Transformation and characterisation of dissolved organic matter during the thermophilic aerobic biodegradation of faeces

We conducted a comparison of the characteristics of dissolved organic matter (DOM) taken from the bio-toilet and other sources. A characterisation of DOM was carried out to assess the stability of the compost generated during the thermophilic and aerobic biodegradation of faeces. In addition, levels of soluble microbial products generated in the bio-toilet composting reactor were compared with those taken from other sources. The results showed that (i) the main component of DOM from the bio-toilet are solutes with molecular weight (MW)>30,000 Da (40%), whereas micromolecules (MW< 1000 Da) constituted more than 60% of the DOM from other solid samples, while liquid samples reached even more than 90%; (ii) the DOM stabilisation level in the composting reactor of the bio-toilet system was greater than that shown by DOM from other sources; (iii) stabilisation of DOM in the bio-toilet system was characterised by an increasing amount of macromolecules (MW>30,000 Da) after a decreasing trend was observed in the early stages of the biodegradation process; and (iv) net production of lipopolysaccharide (LPS) in wastewater treatment plants is greater than in the bio-toilet.     

Effect of anionic and nonionic surfactants on the kinetics of the aerobic heterotrophic biodegradation of organic matter in industrial wastewater

While using the contemporary mathematical models for activated sludge systems, it is necessary to describe quantitatively the kinetics of microbiological processes and to characterise substrate (wastewater components in the influent) as well as biomass (activated sludge). In this paper, the kinetic parameters of the aerobic biodegradation of organic matter in wastewater containing synthetic surfactants in an activated sludge system were determined and discussed. Also, the composition of the tested wastewater was estimated and expressed as COD fractions. Five synthetic surfactants, three anionic and two nonionic, of different chemical structure were investigated. Each of them was tested separately and dissolved in wastewater to obtain a concentration of 50 mgl(-1), which can be found in some industrial wastewater. The presence of the elevated amount of synthetic surfactants in wastewater decreased the affinity of biomass to substrate. Nevertheless, maximum specific growth rates (micromax) of heterotrophic biomass exposed to wastewater containing surfactants were high but usually lower than micromax estimated for wastewater without surfactant. Surfactants, which contain a benzene ring, were the most likely to deteriorate wastewater treatment processes in the activated sludge systems.     

污泥堆肥温度对微生物降解有机质的影响

污泥自然通风静态堆肥试验研究表明,堆肥过程中温度的变化引起微生物数量和种群的交替变化,从而影响对有机质的分解。而污泥堆肥过程有机质的降解主要是在中温阶段完成的,其中中,高温菌群起重要的作用。     

Genotoxic activity of nitroarene-contaminated industrial sludge following large-scale treatment in aerated and non-aerated sacs

An industrial sludge containing a complex mixture of nitroaromatic compounds was treated in industrial large-scale aerobic and anaerobic biodegradation processes, performed in compost sacs. The goal was to study changes in genotoxicity during the two different oxygen regimes using the umuC genotoxicity assay. The composting sac was actively aerated during 3 months and allowed to mature for another 3 months. The anaerobic sac was not aerated for 5 months and aerated during the last month in order to enhance degradation of remaining organic carbon. The sludge was obtained from the wastewater treatment plant at an industrial area in Karlskoga, Sweden. The biodegradation study was performed at a commercial waste treatment plant in Stockholm, according to the company routine procedure when treating household waste in sealed sacs. The material from the non-aerated system showed increased genotoxicity in the acetone-soluble fraction after treatment, as did the water-soluble fraction. The subsequent aeration period did not decrease the toxicity below the genotoxicity limit. The increase in the water-soluble genotoxic compounds may pose an environmental problem during secondary storage or use of sludge treated this way, since leakage of water-dissolved genotoxic compounds may occur. The composting process also generated genotoxicity, but this was restricted to acetone-soluble compounds, while the water-soluble compounds remained low in genotoxicity. The aerated process therefore seems more favorable in term of risk reduction of this industrial sludge, although it is necessary to optimize the aerated process in order to achieve non-toxic levels of potential genotoxic compounds extractable by organic solvents.     

Microbial degradation of a new detergent builder, carboxymethyltartronate (CMT), in laboratory activated sludge systems

An approach for determining the biodegradability of new detergent builders under activated sludge conditions was investigated using carboxymethyltartronate (CMT) as a representative material. Preliminary biodegradation studies in river water and activated sludge indicated a 4–8 week period before acclimation to and biodegradation of CMT. More detailed studies in continuous flow activated sludge units established that acclimation to CMT degradation was not readily lost upon CMT starvation, could be maintained at low temperatures and under conditions of variable organic loading, and was unaffected by the presence of a variety of metal ions. The laboratory evaluation of CMT, which stressed the use of natural sewage/activated sludge systems in place of tests employing commercially available laboratory media, would predict CMT to be satisfactorily removed in full-scale activated sludge waste treatment plants.     

Biodegradation of nonylphenol polyethoxylates by denitrifying activated sludge

Biodegradation of nonylphenol polyethoxylates (NPEOs) by denitrifying activated sludge was investigated. The results showed that NPEOs were readily degraded in the denitrifying activated sludge process. Organic substance, initial concentration, and temperature had great influence on biodegradation of NPEOs in the denitrifying activated sludge process while the influence of biodegradation intermediates such as nonylphenol (NP) could be neglected. Biodegradation of NPEOs was severely inhibited in the presence of organic substances. Different organic substances had different inhibition ability on the biodegradation of NPEOs. The maximum biodegradation rate increased 2.51 microM d(-1) for each 10 microM increase in initial concentration of NPEOs. This linear relationship was maintained even at relatively high initial concentration. The decrease in temperature caused a sharp decrease in the removal efficiency of NPEOs. The temperature coefficient (Phi) for the biodegradation of NPEOs in the denitrifying activated sludge process was 0.011 degrees C(-1). NPEOs were biodegraded through a nonoxidative pathway, through which NPEOs were degraded via sequential removal of ethoxyl units (as acetaldehyde) to NP. Compared to anaerobic activated sludge treatment, denitrifying activated sludge treatment had much higher removal efficiency of NPEO contaminants. To our knowledge, it is the first report on the biodegradation of NPEOs in denitrifying activated sludge process.     

Biodegradation of a cationic surfactant in activated sludge

The biodegradation of DTDMAC (ditallowdimethylammonium chloride, a fabric softening agent) was established in semi-batch activated sludge reactors. Three ¹⁴C-forms of DTDMAC were studied separately under the simulated organic loading rates of conventional and extended aeration activated sludge treatment. Primary biodegradation was shown by means of a specific analytical technique in combination with radiochemical procedures. Ultimate biodegradation for each carbon position in the DTDMAC molecule was established by the detection of ¹⁴CO₂. Intermediate metabolites were followed throughout the study by both radio thin-layer chromatography and radiochemical procedures. Each carbon position of the DTDMAC molecule was equally accessible to metabolism and ultimate degradation by acclimated microorganisms. Degradation occurred more rapidly under extended aeration conditions and was influenced by the strong tendency of DTDMAC to associate with the microbial population. The low levels of metabolites observed were not of a single classification or characteristic and they did not persist in the activated sludge. This study suggests that DTDMAC removal in an activated sludge plant is a result of both sorption/precipitation and biodegradation mechanisms.     

Fractionating soluble microbial products in the activated sludge process

Soluble microbial products (SMP) are the pool of organic compounds originating from microbial growth and decay, and are usually the major component of the soluble organic matters in effluents from biological treatment processes. In this work, SMP in activated sludge were characterized, fractionized, and quantified using integrated chemical analysis and mathematical approach. The utilization-associated products (UAP) in SMP, produced in the substrate-utilization process, were found to be carbonaceous compounds with a molecular weight (MW) lower than 290 kDa which were quantified separately from biomass-associated products (BAP). The BAP were mainly cellular macromolecules with an MW in a range of 290-5000 kDa, and for the first time were further classified into the growth-associated BAP (GBAP) with an MW of 1000 kDa, which were produced in the microbial growth phase, and the endogeny-associated BAP (EBAP) with an MW of 4500 kDa, which were generated in the endogenous phase. Experimental and modeling results reveal that the UAP could be utilized by the activated sludge and that the BAP would accumulate in the system. The GBAP and EBAP had different formation rates from the hydrolysis of extracellular polymeric substances and distinct biodegradation kinetics. This study provides better understanding of SMP formation mechanisms and becomes useful for subsequent effluent treatment.     

Molecularly imprinted polymer microspheres enhanced biodegradation of bisphenol A by acclimated activated sludge

The impacts of bisphenol A− imprinted polymeric microspheres (MIPMs) on the biodegradation of bisphenlol A by acclimated activated sludge were studied. Due to the selective adsorption of MIPMs to bisphenol A (BPA) and its analogues, addition of MIPMs to activated sludge increased levels of BPA and its metabolites, which were also the substrates of biodegradation. Higher substrates (BPA and its metabolites) level promoted biodegradation efficiencies of activated sludge via accelerating removal speed of BPA and its metabolites, increasing degradation rate and decreasing half-lives of biodegradation. The enhancement of MIPMs in degradation efficiencies was more significant in environmental water containing low-level of pollutants, and water containing interferences such as heavy metals and humic acid. Furthermore, MIPMs were more suitable than non-selective sorbents such as active carbon to be used as enhancer for BPA biodegradation. MIPMs combined with activated sludge are simple, effective, environmental-friendly processes to biodegrade low-level pollutants in environmental water.     

污水厂剩余污泥好氧堆肥工艺参数的控制

对银川市污水处理厂产生的剩余污泥进行了好氧堆肥中试研究,重点考察了对污泥含水率、通风方式等参数的控制.结果表明,在剩余污泥的含水率为80%左右的条件下,采用自然晾晒3～5 d的干燥方式即可基本达到进料污泥的最佳含水率范围(50%～60%),节省了掺混污泥调理剂的费用;最佳的堆肥通风方式为间断强制通风;污泥经初次、二次发酵后,对蛔虫卵的杀灭率达到100%,总大肠菌群数≤100 个/kg(降低了约5～7个数量级);堆肥成品呈疏松的团粒结构,无恶臭气味,无蚊蝇孳生.     

Micropollutant removal by attached and suspended growth in a hybrid biofilm-activated sludge process

Removal of organic micropollutants in a hybrid biofilm-activated sludge process was investigated through batch experiments, modeling, and full-scale measurements. Batch experiments with carriers and activated sludge from the same full-scale reactor were performed to assess the micropollutant removal rates of the carrier biofilm under oxic conditions and the sludge under oxic and anoxic conditions. Clear differences in the micropollutant removal kinetics of the attached and suspended growth were demonstrated, often with considerably higher removal rates for the biofilm compared to the sludge. For several micropollutants, the removal rates were also affected by the redox conditions, i.e. oxic and anoxic. Removal rates obtained from the batch experiments were used to model the micropollutant removal in the full-scale process. The results from the model and plant measurements showed that the removal efficiency of the process can be predicted with acceptable accuracy (±25%) for most of the modeled micropollutants. Furthermore, the model estimations indicate that the attached growth in hybrid biofilm-activated sludge processes can contribute significantly to the removal of individual compounds, such as diclofenac.     

污泥堆肥动力学分析及工程启示

主要分析了堆肥体中物料的固、液、气三相及其界面的反应和传质过程,从微观动力学角度进行模拟计算,并分析了堆体内的反应、传质和传热过程,由此揭示污泥堆肥过程的影响因素及相互关系。通过计算分析堆肥过程动力学的控制因素,提出污泥堆肥工程优化的原则。     

Effect of ZnO particles on activated sludge: role of particle dissolution

The release of nanoparticles (NPs) into the environment, including wastewater treatment plants, is expected to increase in the future. Therefore, it is important to understand the potential effects of these NPs on activated sludge treatment processes. A pulse-flow respirometer was used to study the toxicity of nano-ZnO on activated sludge endogenous respiration, BOD biodegradation, and nitrification. In addition, toxicities of bulk ZnO particles and Zn ion (e.g. soluble Zn) were also studied. All three Zn forms were found to adversely impact the activity of activated sludge, with soluble Zn exhibited the greatest toxicity. The effects of nano-ZnO and bulk ZnO on activated sludge were caused by soluble Zn resulting from ZnO particle dissolution. The IC₅₀ values of soluble Zn on activated sludge endogenous respiration, BOD biodegradation, ammonia oxidation, and nitrite oxidation were 2.2, 1.3, 0.8, and 7.3 mg-Zn/L, respectively. Therefore, the first step of nitrification was most sensitive to Zn.     

城市污泥堆肥过程自动测控系统及其应用

针对城市污泥堆肥过程控制存在的问题,设计开发了一套自动测控系统(CTB),并进行了应用研究。结果表明,与简单定时控制相比,CTB堆肥自动测控系统可缩短堆肥时间28%,使有机物降解更加充分,堆肥产品质量得以提高。     

A water-sediment screening tool for measuring biodegradation of organic chemicals

A water-sediment screening tool (WSST) was developed based on OECD guideline 301 C (MITI I; Ministry of International Trade and Industry, Japan) to generate biodegradation data. The WSST and experimental procedures were tested and validated using aniline (CAS No. 62-53-3) and benzoic acid (CAS No. 65-85-0) as reference substances. In the presence of sediment components a higher endogenous respiration rate in the control vessels without test substance was measured compared to the water-only MITI test system, particularly due to organic constituents. However, it could be demonstrated that a distinct biodegradation in the presence of sediment can be determined and that there is no influence of the sediment pre-treatment on the biological oxygen demand in the WSST. Experiments resulted in biodegradation rates > 60% after approximately six days for both compounds. However, degradation of benzoic acid resulted in a shorter lag-phase and a higher degree of degradation compared to aniline. Differences in results between the MITI test system and the WSST observed for aniline can be explained by adsorption to constituents of the sediment and assimilation by activated sludge. In comparison with literature data the results obtained for aniline in the MITI test system and the WSST showed reproducibility and were within the expected range. In conclusion, the WSST is a suitable screening tool to determine kinetic biodegradation data required to predict the biodegradation behaviour of organic chemicals in water-sediment systems and the data might be used to improve quantitative structure-property relationships (QSPRs).     

Monitoring of the evolution of an industrial compost and prediction of some compost properties by NIR spectroscopy

Sewage treatment plants produce wastes resulting from the organic matter concentration in the form of sludge. A way of jointly treating and exploiting these increasing wastes jointly is the composting. Composting makes it possible to reduce volumes and the masses of wastes all while developing them in a product usable like organic soil enrichment. In this work, the composting process of an industrial sewage sludge composting plant was monitored to study the evolution of different physico-chemical parameters (temperature, moisture, pH, organic carbon, organic and inorganic nitrogen, organic carbon/organic nitrogen ratio, humic substances) and biochemical parameters (soluble fraction, hemicellulose, cellulose, lignin). Because these analyses are expensive and time consuming, we wanted to develop an alternative method to determine the maturity of compost related to compost properties with raw samples. Acceptable predictions were found for moisture, temperature, pH, organic carbon, organic carbon/organic nitrogen ratio, total-, organic- and ammoniacal nitrogen, fulvic- and humic acids and fulvic acids/humic acids ratio, but the error values were too high for the compost age to consider a quantification model. With regard to the biochemical parameters, this study is rather a preliminary test which shows the interest of the approach, but requires to be continued. Finally, the age of compost can be evaluated with Principal Component Analysis applied to NIR spectra.     

Active biomass in activated sludge mixed liquor

The engineering and technology of the activated sludge system are reasonably well established, with systems implemented worldwide for the biological removal of C, N and/or P. Parallel to this development, significant advances have been made in the microbiological and biochemical areas of activated sludge. These advances have been driven by the development of new analytical techniques that allow microorganisms to be studied in situ in the activated sludge environment. However, there has been little cross-linking and overlap between the engineering and technology and microbiology and biochemistry paradigms. In particular, the information from the microbiology and biochemistry has not been integrated into the engineering and technology paradigm, to enable improved system design and optimization. One area that can form a starting point to build bridges between the two paradigm sets, is measurement of active biomass. The current design and simulation models invariably include active biomass for each organism group as fundamental parameters which define quantitatively the kinetic rates of the relevant biological processes. However, these parameters remain purely hypothetical because to date they have not been quantitatively measured; their acceptance is based on the consistency of model predicted results over a wide range of application. This paper describes developments in quantitative measurement of the heterotrophic and autotrophic active biomass concentrations within the engineering and technology paradigm, and the formulation of a multinational project which will attempt to link these measurements and the defined engineering environment to the new microbiological and biochemical analytical techniques. It is hoped that this project will facilitate integration of the two paradigms sets.     

Prediction of multicomponent adsorption equilibria in background mixtures of unknown composition

In the past, most predictive mathematical modeling work has focused on mixtures of known composition. Unfortunately, drinking water and wastewater contain many competing organic solutes and most of them may never be identified. Accordingly, a technique has been developed to predict the adsorption equilibria of known organic solutes onto granular activated carbon (GAC) in mixtures of unknown composition.

Ideal adsorbed solution theory (IAST) was used to describe the competitive interactions between adsorbates. Theoretical components (TCs) were used in IAST calculations to account for the competitive effects of the unknown mixture. The TC isotherm parameters and concentrations were determined by conducting a multicomponent isotherm of a tracer component which is added to the unknown mixture or singled out of the unknown mixture. Once the TC parameters were determined, the identical parameters were used to predict the competitive interactions between any known component and the unknown mixture. This procedure was verified experimentally for two activated carbons, three synthetic mixtures and a contaminated groundwater. The organic solutes were halogenated one and two carbon aliphatics which are common groundwater contaminants.     

An online method for estimation of degradable substrate and biomass in an aerated activated sludge process

The activated sludge process for degradation of organic matter is one of the main processes commonly used in biological wastewater treatment, and aeration in that process stands for a large part of the energy consumed in a plant. Hence, there have been many attempts to improve the operation of the activated sludge process using mathematical models of the process. The advanced models used has in general their origin in IWA (former IAWQ) activated sludge model no 1 (ASM1). Unfortunately, optimization w.r.t. discharge and economy is limited for municipal wastewater treatment plants because several of the most important variables; heterotrophic biomass, readily biodegradable soluble substrate, and slowly biodegradable substrate cannot be reliably measured online because of their complexity hiding behind their notation. With the predenitrifying WWTP in Göteborg having post nitrification in trickling filters as an example, we resolve this problem by deriving an observer that estimates these concentrations in the aerobic parts based on only the commonly available online measurements of oxygen, water flows, TSS concentration and supplied air. Based on control theory analysis and simulations it is concluded that estimation does not work for an activated sludge process with aeration in one stirred tank alone, but when the activated sludge process can be described by at least two tanks in series, with oxygen measurements in each tank, the estimates converge. A sensitivity analysis with respect to deviations in model parameters reveals that the derived estimator is also fairly robust to model errors.     

Application of multi-wavelength fluorometry for monitoring wastewater treatment process dynamics

Much of the methodology employed for characterizing wastewater and in modeling wastewater treatment processes employs off-line analysis. Off-line analysis is time consuming and not ideally suited to developing process control strategies. Clearly a rapid, inexpensive and reliable method suitable for following organic consumption and biomass production on-line would be very useful. In this study multiple excitation—multiple emission fluorometry was examined as a method for monitoring wastewater treatment processes. Results were first obtained for defined protein solutions and activated sludge to identify characteristic excitation and emission wavelength pairs. These results were then used to develop a rapid off-line assay for measurement of synthetic feeds consisting of protein substrates for batch aerobic and anoxic wastewater treatment processes and for on-line monitoring of cellular metabolic states in an anoxic process. Step-wise multiple regression and principal component analysis were employed for data analysis. The former was used to determine the most informative excitation and emission wavelength pairs while the latter was applied to reduce fluorescent spectra dimensions. Analysis of the batch kinetics suggests that this approach is valid and revealed some dynamic features of protein utilization and biomass accumulation under aerobic and anoxic conditions. A correlation was developed between COD-removal rates and the fluorescence signals in the two processes using fluorescent emission spectra rather than single signals. The data suggests that this multiple excitation—multiple emission fluorometry may be a suitable method for following wastewater and activated sludge dynamics and could be used as the basis for the development of expert system based biosensors.