Organisms In Sludge Research Articles

Elimination of Cu(II) toxicity by powdered waste sludge (PWS) addition to an activated sludge unit treating Cu(II) containing synthetic wastewater

Copper(II) ion toxicity onto activated sludge organisms was eliminated by addition of powdered waste sludge (PWS) to the feed wastewater for removal of Cu(II) ions by biosorption before biological treatment. The synthetic feed wastewater containing 14 or 22 mg l −1 Cu(II) was mixed with PWS in a mixing tank where Cu(II) ions were adsorbed onto PWS and the mixture was fed to a sedimentation tank to separate Cu(II) containing PWS from the feed wastewater. The activated sludge unit fed with the effluent of the sedimentation tank was operated at a hydraulic residence time (HRT) of 10 h and sludge age (SRT) of 10 days. To investigate Cu(II), COD and toxicity removal performance of the activated sludge unit at different PWS loadings, the system was operated at different PWS loading rates (0.1–1 g PWS h −1) while the Cu(II) loading rate was constant throughout the operation. Percent copper, COD and toxicity removals increased with increasing PWS loading rate due to increased adsorption of Cu(II) onto PWS yielding low Cu(II) contents in the feed. Biomass concentration in the aeration tank increased and the sludge volume index (SVI) decreased with increasing PWS loading rate due to elimination of Cu(II) from the feed wastewater by PWS addition. PWS addition to the Cu(II) containing wastewater was proven to be effective for removal of Cu(II) by biosorption before biological treatment. Approximately, 1 g PWS h −1 should be added for 28 mg Cu h −1 loading rate for complete removal of Cu(II) from the feed wastewater to obtain high COD removals in the activated sludge unit.

Commissioning and operational experiences for the 160ML/d Woodman Point Sequencing Batch Reactor - control of settleability and denitrification using bioselectors

Achieving and maintaining good biomass settling characteristics is a critical process design objective for any activated sludge wastewater treatment plant (WWTP), whether intermittent or continuous technology. One way of ensuring good sludge settleability in intermittent WWTPs is the incorporation of bioselectors in the process. A bioselector is essentially a small discrete reactor volume designed primarily for carbon absorption, in which activated sludge organisms are exposed to a high substrate concentration for a relatively short time. It is normally very much smaller than an anoxic zone and the activated sludge recycle is only a fraction of that typically adopted in continuous plants. With proper conditioning, recycled biomass rapidly absorbs and stores soluble organic wastewater components before transfer to the main treatment basin. This absorption and storage mechanism, and careful management of aeration throughout the intermittent treatment cycle, plays a crucial role in many subsequent growth and treatment processes, including sludge floc formation, denitrification and biological phosphorus removal. This paper examines some design considerations, and reviews the benefits of bioselectors by reference to the commissioning and initial operation of the new 160ML/d Woodman Point Sequencing Batch Reactor in Perth, Western Australia. The applicability of bioselectors in continuous plants is discussed.

Toxicity of metals and organic chemicals evaluated with bioluminescence assays

The development of a bioluminescent sensor organism (Shk1) that was created for assessing wastewater toxicity was reported several years ago. In order to establish a test battery to better characterize wastewater toxicity, additional luminescent sensor organisms were later created. The present study focused on one promising candidate (PM6), a Pseudomonas spp. strain, because of its high level of luminescence compared to that of other newly created organisms. Using a batch toxicity testing protocol, the toxicity of 7 metals and 25 organic compounds was evaluated with the PM6 and Shk1 assays. Results indicated that the toxicity data of the PM6 and the Shk1 assays were correlated, and no assay appeared to be particularly more sensitive to a group of toxicants than the other assay. The results of the PM6 and Shk1 assays were further evaluated by comparing with the results of the Vibrio fischeri luminescence inhibition assay and activated sludge inhibition assays. Data suggested that PM6 and Shk1 more closely represented activated sludge organisms than V. fischeri. The suitability of using PM6 and Shk1 for assessing wastewater toxicity on activated sludge, both individually and in a test battery, was discussed.

Concentrations and inactivation of Ascaris eggs and pathogen indicator organisms in wastewater stabilization pond sludge

During treatment in wastewater stabilization ponds (WSPs) many pathogens, in particular helminth eggs, are concentrated in the sludge layer. Because periodic removal of the sludge is often required, information is needed on the concentrations and inactivation of pathogens in the sludge layer to evaluate the public health risk they pose upon removal of the sludge. In this paper, previous reports on the sludge concentrations of various pathogen indicator organisms and helminth eggs are reviewed and results from our own recent experiments are reported. The advantages and disadvantages of several methods for studying inactivation in the sludge layer are discussed, as well as implications for the management of WSP sludge. In our recent experiments, which were conducted at three WSPs in central Mexico, sludge cores, dialysis chambers, and batch experiments were used to measure the inactivation rates of fecal coliform bacteria, fecal enterococci, F+ coliphage, somatic coliphage, and Ascaris eggs. The first-order inactivation rate constants were found to be approximately 0.1, 0.1, 0.01, 0.001, and 0.001 d(-1), respectively. The concentrations of all the organisms were found to vary both vertically and horizontally in the sludge layer; therefore, to determine the maximum and average concentration of organisms in the sludge layer of a WSP, complete sludge cores must be collected from representative locations throughout the pond.

Detection of the microbial activity of aerobic heterotrophic, anoxic heterotrophic and aerobic autotrophic activated sludge organisms with an electrochemical sensor

The microbial activity of aerobic heterotrophic, anoxic heterotrophic and aerobic autotrophic microorganisms in biological wastewater treatment was determined by means of an electrochemical bioactivity sensor. The development of the sensor resulted in a system which can determine the microbial activities that are relevant for effective wastewater treatment. The signals of the sensor system are proportional to the substrate degradation and it can show inhibiting effects on the biomass. The most important advantages of the system are: it is independent of O2 consumption, the three most important types of metabolic activities in wastewater technology can be measured with one sensor, furthermore the measurement is suitable for automation and it is on-line. The result is a potential for the optimization of processes based on microbial activity.

The Importance of Pathogenic Organisms in Sewage and Sewage Sludge

ABSTRACT Deficient sanitation poses a serious threat to human and animal health, involving complex relationships between environments, animals, refuse, food, pathogens, parasites, and man. However, by sanitizing and stabilizing the organic matter of sewage sludge, agriculture can utilize it to maintain soil, water, and air quality. As ingredients in soil amendments, such bioresidues are a source of nutrients for plants. Stabilization and sanitation of sewage sludge safely couple its recycling and disposal. This coupling becomes increasingly important as economic and environmental constraints make strategies for waste disposal more difficult to apply. The occurrence of viruses, bacteria, yeasts, fungi, and zooparasites in sewage sludge is reviewed in this article, and consequential epidemiologic concerns that arise from sewage sludge recycling is also addressed.

Enhanced biological phosphorus removal in an anaerobic-aerobic sequencing batch reactor: effect of pH.

Enhanced biological phosphorus removal (EBPR) is not always successfully achieved in activated-sludge processes by anaerobic-aerobic operation. It has been reported that the deterioration of EBPR has been caused by domination of glycogen-accumulating organisms (GAOs) in microbial sludge. After repeated operation of a sequencing batch reactor (SBR) supplied with acetate as a sole carbon source, it was found that an operational variable, pH, could be a tool to control the competition between GAOs and polyphosphate-accumulating organisms PAOs, which could mediate the success of EBPR. When anaerobic phase pH in the SBR was controlled at 7.0, GAOs dominated the culture, resulting in failure of EBPR. Without pH control, the pH during the anaerobic phase increased to 8.4 as a result of denitrification and acetate uptake. In this relatively high pH condition, almost complete EBPR was achieved. In this report, the mechanism of pH effect on the competition between GAOs and PAOs was elucidated through a characterization of activated sludge using previously proposed biochemical models.

Innovative methods for sludge characterization in biological phosphorus removal systems

This paper describes several techniques and methods for sludge characterization which are recently developed and used in our ongoing research on biological phosphorus removal (BPR): (i) chemical measurement of the poly-hydroxy-alkanoate (PHA) content of the biomass, (ii) bioassay for glycogen determination in BPR systems, (iii) determination of the fraction of denitrifying phosphorus accumulating organisms (DPAOs) in P-removing sludge, (iv) determination of the aerobic and anoxic ATP/NADH2 ratio (δ value) in BPR systems, and (v) determination of the glycogen accumulating organisms (GAOs) / phosphorus accumulating organisms (PAOs) ratio in activated sludge.

Innovative methods for sludge characterization in biological phosphorus removal systems

This paper describes several techniques and methods for sludge characterization which are recently developed and used in our ongoing research on biological phosphorus removal (BPR): (i) chemical measurement of the poly-hydroxy-alkanoate (PHA) content of the biomass, (ii) bioassay for glycogen determination in BPR systems, (iii) determination of the fraction of denitrifying phosphorus accumulating organisms (DPAOs) in P-removing sludge, (iv) determination of the aerobic and anoxic ATP/NADH2 ratio (δ value) in BPR systems, and (v) determination of the glycogen accumulating organisms (GAOs) / phosphorus accumulating organisms (PAOs) ratio in activated sludge.

Compliance outlook: meeting 40 CFR part 503, class B pathogen reduction criteria with anaerobic digestion

ABSTRACT: The current federal sludge regulations for the first time place limitations on the concentration of pathogens or indicator organisms in sludge and sludge products destined for distribution and marketing and land application. However, there is a general lack of data for assessing the impacts of these new limits on the wastewater industry. To understand better the extent of the compliance problem and the factors that may enable publicly owned treatment works (POTWs) using anaerobic digestion to comply with the new criteria, a survey of treatment plants around the U.S. was undertaken. In addition to data on fecal coliform densities in raw and digested sludge, information was collected on the design and operating characteristics of the 54 digestion facilities that participated in the survey. Based on the analysis of survey responses, it appears that the pathogen reduction criteria under the regulations are not unreasonable and should be achievable by most conventional anaerobic digestion facilities.

Effect of time, daylight, and settling pond microorganisms on the high molecular weight fraction of kraft bleachery effluents

Changes occurring in the pH-stable fraction of high molecular weight (HMW) (> 1 kD) fraction of combined C- and E-stage bleachery effluents from hardwood and softwood kraft mills were followed over 16 weeks. Incubated in water at 20–23°C and neutral pH, this HMW material, generally considered to be the most refractory part of kraft mill effluent, showed substantial and continuing mineralization of its HMW adsorbable organic halogen (AOX) to chloride ions, via both daylight-dependent and daylight-independent mechanisms. Significant decreases were also seen in HMW color and apparent molecular size. Comparison of filter-sterile HMW material and the same material inoculated with settling pond sludge organisms indicated that, over 16 weeks, microbial processes were not important in the observed HMW AOX mineralization or chromophore bleaching, and that the HMW carbon was largely unavailable, at least to the microbial consortium employed. The microflora did, however, reduce toxicity, as measured with the Microtox assay. Thus the results suggest that HMW kraft bleachery AOX degrades abiotically to release chloride over a relatively short time span (in ecosystem terms) under conditions similar to those typical of many receiving waters.

Fate of indicator organisms in sludge during bacterial leaching of metals

Biological extraction (bacterial leaching) of heavy metals from digested sewage sludge has been shown to be a practical means for decontaminating sludge for use on agricultural land. However, it was not known whether pathogenic organisms would survive or be destroyed in the acidic environment necessary for the bacterial leaching process. The purpose of the research reported herein was to assess the effect of bacterial leaching on various bacteria commonly used to indicate the possible presence of pathogenic organisms. Although pathogenic viruses, bacteria, protozoa, and helminths may be present in sludge, this study is concerned only with bacterial pathogens. The concentrations of the four indicator bacteria selected to represent the bacterial pathogens were determined in a series of laboratory bacterial leaching units. Results showed that, although about 80–90% metal removal efficiencies were achieved (at a pH of 4.0, an aeration rate of 100 mL of air per minute per litre of sludge) at a temperature of 20–25 °C, the indicator bacteria were not reduced during bacterial leaching at high suspended solids concentrations. The survival of indicator bacteria was found to be a function of the suspended solids concentration in the leaching units, regardless of the source or type of indicator bacteria. At suspended solids concentrations greater than 10 g/L, the indicator bacteria were able to survive, apparently unaffected by the unfavourable environmental conditions (10 days retention at pH 4.0). Below this suspended solids concentration of 10 g/L, significant reductions of total coliforms, faecal coliforms, and faecal streptococci were achieved. Total heterotrophs did not follow the same trends as the other indicator bacteria. Key words: bacterial leaching, Thiobacillus ferrooxidans, indicator bacteria, enteric pathogens removal, sewage sludge, sludge disposal.

Thermophilic anaerobic degradation of carbohydrates - metabolic properties of microorganisms from the different phases

Organisms that might participate in anaerobic, thermophilic degradation of carbohydrates to methane and CO2 and their metabolic properties are shortly reviewed in this paper. More than 20 thermophilic species of classical, fermentative bacteria and of archaebacterial methane bacteria from thermophilic ecosystems have been described and thermophilic acetogenic butyrate- and acetate-degrading consortia have been enriched. As shown for mesophilic degradation thermophilic sulfate reducers might also serve as potential acetogens for the degradation of organic acids and of ethanol in syntrophy with thermophilic methanogens. However, no experimental data are yet available. Pure cultures of thermophilic ‘fermentative’ bacteria can degrade a variety of different sugars and polysaccharides, irrespective of their origin, which was either sewage sludge, soil or a solfataric environment. The sewage sludge organisms Acetomicrobium flavidum and Acetothermus paucivorans fermented glucose via the EMP-pathway to 2 acetate, 2 CO2 and 4 H2. This fermentation stoichiometry is unique for pure cultures and was previously observed only in syntrophic associations of mesophiles with methanogens or sulfate reducers. Generally, the spectrum of metabolites of thermophilic fermentative isolates seems to be more restricted than that of mesophiles. All methanogenic strains were isolated from sludge or wastewater digesters except for the two Methanothermus species and the thermophilic Methanococcus species, which were from volcanic ecosystems. The substrate spectrum and the metabolism of the thermophilic methanogens did not differ from that of mesophilic representatives. In summary the scheme of Bryant [1] is also suitable for the description of the carbon flow during anaerobic carbohydrate degradation by thermophiles. The complexity of intermediates was dependent on the efficiency of interspecies H2-transfer.

Thermophilic anaerobic degradation of carbohydrates - metabolic properties of microorganisms from the different phases

Organisms that might participate in anaerobic, thermophilic degradation of carbohydrates to methane and CO 2 and their metabolic properties are shortly reviewed in this paper. More than 20 thermophilic species of classical, fermentative bacteria and of archaebacterial methane bacteria from thermophilic ecosystems have been described and thermophilic acetogenic butyrate- and acetate-degrading consortia have been enriched. As shown for mesophilic degradation thermophilic sulfate reducers might also serve as potential acetogens for the degradation of organic acids and of ethanol in syntrophy with thermophilic methanogens. However, no experimental data are yet available. Pure cultures of thermophilic ‘fermentative’ bacteria can degrade a variety of different sugars and polysaccharides, irrespective of their origin, which was either sewage sludge, soil or a solfataric environment. The sewage sludge organisms Acetomicrobium flavidum and Acetothermus paucivorans fermented glucose via the EMP-pathway to 2 acetate, 2 CO 2 and 4 H 2. This fermentation stoichiometry is unique for pure cultures and was previously observed only in syntrophic associations of mesophiles with methanogens or sulfate reducers. Generally, the spectrum of metabolites of thermophilic fermentative isolates seems to be more restricted than that of mesophiles. All methanogenic strains were isolated from sludge or wastewater digesters except for the two Methanothermus species and the thermophilic Methanococcus species, which were from volcanic ecosystems. The substrate spectrum and the metabolism of the thermophilic methanogens did not differ from that of mesophilic representatives. In summary the scheme of Bryant [1] is also suitable for the description of the carbon flow during anaerobic carbohydrate degradation by thermophiles. The complexity of intermediates was dependent on the efficiency of interspecies H 2-transfer.

Assessing detoxification of a complex hazardous waste, using the Microtox bioassay.

Research has demonstrated the usefulness of the Microtox™bioassay in assessing the acute toxicity of organic compounds. Recently, the use of the Microtox™bioassay has been extended to applications in hazardous waste management. The rapidity of the test, low sample requirements, and low cost provide several advantages over chemical analysis, especially for complex waste mixtures. Microtox™bioassay results correlate closely with results from rainbow trout bioassays, and are more sensitive to inhibitory chemicals than activated sludge organisms. An experimental approach using batch reactors and soil columns was implemented in the laboratory to evaluate the detoxification and mobility of a toxic complex hazardous waste in soil. The objective of the study reported here was to quantify the extent and rate of detoxification of a complex hazardous waste as affected by soil type and waste application rate. The extent and rate of detoxification was directly related to waste loading rate for both soil types investigated, in both batch reactors and soil column reactors. Analysis of the toxicity of aqueous soil extracts at incremental depths through soil columns and of soil columnn leachate indicated a low leaching potential for the complex petroleum refinery waste.

Biochemical oxidation of dissolved organic matter by sludge organisms.

This paper presents an experimentally verified theory for the mathematical and biochemical progression of aerobic degradation of dissolved organic matter. The stoichiometric model of biochemical oxidation of organic matter is proved by three reactions: 1) the combination of the synthesis of microbial cells directly and oxidative conversion into another carbohydrate, 2) the synthesis of microbial cells from the carbohydrate, and 3) the oxidation of microbial cells through endogenous respiration. On the basis of the three chemical reactions, the progress of BOD is mathematically represented as the sum of three first order kinetics. Kinetics parameter is deter-mined by the modification of Lee's graphical method. Excluding the affects of nitrification, the curve obtained from the sum of three first order kinetics agrees well with the observed data. The agreement between the theoretical oxygen demand calculated from chemical equation and experimental ultimate oxygen demand obtained from kinetic analysis of data is excellent for reactions in the microbial growth phase (the reaction of 1 and 2 noted above). And the experimental data on bio-oxidation solids production corresponds very nearly to the theoretical value obtained from chemical equation.

Evaluation of the toxicity of substances to be assessed for biodegradability

The ability to distinguish between true non-biodegradability, and inhibition of biodegradability due to the toxic effects of the compound tested present problems. It results in possible false identification of substances as non-biodegradable. Six chemicals were evaluated in a variety of tests to assess their toxicity to aerobic sludge organisms. The tests employed were: BOD 5 and Closed Bottle inhibition tests, inhibition of respiration of activated sludge, growth inhibition of activated sludge, light emission from Photobacterium phosphoreum (MICROTOX test) and the repetitive die-away test (RDA). Results from these tests were compared with results obtained from a number of ready biodegradability tests using the compounds listed above at anticipated non-toxic and toxic concentrations. No test method evaluated consistently forecast toxicity due to the chemicals tested. The MICROTOX and nitrification inhibition tests were too sensitive. A combination of sludge respiration rate and/or growth tests seem most appropriate. To avoid toxicity to the sludge, biodegradability testing should be made at 10% of the EC 50 value. Compounds with an EC 50 value greater than 300 mg/l are unlikely to be toxic in ready biodegradability tests. Compounds with an EC 50 value of less than 20 mg/l may pose problems necessitating the use of the stringent closed bottle test, or the use of C 14 labelled test materials. Compounds with an intermediate EC 50 that is between 20–300 mg/l, need to be evaluated at a range of concentrations in biodegradability tests, or may need to be evaluated carefully to define the precise no-effect level. Procedure recommendations to distinguish between the inhibition of biodegradability and inertness of the test substance are made.

A kinetic model for anaerobic digestion of biological sludge

The principal objective of this study was the development and evaluation of a comprehensive kinetic model capable of predicting digester performance when fed biological sludge, preliminary conversion mechanisms such as cell death, lysis, and hydrolysis responsible for rendering viable biological sludge organisms to available substrate were studied in depth. The results of this study indicate that hydrolysis of the dead, particulate biomass-primarily consisting of protein-is the slowest step, and therefore kinetically controls the overall process of anaerobic digestion of biological sludge. A kinetic model was developed which could accurately describe digester performance and predict effluent quality.

Hydrogen-using bacteria in a methanogenic acetate enrichment culture.

In a study of the anaerobic utilization of acetate, an enrichment culture of sewage sludge organisms was initiated with calcium acetate as the sole carbon and energy source. A mixed bacterial population became established from which 14 anaerobic species were isolated. Two of the isolates were methanogenic bacteria but only one of these, Methanosarcina barkeri, utilised acetate as an energy source in axenic culture. The other methanogenic isolate, a Methanobacterium sp., utilised H2/CO2 but not acetate. A third methanogen, which was morphologically identical to Methanothrix soehngenii, was detected in the enrichment but was not obtained in monoculture. 2-Bromoethanesulphonate, a specific inhibitor of methanogenesis, completely inhibited the enrichment at a concentration of 10 mumol/l. Addition of H2 formate or methanol to the enrichment did not affect the rate of methanogenesis. An H2-utilizing Desulfovibrio sp. was also isolated from the enrichment.

活性汚泥中の糸状微生物量と汚泥の膨化との関連性

In the previous paper, one of the authors showed a method to determine the quantity of all filamentous organisms in activated sludge by both filament length and filament volume per unit weight of dried sludge. The former was defined as specific length of total filaments and the latter specific volume of total filaments, respectively. In this paper, relationship between these quantitative estimates and bulkiness of activated sludge was examined using activated sledges obtained from various treatment plants. The bulkiness of activated sludge was determined using Standard SVI at 20 C. Following aspects were indicated.1) Increase of filamentous organisms in activated sludge made the sludge more and more bulky.2) Specific volume of total filaments showed higher correlation to Standard SVI than specific length of total filaments did. 3) Bulking of activated sludge may occur at about 2 per cent of filament content in activated sludge organisms.