Experimental study on sludge reduction by ultrasound

2006 ◽  
Vol 54 (9) ◽  
pp. 87-93 ◽  
Author(s):  
X.Q. Cao ◽  
J. Chen ◽  
Y.L. Cao ◽  
J.Y. Zhu ◽  
X.D. Hao
Keyword(s):  
Treatment Time ◽  
Cost Effective ◽  
Ultrasound Treatment ◽  
Sludge Reduction ◽  
Sonication Time ◽  
Excess Sludge ◽  
Effluent Quality ◽  
Ultrasonic Intensity ◽  
Sludge Settleability ◽  
Sludge Production

In recent years, considerable impetus emerges to develop strategies for reducing excess sludge produced in biological wastewater treatment (BWT) systems. In this study, an experiment on sludge reduction by ultrasound treatment was conducted. The influences of sonication on observed yield, sludge reduction, effluent quality, sludge settleability and stability were extensively evaluated. It was found that ultrasound had an impressive potential to reduce sludge production. Moreover, it was also concluded that a treatment time of 10 minutes was more cost-effective for sludge reduction, and a reduction by 44% was reached with an ultrasonic intensity of 0.25 w/ml. The reduction could be mainly attributed to disintegration of bio-flocs and cryptic growth. In addition, sonication time seemed to be more effective to reduce sludge production compared with ultrasonic intensity. Slight deterioration of the effluent quality and some variations of the sludge settleability and stability were observed after ultrasound treatment.

New approaches to minimize excess sludge in activated sludge systems

2001 ◽  
Vol 44 (10) ◽  
pp. 203-208 ◽  
Author(s):  
G.-H. Chen ◽  
S. Saby ◽  
M. Djafer ◽  
H.-K. Mo
Keyword(s):  
Activated Sludge ◽  
Activated Sludge Process ◽  
Conventional System ◽  
Excess Sludge ◽  
Active Sludge ◽  
New Approaches ◽  
Conventional Activated Sludge ◽  
Sludge Settleability ◽  
Activated Sludge Systems ◽  
Sludge Production

This paper presents three new approaches to reduce excess sludge production in activated sludge systems: 1) modification of conventional activated sludge process with insertion of a sludge holding tank in the sludge return line; 2) chlorination of excess sludge so as to minimize excess sludge production; and 3) utilization of a metabolic uncoupler, 3, 3′, 4′, 5-Tetrachlorosalicylanilide (TCS) to maximize futile activity of sludge microorganisms thereby leading to a reduction of sludge growth. Pilot study was carried out to evaluate this modified activated sludge process (OSA). It has been confirmed that the OSA process is effective in reducing excess sludge; particularly when the ORP level in the sludge holding tank was kept at -250 mV, more than 50% of the excess sludge was reduced. This process can maintain the effluent quality and even perform with a better sludge settleability than a conventional system. Experimental work on the second approach showed that chlorination treatment of excess sludge at a chlorine dose of 0.066 g Cl2/g MLSS reduced the excess sludge by 60%, while concentration of THMS was found below 200 ppb in the treated sludge. However, such sludge chlorination treatment sacrificed sludge settleability. Thus, it is not feasible to introduce the chlorination step to a conventional system. The third approach confirmed that addition of TCS could reduce sludge growth effectively if the TCS concentration is greater than 0.4 ppm. A 0.8-ppm concentration of TCS actually reduced excess sludge by 45%. It was also experimentally demonstrated that presence of TCS increases the portion of active sludge microorganisms over the entire microbial population.

Enhanced reduction of excess sludge and nutrient removal in a pilot-scale A2O-MBR-TAD system

2011 ◽  
Vol 63 (8) ◽  
pp. 1547-1556 ◽  
Author(s):  
J. S. Ventura ◽  
S. Seo ◽  
I. Chung ◽  
I. Yeom ◽  
H. Kim ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Nutrient Removal ◽  
Domestic Wastewater ◽  
Pilot Scale ◽  
Excess Sludge ◽  
E Coli ◽  
Effluent Quality ◽  
Cryptic Growth ◽  
A2o Process ◽  
Sludge Production

In this study, a pilot scale anaerobic-anoxic-oxic (A2O) process with submerged membrane (MBR) in the oxic tank was coupled with thermophilic aerobic digestion (TAD) reactor and was operated for longer than 600 days to treat real domestic wastewater. Regardless of the varying conditions of the system, the A2O-MBR-TAD process removed MLSS, TCOD, BOD, TN, TP, and E. coli about 99%, 96%, 96%, 70%, 83%, and 99%, respectively. The additional TP removal of the system was due to the precipitating agent directly added in the oxic reactor, without which TP removal was about 56%. In the TAD reactor, receiving MLSS from the oxic tank (MBR), about 25% of TSS and VSS were solubilized during 2 days of retention. The effluent of the TAD reactor was recycled into the anoxic tank of A2O-MBR to provide organic carbon for denitrification and cryptic growth. By controlling the flowrate of wasting stream from the MBR, sludge production decreased to almost zero. From these results, it was concluded that the A2O-MBR-TAD process could be a reliable option for excellent effluent quality and near zero-sludge production.

Improvement and prediction of OSA system performance in sludge reduction through integration with thermal and mechanical treatment

2016 ◽  
Vol 74 (9) ◽  
pp. 2087-2096 ◽  
Author(s):  
Sara Nazif ◽  
Naser Mehrdadi ◽  
Sajad Zare ◽  
Sarvenaz Mosavari
Keyword(s):  
Thermal Treatment ◽  
Mechanical Treatment ◽  
Removal Rate ◽  
Batch Reactor ◽  
Cod Removal ◽  
Aeration Tank ◽  
Sludge Reduction ◽  
Mechanical Mixing ◽  
Effluent Quality ◽  
Sludge Production

The oxic–settling–anoxic (OSA) process is one of the sludge production reduction methods in the activated sludge process. In this method, sludge is stored in an anaerobic tank within the sludge return line before entrance into an aeration tank. Due to this method's flexibility in application to operating treatment plants and not being energy-consuming, its application is developing. In this research, the improvement of the OSA process is investigated via thermal and mechanical treatment in a sequencing batch reactor (SBR). A pilot-scale reactor and domestic wastewater are used. Sludge was subjected to high temperature in an anaerobic tank using a heat transformer and it was subjected to mechanical shear through mechanical mixing in the anaerobic tank. Different temperatures and voltages were tested. The OSA process reduced sludge production by 24% while the chemical oxygen demand (COD) removal rate decreased from 90% to 86%. Thermal treatment combined with the OSA process caused a maximum of 46% sludge production reduction. However temperatures above 90 °C are not recommended due to a high level of decrease in COD removal. Mechanical mixing in combination with the OSA process led to 34% sludge production reduction. The effluent quality is not affected by the OSA process itself but is slightly reduced by thermal treatment and mechanical mixing. Therefore, for reaching the maximum sludge reduction in OSA plus thermal and mechanical treatment it would be necessary to evaluate the effect of different sets of parameters on effluent quality beside the sludge reduction. For this purpose multi-layer perceptron artificial neural network models are developed to predict the effluent total suspended solids and COD removal efficiency as well as sludge production rate. The models perform well and would be useful tools in determining the optimal set of system operation parameters.

Transformation and Migration of Heavy Metals by Aquatic Worms in Wastewater Treatment

2012 ◽  
Vol 573-574 ◽  
pp. 526-533
Author(s):  
Wei Fei Huang ◽  
Ying Gang Shu ◽  
Lu Cai ◽  
Sheng Liang Si
Keyword(s):  
Heavy Metals ◽  
Wastewater Treatment ◽  
Activated Sludge ◽  
Environmental Risk ◽  
Sludge Reduction ◽  
Excess Sludge ◽  
Safe Disposal ◽  
Waste Sludge ◽  
And Migration ◽  
Sludge Settleability

L. hoffmeisteri was inoculated in reactor to investigate the effects on waste sludge and wastewater to reduce excess sludge and reduce the environmental risk of heavy metals in sludge and effluent in this study. The result showed a gravimetric sludge reduction of 53.8% and modification in the texture of the sludge. The residual form of heavy metals (As, Cd, Cr, Cu, Ni, Pb and Zn) was increased, which reduced the risk of the phytoaccumulation. An evident concentration of heavy metals in worm faece and a bioaccumulation of heavy metals in aquatic worms were also observed. Activated sludge is reduced significantly, sludge settleability is improved and the bioavailability of heavy metals in waste sludge is minimized, which are beneficial to wastewater treatment and safe disposal of waste sludge.

Two-stage chemical-biological treatment at Thessaloniki greater area WWTP - experiences and potentials

1995 ◽  
Vol 32 (9-10) ◽  
pp. 75-84 ◽  
Author(s):  
A. D. Andreadakis ◽  
G. H. Kristensen ◽  
A. Papadopoulos ◽  
C. Oikonomopoulos
Keyword(s):  
Biological Treatment ◽  
Treatment Plant ◽  
Cost Effective ◽  
Primary Treatment ◽  
Effective Control ◽  
Two Stage ◽  
Effluent Quality ◽  
Filamentous Microorganisms ◽  
Sludge Settling ◽  
The City

The wastewater from the city of Thessaloniki is discharged without treatment to the nearby inner part of the Thessaloniki Gulf. The existing, since 1989, treatment plant offers only primary treatment and did not operate since the expected effluent quality is not suitable for safe disposal to the available recipients. Upgrading of the plant for advanced biological treatment, including seasonal nitrogen removal, is due from 1995. In the mean time, after minor modifications completed in February 1992, the existing plant was put into operation as a two-stage chemical-biological treatment plant for 40 000 m3 d−1, which corresponds to about 35% of the total sewage flow. The operational results obtained during the two years operation period are presented and evaluated. All sewage and sludge treatment units of the plant perform better than expected, with the exception of the poor sludge settling characteristics, due to severe and persistent bulking caused by excessive growth of filamentous microorganisms, particularly M. Parvicella. Effective control of the bulking problem could lead to more cost-effective operation and increased influent flows.

Monitoring effluent quality in hypertrophic wastewater reservoirs using remote sensing

1996 ◽  
Vol 33 (8) ◽  
pp. 23-29 ◽  
Author(s):  
I. Dor ◽  
N. Ben-Yosef
Keyword(s):  
Water Quality ◽  
Theoretical Model ◽  
Principal Component ◽  
Cost Effective ◽  
Operational Parameters ◽  
Effluent Quality ◽  
Optical Images ◽  
Routine Monitoring ◽  
Cost Effective Method ◽  
Wastewater Quality

About one hundred and fifty wastewater reservoirs store effluents for irrigation in Israel. Effluent qualities differ according to the inflowing wastewater quality, the degree of pretreatment and the operational parameters. Certain aspects of water quality like concentration of organic matter, suspended solids and chlorophyll are significantly correlated with the water column transparency and colour. Accordingly optical images of the reservoirs obtained from the SPOT satellite demonstrate pronounced differences correlated with the water quality. The analysis of satellite multispectral images is based on a theoretical model. The model calculates, using the radiation transfer equation, the volume reflectance of the water body. Satellite images of 99 reservoirs were analyzed in the chromacity space in order to classify them according to water quality. Principal Component Analysis backed by the theoretical model increases the method sensitivity. Further elaboration of this approach will lead to the establishment of a time and cost effective method for the routine monitoring of these hypertrophic wastewater reservoirs.

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