A new rapid method for determining sludge activity

One of the most reliable methods for characterizing an activated sludge is by measurement of its activity. The measuring principle of the method developed is based upon the determination of glucose activity of the activated sludge. The activated sludge sample is continuously aerated in a reactor and glucose standard solution is given to it. The glucose uptake in the activated sludge system is measured by a glucose selective electrode. The sludge activity is calculated on the basis of the reaction time required for the 50% decomposition of the glucose. Only the change of dissolved oxygen concentration of the sample interferes the measurement. This interference is eliminated by the measurement of dissolved oxygen. The electrical response of glucose electrode is corrected with that of the oxygen electrode. The method is selective, the reproducibility of it is better than 10%.     

Viability of microbial mass in compartmentalised single activated sludge process

Investigations were carried out for steady-state conditions on laboratory-scale model of an anaerobic-aerobic-anaerobic-aerobic configuration of the activated sludge process, for hydraulic detention time of 9.13 h and sludge age of 9, 16.4 and 28.3 days. Data was obtained on volatile suspended solids (MLVSS), adenosine triphosphate (ATP), oxygen uptake rate (OUR) and relative dehydrogenase activity (RDA) on the laboratory model and the extended aeration biological treatment unit at the ARAMCO treatment plant in Dhahran. A mathematical model was obtained based on the laboratory data, using a calibration method to estimate MLVSS for given values of OUR, RDA and ATP. Regression coefficients for MLVSS and OUR. MLVSS and RDA and MLVSS and ATP were determined.It was found that the mathematical model obtained does not adequately describe the inter-relationship between various parameters. The inter-relationship is a function of operational conditions occurring in the plant and too complex to be described by a mathematical model. MLVSS offers the best estimate and cannot be related by an equation with OUR, ATP and RDA.     

Micronutrient supplements for optimisation of the treatment of industrial wastewater using activated sludge

The process performance and metabolic rates of several samples of activated sludge which were dosed with micronutrient supplements have been compared in this study. Six trace metals and six vitamins were used as chemical additives dosed into the mixed liquor. It was confirmed experimentally that a wastewater stream from a chemicals manufacturing plant did not contain a sufficient supply of micronutrients for efficient biological treatment. This was concluded from the observation that control sludge batches (receiving no micronutrient supplements) attained an average chemical oxygen demand (COD) removal rate of 1.94 kg COD kg MLSS⁻¹ d⁻¹. Dosing micronutrients into the mixed liquor produced COD removal rates of up to 2.24 kg COD kg MLSS⁻¹ d⁻¹. Some of the supplements increased the metabolic rate of the sludge while some decreased it, indicating a range of stimulatory and inhibitory effects. Complex interactions between micronutrients that were dosed simultaneously were evident. Several positive effects led to the conclusion that micronutrient supplements have the potential to optimise the process performance of activated sludge plants treating industrial wastewater.     

活性污泥法中引起丝状菌污泥膨胀的因素

活性污泥法是采用最普遍的污水处理工艺,而丝状菌污泥膨胀则是该工艺污水运行中易发生、危害大的问题.介绍了近30 年来国际上关于丝状菌污泥膨胀的最新研究成果,分析了影响丝状菌污泥膨胀的主要因素.     

The Two-Stage Moving-Bed/Activated-Sludge Process: An Effective Solution for High-Strength Wastes

The paper describes a moving-bed bioreactor which was used as the first stage of a two-stage process to provide an effective and simple means of reducing the biochemical oxygen demand of a wastewater prior to further treatment in a conventional second-stage activated-sludge plant.
At Corby, a scheme was required to (a) meet the requirements of a more stringent effluent consent and (b) provide capacity for further anticipated growth in industrial effluent loads. The original works comprised conventional primary sedimentation tanks, biological filters and humus tanks, followed by an activated-sludge oxidation ditch and further settlement tanks. A pilot plant has been in operation at Corby for two years, and the results were used to design a moving-bed bioreactor to replace the existing filters.
At Pyewipe, a new coastal treatment plant was required and, following the change in status from a 'high natural dispersion area &, a 'normal' programme was initiated to achieve the required completion date. A value-management workshop was held which identified the two-stage moving-bed bioreactor/activated-sludge process, and a pilot plant was operated for eighteen months. A full-scale plant is now under construction and incorporates a number of innovative features.     

临沂大学全地下式污水处理工程CAST工艺的设计

临沂大学污水处理厂采用循环式活性污泥法(CAST)处理校内及学校附近居民小区污水,用机械浓缩脱水一体化设备处理剩余污泥,其主体构筑物CAST生物池为鼓风微孔曝气式,出水达到了《城镇污水处理厂污染物排放标准》(GB18918—2002)的一级A标准。该污水处理厂是一座规模较大的全地下式污水处理厂,工艺先进、构筑物及设备选型合理、自动化程度高。     

Phosphorus removal in the activated sludge process

The results from this research suggest that both calcium phosphate precipitation and enhanced biological uptake play a role in phosphorus removal in the activated sludge process when a non-nitrifying, anaerobic-aerobic system is used to treat a low calcium wastewater. The primary removal mechanism was found to be biological uptake, as calcium phosphate precipitation accounted for only 15–27% of the total phosphorus removed. Calcium phosphate precipitation in the aerobic unit was enhanced because of the pH increase in that reactor. This was the result of low CO₂ production (indicated by low specific oxygen uptake values) and intense aeration which caused excessive CO₂ stripping in the aerobic unit     

Biological treatment of low temperature carbonization wastewater by activated sludge process—A case study

This paper outlines the compositional characteristics of wastewater from a low temperature carbonization (LTC), plant manufacturing domestic coke, generating tar and light oil. Wastewater characteristics from this plant show the presence of a variety of pollutants like phenols, ammonia, cyanide, sulphide and thiocyanate in appreciable concentration owing to the absence of byproduct recovery operations. Under suitable conditions, biological treatment of LTC wastewater in a two stage activated sludge process (ASP) mainly results in good removal of BOD (95%) and COD (78%). Concentrations of different phenols and their fate in these treatment units show that the phenols except pyrogallol can be removed efficiently. Ammonia cannot be stabilized to nitrite or nitrate even after maintaining a high sludge retention time (SRT) in the bioreactors. Cyanide removal in these units is very poor. Microbiological status of these units reveals that most of the active biomass is comprised of phenol-utilizing organisms. The system constants for biological unit operations for ASP, like oxygenation capacity of LTC wastewater (a = 0.50 and B = 0.36) and biokinetic constants (Y = 0.13, k_d = 0.12 d⁻¹, μ_max = 0.59 d⁻¹ and k_s = 88.25 mg 1⁻¹), have been evaluated.     

Perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in sewage treatment plants

In this study, the concentrations of PFOS and PFOA in the biological units of various full-scale municipal sewage treatment plants were measured. Samples of influent, primary effluent, aeration tank effluent, final effluent and grab samples of primary, activated, secondary and anaerobically digested sludge were collected by 5 sampling events over one year. The two sewage treatment plants (STPs) selected for this study include plant A receiving 95% domestic wastewater and plant B receiving 60% industrial wastewater and 40% domestic wastewater. PFOS and PFOA were observed at higher concentration in aqueous and sludge samples in plant B than that of plant A. Mass flow of PFOS increased significantly (mean 94.6%) in conventional activated sludge process (CAS) of plant B, while it remained consistent after the secondary treatment in plant A. Mass flow of PFOA increased 41.6% (mean) in CAS of plants A and B and 76.6% in membrane biological reactor (MBR), while it remained unchanged after the treatment of liquid treatment module (LTM). Our results suggest that mass flow of these two compounds remains consistent after treatment of activated sludge process operating at short sludge retention time (SRT). Seasonal variations of PFOS in concentrations of raw sewage were found in plant A, while PFOA did not have significant seasonal variation in both plants A and B.     

Feedforward control of a wastewater plant

A feedforward control strategy to compensate for disturbances in the applied biological load to the activated sludge plant was designed. This strategy was generated from Laplace-domain transfer function models predicting the dissolved oxygen concentration at the end of the aeration tank from the applied biological load and the air flowrate. In producing these models, the Luggage Point Wastewater Treatment Plant was used to obtain plant data. After conducting a series of computer simulation tests, the improvement in performance using the new control scheme compared to the existing dissolved oxygen feedback controller resulted in a 20% reduction in air flowrate. It is estimated the new strategy would give a payback period of less than 15 months.     

The electrolytic respirometer—II Use in water pollution control plant laboratories

The electrolytic respirometer provides a direct and continuous measure of oxygen uptake in a wastewater sample. The principal advantages of this method are that (1) little or no dilution of the sample is required, (2) larger and more representative samples can be analyzed, (3) tests can be run for days or weeks without interruption, (4) the equipment is simple to operate, (5) no titrations are required, and (6) BOD can be measured with significantly greater precision than with other methods.

The use of electrolytic respirometers in research laboratories and water pollution control plant and industrial laboratories demonstrated that the method is technically and economically justified for plant control and evaluation purposes. This method was well received by treatment plant operators and laboratory analysts when used for purposes ranging from routine measurement of BOD to investigating the treatability of industrial wastes.     

Oxygen uptake rates for determining microbial activity and application

The method presented involves using the oxygen uptake rates of activated sludges for determining the microbial activity and viability. The microbial activity correlates well with the substrate reduction first order rate constant. K₁, determined in batch operations, and with the specific substrate utilization rate, q, of steady state operations. The microbial viability determined based on respiratory activity would result in slightly higher values than other means such as plate counting, since some of the respiratory activity is contributed by nonviable yet active cells. The extent of respiratory activity attributed to the nonviable cells increases as the biological solids retention time increases (or net growth rate decreases). Since the loss of ability of multiplication is not necessarily associated with loss of biochemical activity, the viability determined by the respiratory activity would represent more realistically the activity of microbes and thus is suggested as the preferred technique.     

太原市城南污水处理厂污泥培养驯化及调试

以太原市城南污水处理厂为例,介绍了该污水处理厂的污水处理流程及所采用的改良AAO生物处理工艺,通过采用直接培养活性污泥的方法,对城南污水处理厂的污泥进行了培养驯化,并针对调试过程中出现的问题提出了相应的解决措施,以达到净化污水水质的目的。     

Conditioning of wastewater sludge using freezing and thawing: role of curing

Freeze/thaw (F/T) treatment is an efficient pre-treatment process for biological sludges. When bulk sludge was frozen, tiny unfrozen regimes in the ice matrix were continuously dehydrated by surrounding ice fronts, termed as the “curing stage”. This work demonstrated that the F/T treatment could not only enhance sludge dewaterability, but also solubilize organic matters from sludge matrix. Most enhancement of sludge dewaterability was achieved during bulk freezing stage, with the waste activated sludge more readily dewatered than the mixed sludges after treatment. Conversely, the freezing stage released only limited quantities of organic matters to liquid. Conversely, the curing contributed mostly on chemical oxygen demand (COD) solubilization and NH₃-N release. The crystallization of intra-aggregate moisture was claimed to damage cell membranes so to release intracellular substances to surroundings. The F/T treatment with sufficient curing is advised to effectively condition biological sludge as the feedstock of the following anaerobic digestion process.     

Power economy characteristics of an activated sludge aeration tank

The air feed rate to meet a given oxygen uptake rate in the activated sludge aeration tank was expressed by using the concept of the air diffuser performance, previously proposed by the present authors. Using the relationship between the BOD removal and the oxygen uptake rate, a procedure to predict the power economy, which is defined as the amount of BOD removed per unit power consumption of the air feeding, and the effluent quality of the activated sludge process under various operating conditions was presented. The effect of operating parameters in the tank; the MLSS concentration; the hydraulic retention time and the BOD loading on the power economy and the effluent quality were extensively evaluated. The results calculated by the proposed procedure were compared with the statistic data of operating conditions in the municipal wastewater treatment plants in Japan. A method to improve the effluent quality while maintaining a high power economy was also discussed.     

Powdered activated carbon in an activated sludge treatment plant

Addition of powdered activated carbon (PAC) to the aeration basin of an activated sludge treatment plant fed with dye-works waste waters increases the purifying capacity of the plant: removal efficiency rises from 55.8 to 75.6% (COD) and from 78 to 98.5% (BOD₅) and the nitrification-denitrification capacity of the system also increases.The sludge growth parameters and the kinetic constant of biological oxidation were determined on the plant with and without PAC. The addition of PAC decreased overall sludge growth rate and the auto-oxidation factor, but increased the biological removal rate of the substrate by about one order of magnitude.     

Inhibition coefficient (Ki) determination in activated sludge

A method of measurement of the inhibition coefficient, K_i, of chemicals within the activated sludge has been proposed. It makes possible the objective determination of the influence of non-competitive inhibitors on the reaction rate by means of simple respiration rate measurements with the application of a dissolved oxygen meter. The values of K_i for chromium Cr⁶⁺, for cyanide CN^? and for two pesticides—DDVP and des-methyl DDVP was determined.     

Enhanced uptake of phosphorus by activated sludge-effect of substrate addition

Studies were undertaken to examine the effect of substrate addition upon the release and subsequent uptake of phosphorous by a biological wastewater treatment laboratory scale system.A train of six reactors were fed at a rate of 16 ml min⁻¹ raw wastewater using a sludge recycle ratio of 0.75 (12 ml min⁻¹). The first two reactors were simply stirred (anoxic) without the addition of air and the remaining four were aerated with excess air.Various substrates were added to the first reactor (anoxic) at different concentrations. It was determined that all the short chain substrates tested enhanced the release of phosphorus in the anoxic stages and subsequently led to increased biological uptake (removal) of phosphorus. The substrates tested included sodium acetate, acetic acid, butyric acid, ethanol and methanol.It was determined that 30 mg l⁻¹ sodium acetate was the optimum dose for biological release and uptake of phosphorus and the addition of any greater concentration had marginal effect on the ultimate removal of phosphorus.The effect of these substrates showed some specificity regarding phosphorus release, with butyric acid causing the greatest release and sodium acetate the least. However as far as phosphorus uptake (removal) was concerned, this phenomenon of substrate-specificity was less significant. For all substrates, effluent phosphorus concentration was within ± 1 mg l⁻¹ with an approximate mean concentration of 1 mg l⁻¹ residual.Phosphorus released (approx. 14 mg l⁻¹) at higher temperature (29°C) was 75% greater than at the lower temperature (24°C). Similarly the final residual phosphorus at 29°C was 33% lower than at 24°C.     

Toxicity assessment of common xenobiotic compounds on municipal activated sludge: comparison between respirometry and Microtox

The toxicity of four xenobiotic compounds 3,5-dichlorophenol, formaldehyde, 4-nitrophenol and dichloromethane, representative of industrial wastewater contaminants was evaluated by a simple respirometric procedure set up on the basis of OECD Method 209 and by the Microtox bioassay. Very good reproducibility was observed for both methods, the variation coefficients being in the range of 2-10% for the respirometric procedure and 6-15% for Microtox, values that can be considered very good for a biological method. Comparison of EC(50) data obtained with the two methods shows that in both cases 3,5-dichlorophenol is more toxic than other compounds investigated and dichloromethane has a very low toxicity value. Intermediate EC(50) values were found for the two other chemicals, formaldehyde and 4-nitrophenol. Moreover, the Microtox EC(50) values are generally lower (except for dichloromethane) than the respirometric ones: these differences could be explained by the fact that the Microtox method uses a pure culture of marine species and, therefore, should not necessarily be expected to behave like a community of activated sludge bacteria. In conclusion, both methods can be usefully applied for toxicity detection in wastewater treatment plants but it is advisable to take into account that Microtox is more sensitive than respirometry in estimating the acute toxicity effect on the biomass operating in the plant.     

SBR工艺系统中污泥的TTC-ETS活性变化

通过检测SBR工艺系统的TFC-ETS活性，研究了污泥生物活性的变化规律和活性状况。试验结果表明：TIC-ETS活性可以有效地表征SBR系统的生化反应进程；有机物降解、硝化和反硝化阶段的生物活性依次降低，运行条件并未明显影响到SBR系统的TFC-ETS活性变化规律，但影响到TIC-ETS活性曲线上标志不同反应阶段的特征点出现时间和各阶段的平均生物活性；TFC-ETS活性与DO、ORP和pH值之间存在良好的相关关系。