Activated Sludge Process Response to Variable Inputs of Volatile Organic Contaminants

Melcer, Henryk; Nutt, Stephen G.; Monteith, Hugh

doi:10.2166/wst.1991.0434

Cited by 10 publications

(5 citation statements)

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“…These compound characteristics have been found to contribute to recalcitrant behavior during aerobic biodegradation (Kobayashi andRittmann, 1982, andSahmzyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA et al, 1986). Melcer et al (1991) reported similar behavior for these compounds in bench-scale reactors. The reduced level of biodegradation along with enhanced liquid-gas phase partitioning as indicated by the relatively high Henry's law constants for these compounds likely contributed to the preferential loss by stripping.…”

Section: Resultsmentioning

confidence: 66%

“…The dosing solution was pumped at a rate to attain the target concentration for each compound in the aeration basin influent presented in Table 2. The selection of target concentrations was based upon actual field sampling of raw sewage at different locations in Ontario (Bell et al, 1988, andMelcer et al, 1991). During dosed tapwater and wastewater experiments, the primary effluent was dosed for a period of 26 hours, which represented approximately 4 HRTs of the aeration basin and secondary clarifier, to attain steady-state conditions.…”

Section: Description Of Wastewater Treatment Plants the Behavior Oimentioning

confidence: 99%

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Fate of volatile organic compounds in municipal activated sludge plants

Parker¹,

Thompson²,

Bell³

et al. 1993

Water Environment Research

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The fate of volatile organic compounds (VOCs) in municipal activated sludge plants was investigated at pilot and full scale. More than 80% of the mass flow of nonchlorinated compounds was observed to be biodegraded while less than 20% was removed by stripping. Conversely, 46% of the mass flow of chlorinated compounds was biodegraded and 47% was removed by stripping. Adsorption of VOCs onto waste sludge was not a significant removal mechanism. The pilot plant employed was found to effectively emulate the liquid‐gas phase partitioning and overall compound removals observed in a full‐scale plant. Little difference in liquid‐gas phase partitioning was observed for coarse and fine pore diffusers in spite of differing mass‐transfer characteristics as demonstrated by oxygen‐transfer measurements. This implies that equilibrium between the liquid and gas‐phase concentrations was achieved with both diffuser types. Stripping of VOCs was observed to increase with airflow; however, the extent of stripping increased at a declining rate.

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Section: Resultsmentioning

confidence: 66%

Section: Description Of Wastewater Treatment Plants the Behavior Oimentioning

confidence: 99%

Fate of volatile organic compounds in municipal activated sludge plants

Parker¹,

Thompson²,

Bell³

et al. 1993

Water Environment Research

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“…The above feature of the SBR is attributed to dilution because the retained wastewater comprises~40% of the reactor liquid volume, thus decreasing the ambient concentrations to below inhibition threshold levels. Melcer et al (1991) also reported that changes in influent concentrations of toluene and xylene to an activated sludge system from 15 to 500 p,g/L resulted in a rapid initial increase in effluent concentrations to a peak followed by a decline to a low level close to the original level. observed that doubling of the influent phenol concentration from 500 to I 000 mg/L was attenuated by the system but further increase to 2000 mg/L resulted in system failure.…”

Section: Discussionmentioning

confidence: 96%

Modeling of sequencing batch reactors treating inhibitory and noninhibitory wastewaters

Nakhla¹,

Ahmed²,

Farooq³

1997

Water Environment Research

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The mathematical model is developed based on the following assumptions: the reactor is completely mixed with aeration and mixing during react and fill periods; all nutrients are in abundance and only one substrate, whose use follows Monod-type kinetics, is growth limiting; the kinetic constants do not vary from one period to another, i.e., the pertinent parameters during the react period are also applicable for the fill period; and the required solids residence time (SRT) is maintained by wastage of the appropriate volume of mixed liquor at the end of the react period.Based on the aforementioned assumptions, following are the mass balance equations for microbial cell and substrate concentration during fill and react periods, during the nth cycle of operation. It is worth mentioning that the subscript n -I appearing in the fill equations denotes the (n -I )th cycle.Fill period. During fill period, the reactor receives raw wastewater and therefore the volume varies with time and it can be expressed as (Dennis and Irvine, 1979) the mathematical description of the SBR system is not fully developed, and because of the unsteady nature of the SBR treatment, it is quite difficult to formulate a complete mathematical model for the system (Irvine and Ketchum, 1989). However, mathematical expressions that partially describe the SBR operation have been reported in the literature since late 1970s. Dennis and Irvine (1979) developed substrate mass balance equations for the fill and react periods, and later Irvine and Ketchum (1989) presented a more general formulation of SBR modeling. Hsu (1986) presented mathematical expressions for bacterial growth and substrate utilization during the react period using Monod kinetics. Furthennore, although inhibition kinetics have been incorporated in models of continuous flow systems Chudoba et at., 1989), modeling of SBRs treating biologically inhibitory wastewaters is still lacking. Therefore, for improved understanding of the performance and design of the SBR, the development of a rigorous mathematical model of the process is crucial. The purpose of this paper is to develop a mathematical model for the SBR system and use it to analyze impact of process variables on the treatment of biodegradable noninhibitory and inhibitory wastewaters and thus assess inhibition effects, as well as for prediction purposes.ABSTRACT:A mathematical model for sequencing batch reactors (SBR) that takes into account fill and react periods was developed and tested against experimental data from the literature. The Monod equation was used to describe microbial growth kinetics. The proposed model predicts the time dependent microbial cell and substrate concentrations during SBR treatment of wastes. A numerical method was used to solve the governing model equations which comprised nonlinear unsteadystate ordinary differential equations. Model simulations highlighted the importance of feed rate as a major operating parameter. For biodegradable wastes and low strength inhibitory wastes, an instantaneous fill is opt...

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“…Data indicated that a relatively long sludge retention time, between 10 and 20 d, was required for maximum removal of PCP, and that a background level of PCP in the influent was required to maintain a PCP degrading population. Further studies using laboratory-scale units with an aeration basin of 5 1 capacity and a clarifier of 4 7 1 capacity were carried out to determine the treatability of variable amounts of volatile organic chemicals including chloroform, tetrachloroethylene, trichlorethane, toluene, xylene, and five heavy metals (Melcer et al, 1991). It was concluded that different mechanisms were responsible for the removal of short-term variable inputs of volatile organic compounds.…”

Section: Continuous Simulation Testsmentioning

confidence: 99%

Treatability, Toxicity and Biodegradability Test Methods

Kilroy

Gray

1995

Biological Reviews

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1. This review confirms that treatability and biodegradability test methods have been cited extensively in the literature. It is clear that the method selected depends on the specific objectives of the test, i.e. the determination of whether a substance is toxic, biodegradable or treatable. Factors that have to be considered when selecting the test methods are the cost of performing the test, the time and resources involved, and the accuracy required. It often appears that more extensive simulation studies are required after initial screening tests have been performed. 2. Many of the enzyme and bacterial growth tests which have been developed for monitoring or screening of toxicants and their persistence in water and wastewaters have been reviewed. Most of these tests are rapid, inexpensive, and reproducible. Most of the biochemical and microcalorimetric approaches, although promising, are still in their infancy as regards toxicity testing. Therefore, biological testing still appears to be most suitable for routine assessment. 3. Micro-organisms are particularly suitable for use in toxicity testing of chemicals as they are inexpensive to culture, have rapid growth rates, and usually provide reproducible results (Vaishnav & Korthals, 1990). Many bioassays have been developed to evaluate the toxicity and treatability of municipal and industrial effluents. Numerous single species tests have been recommended by several authors (Dutka et al., 1983; Beaubien et al. 1986). Such approaches are mainly based on the belief that, by selecting the most sensitive species and by using appropriate factors to allow for variability not included in the test, the highest levels of biological organization will be adequately protected. Single species tests are now quite well established, and when properly used, are easy to analyse and quantify. However, it has been pointed out (Levin, 1984) that the results obtained from single species tests cannot easily be applied to natural field conditions because the test organisms are extensively laboratory acclimated; also the test conditions provide for optimized growth and survival, a situation unlikely to be found in the field. Moreover, a fundamental problem with this approach is that it assumes that the ecosystem is a collection of single species exposed to toxicants under constant conditions (Cairns, 1982). Multi-species toxicity tests, that is the use of mixed cultures or communities of micro-organisms for a testing protocol, are found to be generally much less sensitive than single species tests (Dutka & Kwan, 1984).(ABSTRACT TRUNCATED AT 400 WORDS)

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Activated Sludge Process Response to Variable Inputs of Volatile Organic Contaminants

Cited by 10 publications

References 0 publications

Fate of volatile organic compounds in municipal activated sludge plants

Fate of volatile organic compounds in municipal activated sludge plants

Modeling of sequencing batch reactors treating inhibitory and noninhibitory wastewaters

Treatability, Toxicity and Biodegradability Test Methods

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