Nitrogen removal from activated sludge process (ASP) treated municipal wastewater by biofilm channeling

Abstract Nitrous oxide emissions can contribute significantly to the carbon footprint of municipal wastewater treatment plants even though emissions from conventional nitrogen removal processes are assumed to be moderate. An increased risk for high emissions can occur in connection with process disturbances and nitrite (NO2−) accumulation. This work describes the findings at a large municipal wastewater treatment plant where the levels of NO2− in the activated sludge process effluent were spontaneously and strongly increased on several activated sludge lines which was suspected to be due to shortcut nitrogen removal that stabilized for several months. The high NO2− levels were linked to a dramatic increase in nitrous oxide (N2O) emissions. As much as over 20% of the daily influent nitrogen load was emitted as N2O. These observations indicate that highly increased NO2− levels can occur in conventional activated sludge processes and result in high nitrous oxide emissions. They also raise questions concerning the risk of increased greenhouse gas (GHG) emissions of the nitritation-denitritation processes – although the uncontrolled nature of the event described here must be taken into consideration – and underline the importance of continuous monitoring and control of N2O emissions.

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Biological nutrient removal at a very low-loaded activated sludge plant with high biomass concentrations

Water Science & Technology ◽

10.2166/wst.1998.0017 ◽

1998 ◽

Vol 38 (1) ◽

pp. 63-70 ◽

Cited By ~ 1

Author(s):

H. J. Kiuru ◽

J. A. Rautiainen

Keyword(s):

Activated Sludge ◽

Total Nitrogen ◽

Total Phosphorus ◽

Nitrogen Removal ◽

Nutrient Removal ◽

Municipal Wastewater ◽

Treated Wastewater ◽

Biological Nutrient Removal ◽

Activated Sludge Process ◽

Biological Phosphorus

The Laboratory of Environmental Engineering at the Helsinki University of Technology (HUT) carried out in 1991-1995 two successive full-scale research and development projects at the Pihlajaniemi WWTP of Savonlinna concerning biological nutrient removal from municipal wastewater. The projects have resulted in two reports in Finnish with quite large English summaries. This WWTP was constructed originally (1978) as a conventional low-loaded activated sludge plant with the simultaneous precipitation of phosphorus. It was dimensioned for a sludge concentration of 3.5 kgMLSS/m3 in the aeration tanks. Six years later (1984) the plant was fitted with a tertiary stage of flotation filters in order to improve the removal of suspended solids and phosphorus. Nitrification was introduced to the activated sludge process of the plant in 1987. It could be done without any extension by using the sludge concentrations of 6-10 kgMLSS/m3 in the aeration tanks. In that way, this activated sludge process was converted into a very low-loaded one. The process became able to nitrify totally in the circumstances in which the wastewater temperature varies at the range of 4-20°C. The actual hydraulic as well as the BOD7-load of the plant are about 40% of the original dimensioned ones. This activated sludge process of the Pihlajaniemi WWTP was modified in 1991-1993 for nitrogen removal and then in 1994-1995 for both biological phosphorus and nitrogen removal Denitrification was introduced to the process and the simultaneous precipitation of phosphorus in that was replaced by biological phosphorus removal still without any extension of the activated sludge process. The plant has now been operated over four years with biological nutrient removal exploiting the organic carbon compounds of the wastewater. A very little addition of some precipitant is used to improve the biological removal of phosphorus. The chemical and energy cost of the plant has been reduced by some 50% due to the introduction of biological nutrient removal. The BOD7-value of the treated wastewater is mainly less than 3 mg/l (always less than 5 mg/l). The content of total phosphorus in the treated wastewater is usually less than 0.3 mg/l (always less than 0.5 mg/l). The content of total nitrogen in the treated wastewater is mainly 8-12 mg/l. Reductions for BOD7 and total phosphorus over 95% as well as that for total nitrogen about 70% are achieved.

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ENHANCED NITROGEN REMOVAL FROM REJECT WATER OF MUNICIPAL WASTEWATER TREATMENT PLANTS USING A NOVEL EXCESS ACTIVATED SLUDGE (EAS) BASED NITRIFICATION AND DENITRIFICATION PROCESS

Environmental Engineering and Management Journal ◽

10.30638/eemj.2013.168 ◽

2013 ◽

Vol 12 (7) ◽

pp. 1367-1373

Author(s):

Yongzhe Yang ◽

Xiaoxia Yang ◽

Wei Li ◽

Xinchao Guo

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Nitrogen Removal ◽

Municipal Wastewater ◽

Wastewater Treatment Plants ◽

Municipal Wastewater Treatment ◽

Reject Water ◽

Nitrification And Denitrification ◽

Municipal Wastewater Treatment Plants ◽

Denitrification Process

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Operational Results of the Wolfsburg Wastewater Treatment Plant

Water Science & Technology ◽

10.2166/wst.1992.0496 ◽

1992 ◽

Vol 25 (4-5) ◽

pp. 203-209 ◽

Cited By ~ 7

Author(s):

R. Kayser ◽

G. Stobbe ◽

M. Werner

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Nitrogen Content ◽

Total Nitrogen ◽

Nitrogen Removal ◽

Wastewater Treatment Plant ◽

Treatment Plant ◽

Phosphate Removal ◽

Total Nitrogen Content ◽

Activated Sludge Process

At Wolfsburg for a load of 100,000 p.e., the step-feed activated sludge process for nitrogen removal is successfully in operation. Due to the high denitrification potential (BOD:TKN = 5:1) the effluent total nitrogen content can be kept below 10 mg l−1 N; furthermore by some enhanced biological phosphate removal about 80% phosphorus may be removed without any chemicals.

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Specific organic and nutrient loads in stabilized sludge from municipal treatment plants

Water Science & Technology ◽

10.2166/wst.1996.0342 ◽

1996 ◽

Vol 33 (12) ◽

pp. 243-250 ◽

Cited By ~ 1

Author(s):

O. Nowak ◽

A. Franz ◽

K. Svardal ◽

V. Müller

Keyword(s):

Activated Sludge ◽

Nitrogen Removal ◽

Single Stage ◽

Nutrient Loads ◽

Activated Sludge Process ◽

Waste Sludge ◽

Sludge Stabilization ◽

Nitrogen Loads ◽

Theoretical Considerations ◽

P Removal

By means of theoretical considerations and of statistical evaluations, specific organic and nitrogen loads in separately stabilized sludge have been found to be in the range of 16 to 20g VSS/PE/d and of 1.1 to 1.5 g N/PE/d respectively. About 0.6g P/PE/d are removed from the wastewater in activated sludge plants without chemical or enhanced biological P removal. By using the single-stage activated sludge process without primary sedimentation and without separate sludge stabilization, almost complete nitrogen removal can be achieved, but specific organic and nitrogen loads in the waste sludge are up to two times higher than in separately stabilized sludge.

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Cultivation of rice for animal feed with circulated irrigation of treated municipal wastewater for enhanced nitrogen removal: comparison of cultivation systems feeding irrigation water upward and downward

Water Science & Technology ◽

10.2166/wst.2015.251 ◽

2015 ◽

Vol 72 (4) ◽

pp. 579-584 ◽

Cited By ~ 7

Author(s):

A. Muramatsu ◽

H. Ito ◽

A. Sasaki ◽

A. Kajihara ◽

T. Watanabe

Keyword(s):

Nitrogen Removal ◽

Irrigation Water ◽

Rice Plant ◽

Municipal Wastewater ◽

Animal Feed ◽

Paddy Fields ◽

Treated Wastewater ◽

Human Consumption ◽

Cultivation System ◽

Treated Municipal Wastewater

To achieve enhanced nitrogen removal, we modified a cultivation system with circulated irrigation of treated municipal wastewater by using rice for animal feed instead of human consumption. The performance of this modified system was evaluated through a bench-scale experiment by comparing the direction of circulated irrigation (i.e. passing through paddy soil upward and downward). The modified system achieved more than three times higher nitrogen removal (3.2 g) than the system in which rice for human consumption was cultivated. The removal efficiency was higher than 99.5%, regardless of the direction of circulated irrigation. Nitrogen in the treated municipal wastewater was adsorbed by the rice plant in this cultivation system as effectively as chemical fertilizer used in normal paddy fields. Circulated irrigation increased the nitrogen released to the atmosphere, probably due to enhanced denitrification. Neither the circulation of irrigation water nor its direction affected the growth of the rice plant and the yield and quality of harvested rice. The yield of rice harvested in this system did not reach the target value in normal paddy fields. To increase this yield, a larger amount of treated wastewater should be applied to the system, considering the significant amount of nitrogen released to the atmosphere.

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

Water Science & Technology ◽

10.2166/wst.2018.334 ◽

2018 ◽

Vol 78 (3) ◽

pp. 644-654 ◽

Cited By ~ 3

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.

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