Evaluation of a respirometric test method to determine the heterotrophic yield coefficient of activated sludge bacteria

The heterotrophic yield coefficient of activated sludge bacteria is an important parameter in the field of wastewater degradation kinetics and the determination of degradation kinetics of defined chemicals. With the help of easily biodegradable organic compounds like glucose and acetate the respiration kinetics of degrading activated sludge bacteria was studied. The results of the respiration analysis were transformed to examine the degradation and respiration kinetics of municipal wastewaters at different food to microorganism ratios (F/M ratios). It was proved that the heterotrophic yield coefficient of aerobically degrading activated sludge bacteria could reliably be determined and that the heterotrophic yield coefficient was independent of the F/M ratio over a wide range.     

Biodegradation of phenol in refinery wastewater by pure cultures of Pseudomonas aeruginosa NCIB 950 and Pseudomonas fluorescence NCIB 3756

The potential of microorganisms to catabolise and metabolise xenobiotic compounds has been recognised as a potentially effective means of toxic and hazardous wastes disposal. Phenol and its derivatives have long been recognised as some of the most persistent chemicals in petroleum refinery wastewaters, with high toxicity even at low concentrations. Biodegradation of these compounds has been recognised as a potential solution for their disposal owing to its cost effectiveness and simplicity. Two species of pseudomonas, P. aeruginosa and P. fluorescence, were studied for their biodegradation potential on phenol present in a refinery wastewater under a batch fermentation process. Phenol was successfully degraded by both species, and there was high positive correlation between phenol biodegradation and microbial growth. The maximum specific growth rate were obtained for both species from the Haldane model. The study revealed the high potential of these local strains, with P. aeruginosa being more effective, and the possibility of using them in bioremediation of petroleum refinery wastewaters.     

活性污泥法在工业废水处理中的应用进展

根据国外众多学者的研究成果，本文介绍了活性污泥法对食品加工、造纸、含金属、含酚、煤炭加工业、垃圾渗滤、化工、农药等废水的处理能力，应用范围及其在运行管理中应注意的有关事项。     

From agricultural use of sewage sludge to nutrient extraction: A soil science outlook

The composition of municipal wastewater and sewage sludge reflects the use and proliferation of elements and contaminants within society. In Sweden, official statistics show that concentrations of toxic metals in municipal sewage sludge have steadily decreased, by up to 90 %, since the 1970s, due to environmental programmes and statutory limits on metals in sludge and soil. Results from long-term field experiments show that reduced metal pollution during repeated sewage sludge application has reversed negative trends in soil biology. Despite this Swedish success story, organic waste recycling from Swedish towns and cities to arable land is still limited to only about 20 % of the total amount produced. Resistance among industries and consumers to products grown on land treated with sewage sludge may not always be scientifically grounded; however, there are rational obstacles to application of sewage sludge to land based on its inherent properties rather than its content of pollutants. We argue that application of urban organic wastes to soil is an efficient form of recycling for small municipalities, but that organic waste treatment from large cities requires other solutions. The large volumes of sewage sludge collected in towns and cities are not equitably distributed back to arable land because of the following: (i) The high water and low nutrient content in sewage sludge make long-distance transportation too expensive; and (ii) the low plant availability of nutrients in sewage sludge results in small yield increases even after many years of repeated sludge addition. Therefore, nutrient extraction from urban wastes instead of direct organic waste recycling is a possible way forward. The trend for increased combustion of urban wastes will make ash a key waste type in future. Combustion not only concentrates the nutrients in the ash but also leads to metal enrichment; hence, direct application of the ash to land is most often not possible. However, inorganic fertiliser (e.g. mono-ammonium phosphate fertiliser, MAP) can be produced from metal-contaminated sewage sludge ash in a process whereby the metals are removed. We argue that the view on organic waste recycling needs to be diversified in order to improve the urban–rural nutrient cycle, since only recycling urban organic wastes directly is not a viable option to close the urban–rural nutrient cycle. Recovery and recycling of nutrients from organic wastes are a possible solution. When organic waste recycling is complemented by nutrient extraction, some nutrient loops within society can be closed, enabling more sustainable agricultural production in future.     

Comparison of bioluminescence and nitrification inhibition methods for assessing toxicity to municipal activated sludge

The aim of this study was to compare two alternative toxicity assessment methods to determine wastewater toxicity and predict treatment plant process upsets. The toxicity of two synthetic organic compounds (triclosan and 4-n-nonylphenol), which are commonly detected in municipal wastewater, and municipal and industrial wastewaters with different heavy metals content were evaluated by the nitrification inhibition assay and bioluminescence toxicity test. Comparison between both assays confirmed that Vibrio fischeri is generally more sensitive than autotrophic bacteria, and, if not calibrated, the bioluminescence method tends to overestimate toxic effects on activated sludge biomass. The nitrification inhibition assay appears to predict plant process upsets more accurately. Both methods showed a significant toxicity decrease through treatment that could be partially attributed to the significant heavy metals removal obtained by primary and secondary treatment. A good correlation for the two assays was obtained, as indicated by a high correlation coefficient (r2 = 0.80).     

Enhanced biodegradation of azo dyes using an integrated elemental iron-activated sludge system: I. Evaluation of system performance.

The objective of this research is to evaluate an integrated system coupling zero-valent iron (Fe(0)) and aerobic biological oxidation for the treatment of azo dye wastewater. Zero-valent (elemental) iron can reduce the azo bond, cleaving dye molecules into products that are more amenable to aerobic biological treatment processes. Azo dye reduction products, including aniline and sulfanilic acid, were shown to be readily biodegradable at concentrations up to approximately 25 mg/L. Batch reduction and biodegradation data support the proposed integrated iron pretreatment and activated sludge process for the degradation of the azo dyes orange G and orange I. The integrated system was able to decolorize dye solutions and yield effluents with lower total organic carbon concentrations than control systems without iron pretreatment. The success of the bench-scale integrated system suggests that iron pretreatment may be a feasible approach to treat azo dye containing wastewaters.     

Fate of Terpene Compounds in Activated Sludge Wastewater Treatment Systems

ABSTRACT

Terpene-based cleaners are being widely used in industrial cleaning formulations because of their ability to replace suspected ozone-depleting chemicals such as 1,1,1-trichloroethane and 1,1,2-trichloro-1,2,2-trifluoroethane (CFC-113). Substitution of chlorinated solvents with ter-pene-based cleaners, however, is expected to result in increased discharges to wastewater from industrial operations. A pilot-scale study was conducted at the U.S. Environmental Protection Agency's (EPA) Test & Evaluation Facility in Cincinnati, OH, to quantify the fate of specific terpene compounds in the activated sludge wastewater treatment process. Biodegradation rates of terpenes were estimated from the difference between the influent terpene mass flow rates and the amounts volatilized to air, partitioned to waste sludge, and passed through the treatment process unchanged. Any chemical transformation of the terpene compounds studied was attributed to biodegradation.

Analytical methods were developed to determine ter-pene concentrations in aqueous and gaseous media. The fate of two common terpene compounds (d-limonene and terpinolene) were evaluated in three identical pilot-scale systems: (1) a system with a high target spike range (2–10 mg/L), (2) a system with a low target spike range (0.5–2 mg/L), and (3) a control system (no spike).

The study showed that the primary removal mechanism for the terpene compounds in the activated sludge process is biodegradation. Typically, greater than 90% of the mass of terpenes entering the aeration basin of the activated sludge process biodegrades to other compounds; volatilization from the reaction basin accounts for less than 10%, while loss to waste activated sludge and the secondary clarifier effluent accounts for less than 1%.     

Leachates from solid wastes: chemical and eco(geno)toxicological differences between leachates obtained from fresh and stabilized industrial organic sludge

The chemical and ecotoxicological characteristics of fresh and stabilized industrial organic sludge leachates were compared to obtain information regarding how the stabilization process can influence the ecotoxic potential of this industrial waste, which could be used for the amendment of degraded soil. Physicochemical analysis of the sludge leachates, as well as a battery of eco(geno)toxicity tests on bacteria, algae, daphnids, and higher plants (including Vicia faba genotoxicity test) and the determination of hydrolytic enzyme activity, was performed according to standard methods. The chemical comparison of the two types of leachate showed that the samples obtained from stabilized sludge had a lower organic content and higher metal content than leachates of the fresh sludge. The eco(geno)toxicological results obtained with aquatic organisms showed that the stabilized sludge leachate was more toxic than the fresh sludge leachate, both originating from the same industrial organic sludge sample. Nevertheless, phytotoxicity tests carried out with a reference peat soil irrigated with stabilized sludge leachate showed the same toxicity as the fresh sludge leachate. In the case of the industrial solid organic sludge studied, stabilization through a biodegradation process promoted a higher metal mobility/bioavailability/eco(geno)toxicity in the stabilized sludge leachate compared to the fresh sludge leachate.     

An activated sludge process to reduce the pollution load of a dye-industry waste

A laboratory-scale activated sludge process was developed to reduce the pollution load of a dye-industry waste, containing aniline, phenol, methyl violet and rhodamine B as its major components. The waste exerted an organic load of 5576 mg litre(-1) as the chemical oxygen demand (COD), of 896 mg litre(-1) as total organic carbon (TOC), and had a 31.5 mg litre(-1) phenol content. A microbial sludge, capable of growing on the waste, was developed from cattle dung, adapted to the waste and used as a bioinoculum for the process. This resulted in reductions of 60% in COD, 37% in TOC, and 92% in phenol content, and a decrease in optical density of the colour of the waste from an initial 0.915 to 0.360 at 580 nm. Microorganisms isolated from sludge were identified as Pseudomonas alcaligenes and P. mendocina.     

Efficacy and reliability of upgraded industrial treatment plant at Porto Marghera, near Venice, Italy, in removing nutrients and dangerous micropollutants from petrochemical wastewaters

Chemical and petrochemical wastewaters contain a host of contaminants that require different treatment strategies. Regulation of macropollutants and micropollutants in the final discharge from industrial wastewater treatment plants (WWTPs) have become increasingly stringent in recent decades, requiring many WWTPs to be upgraded. This article presents an analysis of a WWTP treating petrochemicals in Porto Marghera, Italy, that recently was upgraded following legislative changes. Because of strict legal limits for macropollutants and micropollutants and a lack of space necessary for a full-scale WWTP overhaul, the existing activated sludge tank was converted into a membrane biological reactor. The paper presents experimental data collected during a five-month investigation showing the removal rates achieved by the upgraded plant for macropollutants (particularly nitrogen compounds) and micropollutants (heavy metals and organic and inorganic toxic compounds).     

The effect of wastewater cations on activated sludge characteristics: effects of aluminum and iron in floc.

Wastewater samples collected from seven wastewater treatment plants (WWTPs) were characterized to assess the impacts of wastewater cations on the activated sludge process. The cations included in this study were sodium (Na+), potassium, ammonium, calcium, magnesium, aluminum (Al), and iron (Fe). Among the selected cations, Al and Fe were of most interest to this study because their role in bioflocculation has not been extensively studied and remains largely unknown. The data showed that WWTPs contained highly varying concentrations of Na+, Al, and Fe in the wastewater and that these cations were responsible for differences between WWTPs as to sludge dewatering rates and effluent quality. In general, a high influent Na+ concentration caused poor sludge dewatering and effluent characteristics. However, when sufficient Al and Fe were present in floc, the deleterious effects of Na+ were offset. The data associated with Al further revealed that waste activated sludge with low Al contained high concentrations of soluble and colloidal biopolymer (protein + polysaccharide), resulting in a high effluent chemical oxygen demand, high conditioning chemical requirements, and poor sludge dewatering properties. These results suggest that Al will improve activated sludge effluent quality by scavenging organic compounds from solution and binding them to floc.     

Application of reutilization technology to calcium fluoride sludge from semiconductor manufacturers

Glass ceramics were prepared from mixtures of wastes generated from refining of waste glass and semiconductor industrial wastewater sludge. The aim is then indeed to study the possible use and effects of integrating calcium fluoride (CaF2) as present in semiconductor wastewater sludge in the silica (glass) melts. CaF2 sludge was blended with a conditioner according to characteristics of the target. Calcium oxide-silicon dioxide-aluminum oxide system glass ceramics have relatively high melting points. Addition of CaF2 sludge to fluxes can significantly reduce the melting point and hence improve the kinetics of the reactions. CaF2 sludge and waste glass were co-melted in various ratios to elucidate their interactions at various heating temperatures. The results indicate that the lowest melting temperature was 1163 degrees C, obtained for the CaF2 sludge-waste glass mixture at a ratio 6:4 (wt:wt), which is significantly lower than that of CaF2 sludge (1378 degrees C). The benefits of using melting to dispose of sludge are the reduction of waste and the fixation of heavy metals. Heat treatment was used to convert the obtained glass into glass ceramics. Heavy metal leaching tests revealed that melting conditions lowered the heavy metal concentrations in the leachate to an order of magnitude lower than that in the sludge. Consequently, industrial sludge can be safely used as a fine aggregate material for a potentially wide range of construction applications.     

Development of a three-stage system for wastewater toxicity monitoring: a design and feasibility study.

A three-stage system was developed to automate a batchwise toxicity testing protocol designed for assessing wastewater toxicity to activated sludge. The three-stage system used the luminescent bacterium Shkl. The three stages were cell storage, cell activation, and continuous toxicity testing. Shkl cells were stored in a bioreactor at 4 degrees C when the system was not in use and activated in another bioreactor for use in toxicity tests conducted in a continuous manner. The system could quickly be switched between the "off" and "on" modes, and operation of the system was easy. The stability of the system, in terms of cell density and bioluminescence in the storage and activation bioreactors, and the response of the activated cells to a metal and an organic toxicant were studied. The feasibility of the system design was demonstrated by simulating zinc toxicity episodes in synthetic wastewater. The needs for further modifications and improvements of the system were discussed.     

Removal of organic and nitrogen and molecular weight distribution of residual soluble organic from entrapped mixed microbial cells and activated sludge processes.

The simultaneous removal of organic and nitrogen and molecular weight distribution (MWD) of residual soluble chemical oxygen demand (RSCOD) in final effluent were investigated using entrapped mixed microbial cells (EMMC) and conventional activated sludge processes. Two different types of processes using EMMC carriers demonstrated better organic and nitrogen removal performance because of the high solids retention time (SRT) compared with the activated sludge process. Regarding the RSCOD, the longer SRT process (EMMC) was affected by reducing the hydraulic retention time, resulting in the increase of high-molecular-weight materials. On the other hand, reducing the aeration period had significantly affected the MWD in the shorter SRT process (activated sludge), resulting in an increase of low-molecular-weight materials.     

Petroleum refinery stripped sour water treatment using the activated sludge process

A pilot study was performed over 91 days to determine if the activated sludge process could treat a segregated stripped sour water (SSW) stream from a petroleum refinery. The study was performed in two periods. The first period was terminated after 19 days, as a result of excessive sludge bulking. The elimination of sludge bulking during the 70-day second period is attributed to operational changes, which included aerating the influent to oxidize reduced sulfur, adjusting the influent pH, and adding micronutrients to satisfy biological requirements. The pilot plant provided a chemical oxygen demand (COD) removal of up to 93%. Nitrification was achieved, with effluent ammonia values < 1 mg-N/L. These results indicate that direct treatment of SSW with the activated sludge process is possible and has direct application to full-scale petroleum refinery wastewater plant upgrades.     

Development of a packed-bed reactor for the recovery of metals from industrial wastewaters

Affinity separation is becoming well established for the purification and recovery of metals from industrial wastewaters. Although the method has been successfully applied on a bench-scale, there is a need for reaction engineering studies to scale-up the process for use in large-scale wastewater purification and recovery of valuable metals. In this study, a pilot-scale packed-bed reactor has been developed in order to investigate influences of process parameters and their interactions on the recovery of metals from process wastewaters using diatomaceous material. The material was formed into a packed configuration to provide a high adsorbent area-to-aqueous solution volume ratio. Activated carbon and ion-exchange resin were tested for comparison. The results obtained show that the flow-rate, residence time, metal concentration loading and packed-bed geometry significantly influenced the efficiency of the reactor system metal recovery and have to be considered in the design of large-scale system. An optimum residence time of 2 h was found to give metal recovery capacities of 60%, 76% and 80% for the ion-exchange resin, diatomaceous material and activated carbon, respectively, which confirmed the bench-scale studies. The sequestered metals were efficiently eluted from the diatomaceous material using different elution solutions for different metals. The selectivity of the adsorbent for specific metals can be manipulated on the uptake and elution sides of the process. The study also revealed that diatomaceous material can be regenerated and used many times over, just like conventional adsorbents or ion-exchange resins in process wastewater purification as well as in metal recovery processes. The application of the packed-bed reactor using the locally available diatomaceous material is therefore recommended for economical and cost-effective small-scale purification and recovery of metals from industrial wastewaters loaded with metals in Nigeria.     

堆肥法处理含油污泥研究进展

含油污泥是炼油厂和石油化工厂的日产固体废弃物 ,是当前石化行业所面临的污染问题。本文给出了近期国内外对含油污泥的处理方法 ,并对堆肥法处理含油污泥进行了综述。含油污泥的堆肥处理需提供氧气、菌种和营养 ,为保持油泥的疏松状态 ,还需加入填充剂。本文对高速生物反应器的结构、运行、调控进行了详细介绍 ,并从经济核算角度指出了其运营可行性     

Anaerobic codigestion of municipal, farm, and industrial organic wastes: a survey of recent literature.

Codigestion of organic wastes is a technology that is increasingly being applied for simultaneous treatment of several solid and liquid organic wastes. The main advantages of this technology are improved methane yield because of the supply of additional nutrients from the codigestates and more efficient use of equipment and cost-sharing by processing multiple waste streams in a single facility. Many municipal wastewater treatment plants (WWTPs) in industrialized countries currently process wastewater sludge in large digesters. Codigestion of organic wastes with municipal wastewater sludge can increase digester gas production and provide savings in the overall energy costs of plant operations. Methane recovery also helps to reduce the emission of greenhouse gases to the atmosphere. The goal of this literature survey was to summarize the research conducted in the last four years on anaerobic codigestion to identify applications of codigestion at WWTPs. Because the solids content in municipal wastewater sludge is low, this survey only focuses on codigestion processes operated at relative low solids content (slurry mode). Semi-solid or solid codigestion processes were not included. Municipal wastewater sludge, the organic fraction of municipal solid waste, and cattle manure (CAM) are the main wastes most often used in codigestion processes. Wastes that are codigested with these main wastes are wood wastes, industrial organic wastes, and farm wastes. These are referred to in this survey as codigestates. The literature provides many laboratory studies (batch assays and bench-scale digesters) that assess the digestibility of codigestates and evaluate the performance and monitoring of codigestion, inhibition of digestion by codigestates, the design of the process (e.g., single-stage or two-stage processes), and the operation temperature (e.g., mesophilic or thermophilic). Only a few reports on pilot- and full-scale studies were found. These evaluate general process performance and pretreatment of codigestates, energy production, and treatment costs.     

Oxidation-reduction potential changes in aeration tanks and microprofiles of activated sludge floc in medium- and low-strength wastewaters.

Real-time control of aeration tank operation is key to high-efficiency pollutant removal and energy savings. One of the aims of this study was to examine the potential for using redox potential (oxidation-reduction potential [ORP]) to indicate wastewater quality online in aeration tanks treating medium (chemical oxygen demand [COD] of 70 to 150 mg/L) and low (COD of 15 to 30 mg/L) pollutant-concentration wastewaters. The field-scale data provide a good relationship between ORP values and nutrient removal along the length of the aeration tanks. The ORP values increased dramatically as organic matter was removed along the aeration tanks, indicating the improvement of the bulk liquor redox status. Dissolved oxygen higher than 1.0 mg/L was necessary for good biodegradation and improvement of the liquid redox status. Nitrification occurred at higher ORP values (380 to 420 mV) than was the case for organic substrate oxidation (250 to 300 mV). The microprofiles obtained from microelectrode measurements substantiate the heterogeneity of the microbial processes inside activated sludge flocs. Because of microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the top layer (0.1 to 0.2 mm) of the activated sludge aggregate present in medium-strength wastewater, with an anoxic zone dominating inside the flocs. When dissolved oxygen in the bulk water was higher than 4.0 mg/L, the anoxic zone inside the floc disappeared. At low wastewater pollutant concentrations, the ORP and dissolved oxygen inside the activated sludge aggregates were higher than those from medium-strength wastewater. The prospect of using ORP as an online control approach for aeration tank operation and the potential reasons for activated sludge floc size varying with pollutant strengths are also discussed.     

Persistent organic pollutants (POPs) in the conventional activated sludge treatment process: model predictions against experimental values

The FATE and treatibility estimator (FATE) model, developed by the United States Environmental Protection Agency was used for the prediction of the FATE of 26 persistent organic pollutants (POPs), i.e. 7 PCBs and 19 organochlorine compounds (OCs), during the conventional activated sludge treatment process applied in the waste water treatment plant (WWTP) of Thessaloniki, Greece. The removal rates predicted by the model for the primary and the secondary treatment stages were found to differ substantially from those experimentally measured. When the overall treatment was considered, the differences between measured and model predicted removals were within acceptable limits of confidence. Possible reasons that might cause deviations from experimental values were suggested to be the wastewater content in dissolved organic carbon (DOC), and/or the low concentrations of POPs in untreated wastewater.