the biotransformation effectiveness of ammonium ions in the course of nitrification and of nitrates in the course of denitrification. Mixed samples (wastewater and activated sludge) were taken from the sequencing batch reactors operating in the mode of denitrification and nitrification. All physico-chemical (pH, dissolved oxygen, organics concentration, BOD5:COD, nitrogen and phosphorous) and biological (sludge volume index, sludge biotic index, quantity of aerobic heterotrophs, denitrifiers and nitrifiers, total dehydrogenase activity) indicators were investigated in the samples from the biobasins in the mode of denitrification and nitrification. The conditions for the implementation of the two processes were compared, along with the state of the activated sludge in the different reactors. The obtained results showed that denitrification was the critical process in the technology on the base of D/N. A major factor that managed the denitrification was the lower concentration of biodegradable organic matter which led to a deformation of the activated sludge structure, a decrease in the count of heterotrophic microorganisms, a decrease in the total activity of the activated sludge and an inhibition of the nitrate reductase activity. The nitrification processes were accomplished with high intensity. The results confirmed that D/N could be optimized and controlled using specific wastewater treatment technology parameters and purposely applied indicators.

Machine learning estimation of biodegradable organic matter concentrations in municipal wastewater

This study investigates whether a novel estimation method based on machine learning can feasibly predict the readily biodegradable chemical oxygen demand (RB-COD) and slowly biodegradable COD (SB-COD) in municipal wastewater from the oxidation–reduction potential (ORP) data of anoxic batch experiments. Anoxic batch experiments were conducted with highly mixed liquor volatile suspended solids under different RB-COD and SB-COD conditions. As the RB-COD increased, the ORP breakpoint appeared earlier, and fermentation occurred in the interior of the activated sludge, even under anoxic conditions. Therefore, the ORP decline rates before and after the breakpoint were significantly correlated with the RB-COD and SB-COD, respectively (p < 0.05). The two biodegradable CODs were estimated separately using six machine learning models: an artificial neural network (ANN), support vector regression (SVR), an ANN-based AdaBoost, a SVR-based AdaBoost, decision tree, and random forest. Against the ORP dataset, the RB-COD and SB-COD estimation correlation coefficients of SVR-based AdaBoost were 0.96 and 0.88, respectively. To identify which ORP data are useful for estimations, the ORP decline rates before and after the breakpoint were separately input as datasets to the estimation methods. All six machine learning models successfully estimated the two biodegradable CODs simultaneously with accuracies of ≥0.80 from only ORP time-series data. Sensitivity analysis using the Shapley additive explanation method demonstrated that the ORP decline rates before and after the breakpoint obviously contributed to the estimation of RB-COD and SB-COD, respectively, indicating that acquiring the ORP data with various decline rates before and after the breakpoint improved the estimations of RB-COD and SB-COD, respectively. This novel estimation method for RB-COD and SB-COD can assist the rapid control of biological wastewater treatment when the biodegradable organic matter concentration dynamically changes in influent wastewater.

Low biological phosphorus removal from effluents treated by slow sand filters.

The legislation for environment protection requires strict controls of the wastewater releasing in water bodies. The wastewater treatment plants (WWTP) have been used for organic matter degradation; however, the residual total phosphorus (TP) removal has not been efficient. TP and nitrogen present in wastewater are associated to eutrophication of water bodies and algae growth. Therefore, this study discusses the efficiency of phosphorus removal by a slow filter (SF), complementary to a WWTP and the microbial community involved. The results showed that the use of SF, with or without macrophytes, is not suitable to remove TP. Spatial variation in microbial communities distributed in three distinct zones was identified in the SF. Proteobacteria, Bacteroidetes, Chloroflexi and Firmicutes covered the hydrolytic and fermentative bacteria. The acetogenesis, nitrification, and denitrification, as well as the removal of phosphorus from the effluent, were performed by representatives affiliated to different groups. Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria among these, Dokdonella sp., Frateuria sp., Comamonas sp., Diaphorobacter sp., Nitrosospira sp., Ferruginibacter sp., Flavobacterium sp., and the uncultured OD1 were the most abundant bacteria in the SF. The low efficiency for TP removing from SF effluents can be explained by the low abundance of phosphorus accumulating organisms (PAOs), with the association of the low concentration of biodegradable organic matter in the inlet effluent. Therefore, the alternative to using SF as a complement to WWTPs, as recommended by some Brazilian environmental agencies, did not prove to be viable and new approaches must be evaluated. KEY POINTS: • The phosphorus removal was performed by a slow filter system in a WWTP but obtained a low efficiency. • Microbial spatial variation was distributed into distinct zones from slow filter. • Low abundance of PAOs was observed due to the low availability of organic matter.

EFFECT OF MOLASSES ADDITION AS BIODEGRADABLE MATERIAL ON PHENOL REMOVAL UNDER ANAEROBIC CONDITIONS

The link between the concentration of biodegradable organic matter and the rate of phenol removal in anaerobic conditions was examined in this work. This study was undertaken using a laboratory scale anaerobic stabilization pond and five closed reactors at two retention times, 2 and 5 days. The initial concentration of phenol and soluble COD decreased in the anaerobic pond effluent and the reactors with increasing hydraulic retention time; 98.6 % phenol removal was observed in reactors after 50 days and in the presence of 1000 mg/L COD, while 98.8 % removal was obtained after 5 days in the anaerobic stabilization pond system in the presence of 500 mg/L COD. Two-way ANOVA test with Scheffe post-hoc confirmed that phenol removal was optimal for 1000-2000 mg/L biodegradable COD and 50 days retention time in the reactors and with 500 mg/L biodegradable COD and 5 days retention time in the anaerobic pond.

Biological nutrient removal from leachate using a pilot liquid–solid circulating fluidized bed bioreactor (LSCFB)

Biological treatment of landfill leachate is a concern due to toxicity, high ammonia, low biodegradable organic matter concentrations, and low carbon-to-nitrogen ratio. To study the reliability and commercial viability of leachate treatment using an integrated liquid–solid circulating fluidized bed bioreactor (LSCFB), a pilot-scale LSCFB was established at the Adelaide Pollution Control Plant, London, Ontario, Canada. Anoxic and aerobic columns were used to optimize carbon and nutrient removal capability from leachate using 600 μm lava rock with a total porosity of 61%, at empty bed contact times (EBCTs) of 0.55, 0.49, and 0.41 d. The LSCFB achieved COD, nitrogen, and phosphorus removal efficiencies of 85%, 80%, and 70%, respectively at a low carbon-to-nitrogen ratio of 3:1 and nutrients loading rates of 2.15 kg COD/(m 3 d), 0.70 kg N/(m 3 d), and 0.014 kg P/(m 3 d), as compared with 60–77% COD and 70–79% nitrogen removal efficiencies achieved by upflow anaerobic sludge blanket (UASB) and moving bed bioreactor (MBBR), respectively. The LSCFB effluent characterized by ≤35 mg SBOD/L, <35 mg NH 4-N/L, <1.0 mg PO 4-P/L, and 37 mg VSS/L can easily meet sewer by-law requirements. Remarkably low yields of 0.13, 0.15, and 0.16 g VSS/g COD were observed at long biological solids retention times (SRTs) of 31, 38 and 44 d.

Nitrogen removal from landfill leachate using the SBR technology

Landfill leachate is a concern in the wastewater field due to its toxicity, high ammonium and low biodegradable organic matter concentrations. The aim of this paper is to study the reliability of landfill leachate treatment using Sequencing Batch Reactor (SBR) technology for biological nitrogen removal. During the study the SBR pilot plant treated successfully 0.48 kg N·m−3 d−1 of urban landfill leachate. Furthermore, high nitrogen removal efficiencies (80%, on average) have been achieved by the operational conditions applied (step‐feed strategy and alternating anoxic‐aerobic conditions).

Detection of Escherichia coli in Biofilms from Pipe Samples and Coupons in Drinking Water Distribution Networks

Fluorescence in situ hybridization (FISH) was used for direct detection of Escherichia coli on pipe surfaces and coupons in drinking water distribution networks. Old cast iron main pipes were removed from water distribution networks in France, England, Portugal, and Latvia, and E. coli was analyzed in the biofilm. In addition, 44 flat coupons made of cast iron, polyvinyl chloride, or stainless steel were placed into and continuously exposed to water on 15 locations of 6 distribution networks in France and Latvia and examined after 1 to 6 months exposure to the drinking water. In order to increase the signal intensity, a peptide nucleic acid (PNA) 15-mer probe was used in the FISH screening for the presence or absence of E. coli on the surface of pipes and coupons, thus reducing occasional problems of autofluorescence and low fluorescence of the labeled bacteria. For comparison, cells were removed from the surfaces and examined with culture-based or enzymatic (detection of beta-d-glucuronidase) methods. An additional verification was made by using PCR. Culture method indicated presence of E. coli in one of five pipes, whereas all pipes were positive with the FISH methods. E. coli was detected in 56% of the coupons using PNA FISH, but no E. coli was detected using culture or enzymatic methods. PCR analyses confirmed the presence of E. coli in samples that were negative according to culture-based and enzymatic methods. The viability of E. coli cells in the samples was demonstrated by the cell elongation after resuscitation in low-nutrient medium supplemented with pipemidic acid, suggesting that the cells were present in an active but nonculturable state, unable to grow on agar media. E. coli contributed to ca. 0.001 to 0.1% of the total bacterial number in the samples. The presence and number of E. coli did not correlate with any of physical and/or chemical characteristic of the drinking water (e.g., temperature, chlorine, or biodegradable organic matter concentration). We show here that E. coli is present in the biofilms of drinking water networks in Europe. Some of the cells are metabolically active but are often not detected due to limitations of traditionally used culture-based methods, indicating that biofilm should be considered as a reservoir that must be investigated further in order to evaluate the risk for human health.

A kinetic analysis of solid waste composting at optimal conditions

This discussion explores the possibility of having a measure of the biodegradable organic carbon content in solid wastes. Currently, indirect measures for determining the concentration of biodegradable organic matter are being used and most of them are based on respiration indices (oxygen consumption or carbon dioxide production) or chemical parameters (volatile solids or total organic carbon). The results obtained for the cumulative carbon dioxide production in composting experiments can be expressed as “aerobic biodegradable carbon” for the wastes that were studied. The calculation of a useful biodegradable C/N can also be obtained from the aerobic biodegradable carbon content. A comparison with some results obtained in measuring the concentration of “anaerobic biodegradable carbon” also is presented.

Organic compounds in re-circulated leachates of aerobic biological treated municipal solid waste

Biodegradation of organic matter is required to reduce the potential of municipal solid waste for producing gaseous emissions and leaching contaminants. Therefore, we studied leachates of an aerobic-treated waste from municipal solids and a sewage sludge mixture that were re-circulated to decrease the concentration of biodegradable organic matter in laboratory-scale reactors. After 12 months, the total organic C and biological and chemical oxygen demands were reduced, indicating the biodegradation of organic compounds in the leachates. Curie-point pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and pyrolysis-field ionization mass spectrometry (Py-FIMS) revealed that phenols, alkylaromatic compounds, N-containing compounds and carbohydrates were the predominate compounds in the leachates and solid waste. Leachate re-circulation led to a higher thermal stability of the residual organic matter as indicated by temperature-resolved Py-FIMS. Admixture of sewage sludge to solid waste was less effective in removing organic compounds from the leachates. It resulted in drastic higher and more bio-resistant loads of organic matter in the leachates and revealed increased proportions of alkylaromatic compounds. The biodegradation of organic matter in leachates, re-circulated through municipal solid waste, offers the potential for improved aerobic waste treatments and should be investigated on a larger scale.

A colony count model for the control of drinking water distribution systems

The purpose of this study is to select a process control parameter for monitoring microbial regrowth in a network and to develop a more accurate and relevant quality control of supply water. Two parameters were examined as potential process control parameters: the water residence time in the network and the concentration of biodegradable organic matter. Residence time calculations were carried out and validated by tracer studies in a branched network and then in a simply looped network. The measurement of the natural dissolved organic carbon (DOC) consumption in the network was preferred to the determination of any in vitro biodegradation. The measurement of consumption requires the determination of DOC in treated water and in supply water. It is simpler and less expensive than other biodegradable organic matter determinations. A model for colony counts as a function of the residence time was developed in order to demonstrate that this parameter can be used for process controlling. This model was very well adjusted to data collected in a network in winter, spring and summer. This process control parameter was then used in order to locate and estimate the quantity of water whose colony counts exceed the European directive guide level. Accurate correlation measurements between colony counts and DOC consumed in the network were carried out in three distinct systems. No significant correlations were measured. For these three networks, biodegradable organic matter measurements based on DOC determinations were demonstrated to be unreliable process control parameters for monitoring bacterial regrowth.

Evaluation of biodegradability of NOM after ozonation

The major purpose of this study was to develop a simple procedure to describe the kinetics of biodegradation of natural organic matter (NOM) in drinking water and to use this procedure to evaluate changes in the concentration of biodegradable organic matter during ozonation and biotreatment. The proposed approach quantitatively describes the formation and removal of rapidly and slowly biodegradable fractions of NOM. This study showed that, depending on source water, ozonation of NOM may result in either minimal formation of biodegradable organic carbon (BDOC), or the formation of predominantly rapidly biodegradable NOM, or in the formation of both rapidly and slowly biodegradable NOM. The kinetic data obtained in this study suggest that while conventional biofiltration processes are capable of removing the rapidly biodegradable fraction, slowly biodegradable organic matter would remain in the filter effluent and may cause bacterial regrowth in the distribution system. An addition of a small amount of easily biodegradable carbon (“stimulated” biodegradation) to ozonated water appears to be effective for the removal of slowly biodegradable organic matter.

Pollution abatement and environmental preservation

In the recent years there has been a growing concern over the problem of municipal and industrial waste disposal. In India city sewage, distilleries, tanneries, breweries, sugar mill and food processing units are the major source of organic pollution in water resources. Our growing concern about the availability of clean environment/water makes us more conscious to develop effective and beneficial treatment technologies for the liquid wastes. Anaerobic treatment of liquid waste, having high concentration of biodegradable organic matter, is a competent method to overcome this problem. With the aid of anaerobic treatment technology such wastes can be used to extract some useful products/by products and energy, like-biogas. Biogas is a clean and effective substitute of other conventional energy sources, i.e. coal. The paper highlights major issues of anaerobic treatment along-with the cost economics.&#x0D;

Change of bacterial water quality in drinking water distribution systems working with or without low chlorine residual

Investigations into distribution systems (DS) working without or with low disinfectant residuals showed that the main process for the bacteria change in such systems is the release of bacteria from the biofilm, whereas the growth of bacteria in the water can be neglected. Important for the quality are short-term increases of bacteria release connected to an increase of bacteria growth on the inner pipe surface as a result of changes in the concentration of biodegradable organic matter (BOM) in the water. A model to describe the bacterial water quality change was developed on the basis of investigations. In contrast to other models, a consideration of the formation of BOM as a result of NOM oxidation by disinfectant residuals as well as the decreasing effect of inactivation of released bacteria by the decreasing disinfectant residual concentration, were necessary.

Removal of Easily Biodegradable Organic Compounds by Drinking Water Biofilms: Analysis of Kinetics and Mass Transfer

This paper evaluates the rate of utilization of easily biodegradable organic compounds by drinking water biofilms. Tap water, which had been filtered through biologically active granular activated carbon, was used as an innoculum for biofilm growth in annular reactors (ARs). Synthetic cocktails of easily biodegradable material in the concentration range of 50–2000 mg C/m 3 were used as substrate for biofilm growth. Influent and effluent aggregate concentrations of biodegradable organic matter (BOM) were calculated by adding the measurable BOM components on a mass carbon basis. The aggregate BOM values were used for calculating the observed Damköhler number and Theile modulus (based on a reaction rate per unit surface area), which were used to determine whether external or internal mass transfer limited BOM removal. For all of the experimental trials, it was shown that neither external nor internal mass transfer limited BOM removal. Because the biofilms in this research are thin and the fact that mass transfer is not limiting, it was assumed that the bulk BOM concentration was approximately equal to the average BOM concentration in the biofilm. A linear model was obtained for the aggregate BOM flux and the product of the effluent BOM concentration and the biofilm density. The slope or the areal biodegradation rate ( k a) for the aggregate BOM was 0.033 m/h, as determined through a linear regression.

10] Biodegradable organic matter measurement and bacterial regrowth in potable water

Publisher Summary This chapter presents the methods available to evaluate biodegradable organic matter concentrations in water, and describes and compares several bioassays commonly used in the drinking water field to assess the bacterial regrowth potential of waters. Because a high biodegradable organic matter (BOM) level is one factor related to bacterial regrowth, BOM removal should be emphasized during water treatment to improve water quality. There is a weak correlation between organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC) concentrations. The BDOC test attempts to identify the entire pool of BOM, including very labile constituents to slowly biodegradable molecules (requiring the successive steps of cell adsorption, exoenzymatic hydrolysis, and cell consumption), whereas the AOC test detects easily assimilable organic compounds. Because both tests emphasize different fractions of biodegradable organic matter, both parameters should be monitored when studying nutrient changes during water treatment and distribution. Because of a long incubation period, using the BDOC suspended bacteria method is not practical at a water utility. A water utility can use either the sand or bioreactor methodology, depending on its testing objectives. Both methods yield to a similar BDOC result. The BDOC sand measurement is recommended for a short study or a limited number of samples.

Effect of easily biodegradable organic compounds on bacterial growth in a bench-scale drinking water distribution system

Many engineered (e.g., disinfectant residual concentration) and environmental (e.g., temperature) factors influence bacterial regrowth in drinking water distribution systems. This paper examines the effect of nutrients, specifically biodegradable organic matter (BOM) composition, BOM concentration, and hydraulic retention time on bacterial growth in an annular reactor (AR). Drinking water that had an alkalinity of 300 mg/L as CaCO3and a free chlorine residual of approximately 0.2 mg/L was used as process water in the ARs. Prior to entering the ARs, the water was filtered through granular activated carbon (GAC) to remove background chlorine and background organic matter. A cocktail of easily biodegradable organic compounds consisting of carboxylic acids, aldehydes, and free amino acids were spiked into the ARs as the primary carbon source. It was found that the influent BOM concentration (p value = 0.013) and the presence of free amino acids in the BOM cocktail (p value = 0.009) significantly increased the number of viable culturable cells in the biofilm, as measured by heterotrophic plate counts (HPCs). The interaction between the BOM concentration and the presence of amino acids also significantly increased the number of biofilm HPCs (p value = 0.021). Alternatively, the BOM concentration and the amino acid fraction did not affect the number of bulk (i.e., suspended) bacteria. The number of biofilm HPCs in the reactor was approximately 10 times greater than the number of bulk HPCs at high influent BOM concentrations and low retention times (i.e., high BOM loading rates). At low loading rates, the ratio of number of biofilm to bulk cells was less than 2. Consequently, it was deduced that the BOM was utilized predominately by the biofilm cells. This indicates that removal of easily biodegradable organic compounds is an important factor for controlling biofilm growth in distribution systems.Key words: drinking water, distribution systems, biofilm, annular reactor, regrowth.

Assessing biodegradable organic matter

High temperature, high BOM concentration, and low disinfectant residual promote regrowth of coliforms in distribution systems.This article summarizes data collected during various surveys that assessed four aspects of biodegradable organic matter (BOM) in drinking water: (1) BOM concentrations entering distribution systems, (2) the relationship between concentrations of assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC), (3) field tests of a simple method of measuring BDOC using bioreactors, and (4) the effect of BOM on coliform occurrences in distribution networks. Overall, average concentrations of AOC and BDOC in plant effluent were 100 μg/L and 0.32 mg/L, respectively. A statistically significant but weak relationship between AOC and BDOC concentrations suggests that both parameters need to be monitored during biostability studies because they provide different pieces of information. BDOC bioreactors are useful for measuring BDOC concentrations at water utilities. However, they require a long time to colonize and must adapt to water at the site where they are used. Coliform occurrences were associated with three factors: temperature, disinfectant type and concentration, and AOC concentration. When threshold values for these factors were exceeded (15oC, AOC &gt; 100 μg/L, and dead‐end disinfectant residuals &lt; 0.5 mg/L for free chlorine or 1.0 mg/L for chloramines), the probability of coliform occurrences greatly increased.

A NEW RAPID METHOD TO ASSESS OXYGEN DEMAND BASED ON THE HBOD PROBE

The 5-day biochemical oxygen demand (BOD 5 ) test has been used for over a century to evaluate the concentration of biodegradable organic matter in wastewater effluents. The BOD test is a simple batch test, but it is also time consuming, labor intensive, imprecise, and, due to the dilution of the wastewater, takes a relatively long time to complete. Advances in laboratory instruments and lab ware have made it possible to improve tests to measure oxygen demands of samples. Respirometric techniques are now widely used in Europe and are proposed for inclusion in Standard Methods. The headspace BOD (HBOD) test is a batch respirometric method that was developed only seven years ago. The test overcame many limitations of the BOD test, but its main shortcoming was that it was difficult to rapidly measure oxygen in the headspace of samples. We report here a new method to directly measure oxygen in the headspace of HBOD tubes using a fiber optic probe we refer to as an HBOD probe. We demonstrate that the HBOD probe provides data identical to that obtained with a gas chromatograph, but that sample analysis takes only minutes. Field tests conducted at two local wastewater treatment plants show that HBOD values are obtained in only 2 to 3 days that are similar to the BOD 5 values. We also demonstrate that HBOD values are more precise than those obtained in the BOD test.

Dissolved Organic Carbon Fractions Formed during Composting of Municipal Solid Waste: Properties and Significance

The properties and transformation of dissolved organic matter (DOM) extracted (10 L water per kilogram compost) from municipal solid waste (MSW) compost at five stages (days 47, 77, 105, 126, and 187) of composting were investigated. The DOM was fractionated into hydrophobic or hydrophilic neutrals, acids, and bases. The unfractionated DOM, the hydrophobic acids and neutrals (HoA and HoN, respectively), and the hydrophilic neutrals (HiN) fractions were studied using solid-state 13C-NMR, FTIR, and DRIFT spectroscopy. The HoA fraction was found to be the dominant (percentage of total DOM) hydrophobic fraction, exhibiting a moderate increase during composting. The HoN fraction increased sharply from less than 1% to 18% of the total DOM during 187 days of composting, while the hydrophobic bases (HoB) exhibited the opposite trend. The HiN represented the major fraction of the hydrophiles up to 120 days of composting, decreasing thereafter by 38%. The relative concentration of the hydrophilic acids and bases (HiA and HiB, respectively) exhibited no consistent trend during composting. DRIFT spectra of the unfractionated DOM taken from the composting MSW revealed a decreasing level of polysaccharide structures with time. The 13C-NMR and FTIR spectra of the HoA fraction exhibited a polyphenol-humic structure, whereas the HoN spectra exhibited strong aliphatic features. The spectra of the HiN fraction confirmed its polysaccharide nature. During the final stage of composting, the DOM concentration was steady, while a relative decrease of HiN concomitant with an increase of HoA and HoN fractions was observed. These indicate that the DOM contained a low concentration of biodegradable organic matter and a higher content of macromolecules related to humic substances. The biological significance and heavy metal binding of these fractions are being studied based on earlier observations showing enhanced plant growth in the presence of DOM extracted from mature as opposed to immature compost. Gelöster organisch gebundener Kohlenstoff bei der Kompostierung von Hausmüll: Eigenschaften und Anteil einzelner Fraktionen Untersucht wurden Eigenschaften und Umsetzung der gelösten organischen Substanz (dissolved organic matter – DOM) in Komposteluaten. Zur Gewinnung der DOM wurde kompostierter Hausmüll in verschiedenen Stadien der Kompostierung (47., 77., 105., 126. und 187. Tag) mit Wasser extrahiert (10 L Wasser auf 1 kg Kompost). Nach einem operationellen Fraktionierungsschema wurde die DOM aufgeteilt in hydrophobe und hydrophile Komponenten, innerhalb dieser beiden Kategorien noch einmal nach sauer, neutral und basisch. Die unfraktionierte DOM, die Fraktion hydrophob/sauer (HoA), die Fraktion hydrophob/neutral (HoN) und die Fraktion hydrophil/neutral (HiN) wurden mittels Festkörper-13C-NMR-, FTIR- und DRIFT-Spektroskopie untersucht. Innerhalb der hydrophoben Fraktionen dominierte die saure Fraktion, HoA, ihr Anteil an der Gesamt-DOM nahm im Laufe des Kompostierungsprozesses noch zu. Der Anteil der HoN-Fraktion stieg im Laufe der 187 Tage währenden Kompostierung stark an – von weniger als 1% auf 18% der gesamten DOM –, während die Fraktion hydrophob/basisch (HoB) die gegenläufige Tendenz entwickelte. Bei den hydrophilen Fraktionen stellte die neutrale Fraktion, HiN, bis zum 120. Tag der Kompostierung die Hauptfraktion dar; dann verringerte sich ihr Anteil um 38%. Für die Fraktionen hydrophil/sauer und hydrophil/basisch war keine eindeutige Tendenz im Verlauf der Kompostierung zu beobachten. Den DRIFT-Spektren der unfraktionierten DOM des Komposteluats ist zu entnehmen, daß im Verlauf der Kompostierung der Anteil an Polysaccharidstrukturen in der DOM zurückgeht. 13C-NMR- und FTIR-Spektren der HoA-Fraktion deuten auf Polyphenole und huminstoffähnliche Strukturen hin, während die Spektren der HoN-Fraktion von den charakteristischen Merkmalen aliphatischer Strukturen geprägt sind. Die Spektren der HiN-Fraktion bestätigen den Polysaccharidcharakter dieser Fraktion. In der letzten Phase der Kompostierung – nach etwa 100 Tagen –stellte sich eine stationäre DOM-Konzentration ein, dabei wird die relative Abnahme des Anteils der HiN-Fraktion an der DOM durch die gleichzeitige Zunahme des Anteils der Summe aus HoA- und HoN-Fraktion kompensiert. Das deutet darauf hin, daß in der DOM wenig bioabbaubare organische Stoffe und ein größerer Anteil an huminstoffartigen Makromolekülen enthalten waren. Auf dem Hintergrund einer früheren Beobachtung – verstärktes Pflanzenwachstum in Gegenwart von DOM aus Komposteluaten von gereiftem Kompost, der gegenteilige Effekt durch DOM aus Komposteluaten von jungem Kompost – sollen die biologische Bedeutung dieser Fraktionen und ihr Bindungsvermögen für Schwermetalle Gegenstand weiterer Forschung sein.

A gas chromatographic‐based headspace biochemical oxygen demand test

The 5‐day biochemical oxygen demand (BOD5) test is an established tool for measuring the concentration of biodegradable organic matter in wastewater effluents. Unfortunately, the BOD test is time consuming, labor intensive, and, due to the dilution of the wastewater, takes a relatively long time to complete. A few years ago a headspace BOD (HBOD) test was developed that avoided the need to dilute wastewater samples. A disadvantage of the original HBOD test was that the sample had to be transferred from the HBOD tube to another vessel for a dissolved oxygen measurement. This study demonstrates that it is possible to conduct HBOD tests using a gas chromatograph to measure oxygen utilization in the sealed tube and that a 3‐day HBOD provides a reliable estimate of the BOD5. The HBOD3 values measured for primary and secondary clarifier effluents from an activated sludge plant were 114 and 23 mg/L; BOD5 measurements were 116 and 24 mg/L. Changes in headspace volumes did not significantly change the HBODs. Secondary settled wastewater had a HBOD5 of 83 ± 3 mg/L (mean ± SD) for headspace volumes of 10–20 mL (36–71%) in a 28‐mL tube. The HBOD5 was also constant (84 ± 6 mg/L) when samples were diluted 20–60% using BOD dilution water at a fixed headspace volume of 8 mL in HBOD tubes. Nitrification increased the HBOD of nondiluted wastewaters after 4 days, although nitrification appeared to be sufficiently inhibited using a standard nitrification inhibitor. A calibration test for the HBOD was developed using a 300‐mg/L glucose and glutamic acid (GGA, 50% each) solution and secondary clarifier wastewater that provided HBOD3 values similar to those obtained in the analogous BOD5 test. It is argued that the simpler procedures, added precision of GC‐based protocols, and more rapid exertion of oxygen demand make the HBOD test superior to the conventional BOD test.