Organic matter release in low temperature thermal treatment of biological sludge for reduction of excess sludge production

2006 ◽  
Vol 54 (5) ◽  
pp. 59-68 ◽  
Author(s):  
E. Paul ◽  
P. Camacho ◽  
D. Lefebvre ◽  
P. Ginestet
Keyword(s):  
Heat Treatment ◽  
Organic Matter ◽  
Thermal Treatment ◽  
Activated Sludge ◽  
Order Kinetic ◽  
Excess Sludge ◽  
Digested Sludge ◽  
Significant Difference ◽  
The Impact ◽  
Sludge Production

Thermal treatment applied in association with a biological system allows for a significant reduction in excess sludge production (∼50%). In general, heat treatment is described as a sludge disintegration technique. This paper offers a thorough study on the impact of heat treatment, at temperatures below 100 °C, on the solubilisation of the sludge COD and its biodegradability. Discontinuous heating experiments were performed on activated and digested sludge. At all temperatures tested the released COD for digested sludge was systematically higher than that for activated sludge (15 and 40%, respectively, at 95 °C for 40 min of contact time). For the first 30 min, a 1st order kinetic, with respect to the residual COD, was systematically found. In the range of 40–95 °C, digested sludge had a lower activation energy than activated sludge (26 kcal/mol compared to 70–160 kcal/mol). COD solubilisation is thus more positively influenced by temperature in the case of activated sludge. This may be due to the significant difference in the ratio of protein/carbohydrate in digested and activated sludge (1–5 and 0.2–0.7, respectively). The increase in the COD/TKN ratio in the solubilised fraction after thermal treatment of activated sludge suggests a preferential solubilisation of proteins over carbohydrates. Respirometric tests performed on the solubilised COD showed that whatever the sludge origin, only 40–50% of released COD is biodegradable at a conventional hydraulic retention time (i.e. 24 h). Hence, heat treatment would act more through organic matter solubilisation rather than by a biodegradability increase.

Mesophilic and Thermophilic Digestion of Thickened Waste Activated Sludge: A Comparative Study

2010 ◽  
Vol 113-116 ◽  
pp. 450-458 ◽  
Author(s):  
Yong Zhi Chi ◽  
Yu You Li ◽  
Min Ji ◽  
Hong Qiang ◽  
Heng Wei Deng ◽  
...  
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Treatment Plant ◽  
Methane Content ◽  
Waste Activated Sludge ◽  
Digested Sludge ◽  
Anaerobic Digestion Process ◽  
Digestion Process ◽  
Significant Difference

This paper presents an experimental study over 204 days on anaerobic degradation of thickened waste activated sludge (TWAS) from a municipal wastewater treatment plant (WWTP). The experiments were conducted under thermophilic (55°C) and mesophilic (35°C) condition, respectively, by using the semi-continuous flow completely mixed reactors. The influent total solids (TS), hydraulic retention time (HRT) and chemical oxygen demand (COD) loading levels were around 4%, 30 days and 1.67 kg-CODCr•m-3•d-1 , respectively. During the opration period, the thermophilic anaerobic digestion process (TADP) and the mesophilic anaerobic digestion process (MADP) were stable and well-functioned without ammonia inhibition. Particulate organic matters reduction of TADP was superior to that of MADP. This result implies that TADP has higher sludge reduction efficiency than MADP. According to the simulated chemical formula of TWAS, C5.85H9.75O3.96N, and the stoichiometric equation, the methane content and the ammonia yield in the anaerobic process could be calculated, which were consistent with the experimental results. The methane yield of TADP was a little higher than that of MADP. The statistical mean values of methane content for TADP and MADP were 60.97% and 62.38%, respectively.According to paired t-test, there was a significant difference in methane content between TADP and MADP(α=0.01, n=62). Compared with the mesophilic digested sludge, the dewaterability of thermophilic digested sludge was lower.

Decreased sludge production strategy for domestic wastewater treatment

1994 ◽  
Vol 30 (8) ◽  
pp. 97-106 ◽  
Author(s):  
Angel Canales ◽  
Alain Pareilleux ◽  
Jean Luc Rols ◽  
Ge´rard Goma ◽  
Alain Huyard
Keyword(s):  
Wastewater Treatment ◽  
Thermal Treatment ◽  
Cell Lysis ◽  
Production Yield ◽  
Biomass Growth ◽  
Excess Sludge ◽  
Cell Content ◽  
Content Ratio ◽  
Cryptic Growth ◽  
Sludge Production

With new EEC regulations, alternative treatment and disposal techniques of the excess sludge produced by Activated Sludge (AS) wastewater treatment plants have to be performed. In order to reduce the excess sludge produced, experiments have been carried out with a Membrane BioReactor (MBR) to study the maintenance and cryptic growth phenomena of Pseudomonas fluorescens culture taken as a model when grown on a limiting substrate complex medium similar to a synthetic urban wastewater. Experiments with various imposed wasting rates showed that viability and sludge production yield decreased when sludge age increased. Same variations were observed on the cell content ratio protein/polysaccharide by analysis of the cell lysis products released after discontinuous thermal treatment. Biomass growth on these cell lysis products was achieved to characterize cryptic growth and its impact on sludge production yield. Finally, a continuous sludge thermal treatment system was operating with MBR to amplify sludge breakage and consequently biomass growth on the lysis products. With the promising results obtained, this work gives a new outlook on the AS process and leads to the development of processes with control and reduction of sludge production.

Partial ozonation of activated sludge to reduce excess sludge, improve denitrification and control scumming and bulking

2004 ◽  
Vol 49 (10) ◽  
pp. 41-49 ◽  
Author(s):  
M. Böhler ◽  
H. Siegrist
Keyword(s):  
Activated Sludge ◽  
Cost Evaluation ◽  
Anoxic Zone ◽  
Excess Sludge ◽  
Solid Retention Time ◽  
Operation Stability ◽  
Agricultural Use ◽  
Sludge Ash ◽  
And Control ◽  
Sludge Production

Disposal of sewage sludge is forbidden and agricultural use of stabilized sludge will be banned in 2005 in Switzerland. The sludge has to be dewatered, dried, incinerated and the ashes disposed in landfills. These processes are cost intensive and lead also to the loss of valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Partial ozonation of the return sludge of an activated sludge system reduces significantly excess sludge production, improves settling properties of the sludge and reduces bulking and scumming. The solubilized COD will also improve denitrification if the treated sludge is recycled to the anoxic zone. But ozonation will partly inhibit and kill nitrifiers and might therefore lead to a decrease of the effective solid retention time of the nitrifier, which reduces the safety of the nitrification. This paper discusses the effect of ozonation on sludge reduction, the operation stability of nitrification, improvement of denitrification and gives also an energy and cost evaluation.

Classification of algogenic organic matter concerning its contribution to the bacterial regrowth potential and by-products formation

1998 ◽  
Vol 37 (2) ◽  
pp. 91-96 ◽  
Author(s):  
Wido Schmidt ◽  
Beate Hambsch ◽  
Heike Petzoldt
Keyword(s):  
Organic Matter ◽  
Chlorine Dioxide ◽  
Relative Increase ◽  
Residual Chlorine ◽  
Additional Increase ◽  
Bacterial Regrowth ◽  
Humic Compounds ◽  
Significant Difference ◽  
The Impact ◽  
By Products

The bacterial regrowth potential (BRP) and the by-products formation potential after the disinfection (DBP) are parameters recognized to be influenced by the origin of organic matter dissolved in water. A significant difference of the impact of humic compounds and algogenic organic matter (AOM), characteristic for raw waters from reservoirs, to both parameters can be assumed. In systematic laboratory experiments the influence of AOM on the BRP as well as DBP was examined. Different fractions of the AOM were chlorinated and treated with chlorine dioxide. In addition to that the influence of the ozonation was investigated. To assess the biodegradable fraction of the organic matter (BDOC) a large spectrum of by-products (aldehydes and keto-acids) was analyzed. The BRP in the water was determined by the measurement of the increase of biomass in the water samples. It could be proved, that the chlorination of intact algae cells containing waters may cause a significant increase of the biodegradability in the water if the residual chlorine is totally required. In the case of the disinfection of the AOM containing waters with chlorine dioxide the relative increase of the BRP was lower in comparison to the chlorinated waters. The preozonation of the algae containing waters indicates an additional increase of the BRP, but only by ozonation of the algae cells. The ozonation of the algae metabolites does not influence the BRP, but it causes a significant decrease of the THM-formation if chlorine is used for disinfection.

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.

scholarly journals Optimization of Ozonation Process for the Reduction of Excess Sludge Production from Activated Sludge Process of Sago Industry Wastewater Using Central Composite Design

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
B. Subha ◽  
M. Muthukumar
Keyword(s):  
Activated Sludge ◽  
Central Composite Design ◽  
Retention Time ◽  
Acidic Ph ◽  
Activated Sludge Process ◽  
Excess Sludge ◽  
Cod Reduction ◽  
Ozonation Time ◽  
Central Composite ◽  
Sludge Production

Sago industries effluent containing large amounts of organic content produced excess sludge which is a serious problem in wastewater treatment. In this study ozonation has been employed for the reduction of excess sludge production in activated sludge process. Central composite design is used to study the effect of ozone treatment for the reduction of excess sludge production in sago effluent and to optimise the variables such as pH, ozonation time, and retention time. ANOVA showed that the coefficient determination value (R2) of VSS and COD reduction were 0.9689 and 0.8838, respectively. VSS reduction (81%) was achieved at acidic pH 6.9, 12 minutes ozonation, and retention time of 10 days. COD reduction (87%) was achieved at acidic pH 6.7, 8 minutes of ozonation time, and retention time of 6 days. Low ozonation time and high retention time influence maximum sludge reduction, whereas low ozonation time with low retention time was effective for COD reduction.

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