Minimization of excess sludge production by increase of oxygen concentration in activated sludge flocs; experimental and theoretical approach

Abbassi, Bassim; Dullstein, S; Räbiger, Norbert

doi:10.1016/s0043-1354(99)00108-6

Cited by 92 publications

(56 citation statements)

References 10 publications

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“…Shear forces introduced by aeration and sludge decay (e.g. endogenous respiration) are known to break up sludge flocs in smaller particles [61,62]. The difference between ER-30 and the other samples mostly reflects the effect of long-term aeration on particle size reduction.…”

Section: Psd and Turbiditymentioning

confidence: 99%

Physical and biochemical changes in sludge uponTubifex tubifexpredation

Valk

Khadem

Foreman

et al. 2016

Environmental Technology

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Worm predation (WP) on activated sludge leads to increased sludge degradation rates, irrespective of the type of worm used or reactor conditions employed. However, the cause of the increased sludge degradation rates remains unknown. This paper presents a comparative analysis of the physical and biochemical aspects of predated sludge, providing insight into the hydrolytic mechanisms underlying WP. To this end, the sessile worm Tubifex tubifex was used as a model oligochaete and was batch cultivated in an 18-L airlift reactor. Predation on activated sludge showed an average reduction rate of 12 ± 3.8%/d versus 2 ± 1.3%/d for endogenous respirated sludge. Sludge predation resulted in an increased release of inorganic nitrogen, phosphate and soluble chemical oxygen demand (sCOD). The sCOD consisted mainly of polysaccharides; however, fluorescence excitation emission matrix spectroscopy analysis also revealed the presence of Tryptophan-protein-like substances. Results suggest that the released polysaccharides contain a protein-like element. Additionally, soluble iron increased slightly in concentration after WP. The extent of hydrolysis seemed to reach an average plateau of about 40% volatile solids (VS) reduction after 4 days, which is substantially higher than the 29% VS reduction for endogenous decay of activated sludge after 30 days. Furthermore, T. tubifex predominantly consumed the protein fraction of the extracellular polymeric substances. Results suggest that that the worms specifically target a fraction of the sludge that is predominantly biodegradable under aerobic conditions, albeit at significantly higher degradation rates when compared to the endogenous decay of waste activated sludge. ARTICLE HISTORY

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Section: Psd and Turbiditymentioning

confidence: 99%

Physical and biochemical changes in sludge uponTubifex tubifexpredation

Valk

Khadem

Foreman

et al. 2016

Environmental Technology

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“…But the comparison and evaluation of these processes for sludge lysis is not considered in this paper. Sludge lysis and subsequently cryptic growth could be promoted by physical, chemical and combined ways in order to reduce sludge production, such as ozonation [31][32][33][34][35][36][37][38], chlorination [39,40], integration of thermal/ ultrasonic treatment and membrane [41,42], integration of alkaline and heat treatment [43][44][45], and increase of oxygen concentration [46]. Table 1 summarizes sludge reduction under lysis-cryptic growth condition.…”

Section: Lysis-cryptic Growthmentioning

confidence: 99%

“…In this system, parts of sludge from aeration tank of MBR was disintegrated with a sonicater and then supplied to the MBR as a feed solution. The MLSS in the aeration tank could be maintained at about 7.5 g/l, while that of the conventional MBR increased Increasing DO Lab scale; synthetic wastewater; increasing DO from 2 to 6 mg/l 25 - [46] from 7.0 to 13.7 g/l during 28 days. Due to a disintegration system introduced in MBR, the actual reaction parameters could be quite different from those in the conventional MBR or activated sludge processes.…”

Section: Other Lysis Techniquesmentioning

confidence: 99%

“…In this model, a new definition of F=M ratio for the MBR-SD system was suggested to evaluate its actual organic loading rate, and the actual F=M ratio was much higher than the apparent F =M ratio in the MBR-SD. Abbassi et al [46] investigated the ability for minimization of excess sludge production by mainly optimizing the oxygen concentration in the activated sludge flocs. Their results showed that a rise of the dissolved oxygen (DO) concentration from 2 to 6 mg/l led to about 25% sludge reduction at the sludge loading of 1.7 mg BOD 5 /(mg MLSS d).…”

Section: Other Lysis Techniquesmentioning

confidence: 99%

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Minimization of excess sludge production for biological wastewater treatment

Wei

Houten²,

Borger³

et al. 2003

Water Research

618

278

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Excess sludge treatment and disposal currently represents a rising challenge for wastewater treatment plants (WWTPs) due to economic, environmental and regulation factors. There is therefore considerable impetus to explore and develop strategies and technologies for reducing excess sludge production in biological wastewater treatment processes. This paper reviews current strategies for reducing sludge production based on these mechanisms: lysis-cryptic growth, uncoupling metabolism, maintenance metabolism, and predation on bacteria. The strategies for sludge reduction should be evaluated and chosen for practical application using costs analysis and assessment of environmental impact. High costs still limit technologies of sludge ozonation-cryptic growth and membrane bioreactor from spreading application in full-scale WWTPs. Bioacclimation and harmful to environment are major bottlenecks for chemical uncoupler in practical application. Sludge reduction induced by oligochaetes may present a cost-effective way for WWTPs if unstable worm growth is solved. Employing any strategy for reducing sludge production may have an impact on microbial community in biological wastewater treatment processes. This impact may influence the sludge characteristics and the quality of effluent. r

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“…Raising the concentration of dissolved oxygen in the sludge and thus stimulating the microbial activity responsible for mineralization of the sludge enhances the reduction of the excess sludge production (Abbassi et al, 1999). The number of parameters affecting the bacteria in biological wastewater treatment plants is immense and is continuously varying in time.…”

Section: Introductionmentioning

confidence: 99%

Sludge Reduction by Predatory Activity of Aquatic Oligochaetes in Wastewater Treatment Plants: Science or Fiction? A Review

Ratsak

Verkuijlen²

2006

Hydrobiologia

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Biological aerobic wastewater treatment plants (WWTPs) produce a lot of excess sludge. The costs for handling this residual product are increasing, so the search for alternative techniques to reduce the amount of sludge has to be continued. Activated sludge consists of inorganic and organic substances, bacteria, protozoa and metazoa. Due to incomplete biomass conversion, sludge consumption yields less oligochaete biomass. From a technological point of view, the application of aquatic oligochaetes to reduce the sludge production offers interesting perspectives. This paper aims to review the feasibility for the reduction of activated sludge in WWTPs by means of aquatic oligochaetes. Also the current techniques concerning sludge reduction are taken into account. Several of the WWTPs relevant parameters, which may influence predatory activity of aquatic oligochaetes, are discussed: particle size, organic content of substrate, bacteria preference, life cycle and population dynamics of aquatic oligochaetes, temperature, pH, oxygen and process conditions. From the literature it appeared that most research has been performed on laboratory scale. Only a few authors mention a significant reduction of the sludge production by 'sessile' species such as Lumbriculus. Vermicultures for the reduction of activated sludge are rather common in developing countries. Incidentally large annelid blooms have been noticed in WWTPs. It remains obscure which factors trigger the initiation of annelid blooms in WWTPs and which are of importance to maintain a stable annelid population in WWTPs. The influence of a considerable worm bloom on the waste sludge production is still under investigation.

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Minimization of excess sludge production by increase of oxygen concentration in activated sludge flocs; experimental and theoretical approach

Cited by 92 publications

References 10 publications

Physical and biochemical changes in sludge uponTubifex tubifexpredation

Physical and biochemical changes in sludge uponTubifex tubifexpredation

Minimization of excess sludge production for biological wastewater treatment

Sludge Reduction by Predatory Activity of Aquatic Oligochaetes in Wastewater Treatment Plants: Science or Fiction? A Review

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