Nocardia effects in waste activated sludge

1998 ◽  
Vol 38 (2) ◽  
pp. 49-54 ◽  
Author(s):  
Krishna R. Pagilla ◽  
David Jenkins ◽  
Wendell Kido
Keyword(s):  
Activated Sludge ◽  
Foam Stability ◽  
Anaerobic Digester ◽  
Waste Activated Sludge ◽  
Dissolved Air Flotation ◽  
Anaerobic Digesters ◽  
Primary Sludge ◽  
Mixed Liquor ◽  
Dissolved Air ◽  
Batch Foaming

Two effects of Nocardia in waste activated sludge (WAS) were investigated: (i) the influence of WAS in the solids treatment recycle streams on Nocardia persistence in the activated sludge, and (ii) the effect of Nocardia in WAS on anaerobic digester foaming. About 4% of the Nocardia present in the mixed liquor was due to seeding from the WAS solids in the dissolved air flotation thickener recycle stream recycle. Nocardia filaments in WAS at levels of between 104 to 106 intersections/g VSS resulted in Nocardia levels of approximately 104 to 105 intersections/g VSS in anaerobic digesters that treated both WAS and primary sludge. The effect of disinfecting these Nocardia filaments in the WAS with Cl2 was investigated at Cl2 dose ranges of 20-60 mg Cl2/l WAS and 100-200 mg Cl2/l WAS on a lab scale using batch foaming tests to assess success. Chlorination with 20 - 60 mg Cl2/l WAS approximately doubled both sludge foaming potential and foam stability. At Cl2 doses of 100-200 mg Cl2/l WAS, foaming potential was increased almost 10-fold, and foam stability was increased by 2.5 times. These results indicate that chlorination of WAS feed to an anaerobic digester for inactivation of Nocardia should not be practiced.

Effect of primary sludge to waste activated sludge mixing ratio on anaerobic digester performance

2017 ◽  
Vol 71 ◽  
pp. 79-84
Author(s):  
Anteneh Mesfin Yeneneh ◽  
Tushar Kanti Sen ◽  
Ahmet Kayaalp ◽  
Ha Ming Ang
Keyword(s):  
Activated Sludge ◽  
Anaerobic Digester ◽  
Waste Activated Sludge ◽  
Mixing Ratio ◽  
Primary Sludge

Causes and effects of foaming in anaerobic sludge digesters

1997 ◽  
Vol 36 (6-7) ◽  
pp. 463-470 ◽  
Author(s):  
Krishna R. Pagilla ◽  
Kent C. Craney ◽  
Wendell H. Kido
Keyword(s):  
Activated Sludge ◽  
Full Scale ◽  
Anaerobic Sludge ◽  
Waste Activated Sludge ◽  
Foam Layer ◽  
Anaerobic Digesters ◽  
Primary Sludge ◽  
Total Solids ◽  
Volatile Solids ◽  
Different Depths

Full scale anaerobic digesters treating mixed sludge containing primary sludge and thickened waste activated sludge were investigated for causes and effects of foaming. Sludge samples were collected from different depths of two full scale digesters, one gas-mixed, and the other mechanically-mixed, to determine the extent of foaming and its effects on anaerobic digestion; both digesters were fed the same feed sludge (3.4% TS) and at the same feed rate (about 2.2 kg TS/m3.day). The average depth of the surface foam layer in the gas-mixed and mechanically-mixed digester were 2.4 and 1.3 m respectively. Higher total solids concentrations were found at the surface (about 5% TS) than those found at the bottom (about 2% TS) in both gas-mixed and mechanically-mixed digesters, indicating an inverse total solids profile. Presence of excessive levels of Nocardia filaments (>106 number/g VSS) in the activated sludge caused thicker foam layer at the surface, and this effect was more pronounced in the gas-mixed digester than in the mechanically-mixed digester. Gas-mixed digester (0.74 m3/kg VS destroyed) produced less sludge gas than the mechanically-mixed digester (0.93 m3/kg VS destroyed), however, gas-mixed digester (62% VS reduction) destroyed more volatile solids than the mechanically-mixed digester (54% VS reduction). These results indicate that gas-mixed digesters are more prone to foaming than mechanically-mixed digesters, and that the foaming can increase when excessive levels of Nocardia filaments are present in the feed sludge causing decreased digester performance.

scholarly journals Microalgae as biological treatment for municipal wastewater – effects on the sludge handling in a treatment plant

2018 ◽  
Vol 78 (3) ◽  
pp. 644-654 ◽  
Author(s):  
J. Olsson ◽  
S. Schwede ◽  
E. Nehrenheim ◽  
E. Thorin
Keyword(s):  
Heavy Metals ◽  
Activated Sludge ◽  
Biological Treatment ◽  
Municipal Wastewater ◽  
Treatment Plant ◽  
Waste Activated Sludge ◽  
Activated Sludge Process ◽  
Primary Sludge ◽  
Thermophilic Conditions ◽  
Mesophilic Conditions

Abstract A mix of microalgae and bacteria was cultivated on pre-sedimented municipal wastewater in a continuous operated microalgae-activated sludge process. The excess material from the process was co-digested with primary sludge in mesophilic and thermophilic conditions in semi-continuous mode (5 L digesters). Two reference digesters (5 L digesters) fed with waste-activated sludge (WAS) and primary sludge were operated in parallel. The methane yield was slightly reduced (≈10%) when the microalgal-bacterial substrate was used in place of the WAS in thermophilic conditions, but remained approximately similar in mesophilic conditions. The uptake of heavy metals was higher with the microalgal-bacterial substrate in comparison to the WAS, which resulted in higher levels of heavy metals in the digestates. The addition of microalgal-bacterial substrate enhanced the dewaterability in thermophilic conditions. Finally, excess heat can be recovered in both mesophilic and thermophilic conditions.

Flotation efficiency of activated sludge flocs using population balance model in dissolved air flotation

2006 ◽  
Vol 23 (2) ◽  
pp. 271-278 ◽  
Author(s):  
Heung-Joe Jung ◽  
Jae-Wook Lee ◽  
Do-Young Choi ◽  
Seong-Jin Kim ◽  
Dong-Heui Kwak
Keyword(s):  
Activated Sludge ◽  
Population Balance ◽  
Balance Model ◽  
Population Balance Model ◽  
Dissolved Air Flotation ◽  
Sludge Flocs ◽  
Air Flotation ◽  
Dissolved Air

Thermochemical pretreatment in the anaerobic digestion of waste activated sludge

2002 ◽  
Vol 46 (10) ◽  
pp. 173-179 ◽  
Author(s):  
S. Tanaka ◽  
K. Kamiyama
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Municipal Sewage ◽  
Waste Activated Sludge ◽  
Anaerobic Digesters ◽  
Thermochemical Pretreatment ◽  
Methane Production Rate

Effects of a thermochemical pretreatment on the anaerobic digestion of waste activated sludge (WAS) was investigated by semicontinuously-fed digesters operated at 37¡C. WAS from a return sludge line of a municipal sewage treatment plant was pretreated by autoclaving at 130°C for 5 minutes after adding 0.3g NaOH/g VSS. Solids of WAS were thermochemically solubilized to one half and then 60% or more were in totality solubilized in anaerobic digesters fed with pretreated WAS at 2-8 days of hydraulic retention times (HRT), while only 16-36% were solubilized in digesters fed with raw WAS. The adverse effect of the set temperature (130°C) on the biodegradability of protein was not found. As a result, removal rates of COD in digestion was increased from 38% to 57% at 8 days HRT by the pretreatment. A specific methane production rate in the pretreated process was three times as high as the normal process. The thermochemical pretreatment was found to be very effective to enhance biodegradability as well as solubilization of WAS in anaerobic digestion.

Low temperature microwave and conventional heating pre-treatments to improve sludge anaerobic biodegradability

2013 ◽  
Vol 69 (3) ◽  
pp. 518-524 ◽  
Author(s):  
P. Vergine ◽  
J. Zábranská ◽  
R. Canziani
Keyword(s):  
Low Temperature ◽  
Activated Sludge ◽  
Oxygen Demand ◽  
Cost Effective ◽  
Conventional Heating ◽  
Waste Activated Sludge ◽  
Experimental Conditions ◽  
Primary Sludge ◽  
Batch Tests ◽  
Pre Treatment

This paper presents the results of lab-scale experiments on low temperature thermal pre-treatment (less than 100 °C) prior to anaerobic digestion of sewage sludge. Two heating ways, microwave heating (MH) and conventional heating (CH), and two types of sludge, primary and waste activated sludge, were compared under the same experimental conditions. The degree of solubilisation produced by MH and CH up to 72, 82 and 93 °C was firstly estimated. For both types of heating, increase in soluble chemical oxygen demand (COD) caused by the pre-treatment was about 14% on waste activated sludge and only 3% on primary sludge. The final temperature of 72 °C resulted as the most cost-effective in terms of additional soluble COD per unit of energy required. Subsequently, five series of biochemical methane potential mesophilic assays were run in 120 mL serum bottles on sludge samples pre-treated at 72 °C. When compared with control reaction vessels, no significant differences were noticed in net methane production of pre-treated primary sludge, whereas a relevant increase occurred regarding the pre-treated waste activated sludge. It was also observed that the trend of methane content in biogas during the batch tests can be described by a second order polynomial.

Sign in / Sign up

Export Citation Format

Share Document