Optimisation of biological nitrogen removal processes to treat reject water from anaerobic digestion of sewage sludge

Author

Galí Serra, Alexandre

Director

Mata Álvarez, Joan

Date of defense

2006-10-03

ISBN

8469021311

Legal Deposit

B.49997-2006



Department/Institute

Universitat de Barcelona. Departament d'Enginyeria Química i Metal·lúrgia

Abstract

In the present work, the biological treatment of real reject water (800 mg NH4+-N L-1) from anaerobic digestion of sewage sludge from a waste water treatment plant (WWTP) is carried out. <br/>The process was optimised with a Sequencing Batch Reactors (SBR) of 3 L using methanol for denitrification due to the lack of a readily biodegradable organic carbon source. Process kinetics were compared through the specific Ammonium Uptake Rate (sAUR) finding the appropriate operational sequence at 32ºC with an 8 hour cycle length. Every operational cycle was carried out with a solid retention time (SRT) of 11 days, hydraulic retention time (HRT) of 1 day and 2500 mg VSS L-1. In order to avoid nitrate formation, and thus to save costs, the oxygen concentration was maintained below 1 mg L-1 during the aerobic periods and pH remained within an optimal range (7.5-8.5) alternating different aerobic/anoxic sub-cycles inside the operational cycle. The total nitrogen removal was 0.8-0.9 kg N day-1 m-3. In order to make the process more economical metanol was substitute for the primary hidrolysate of the own WWTP obtaining a total nitrogen removal of 0.7 kg N day-1 m-3. The use of primary hidrolysate would lead to a cost reduction of 0.2-0.3 kg -1 N removed.<br/>The next step was to compare the SBR technology to obtain the nitrite route with the continuous technology using a chemostat reactor. In that a chemostat SHARON (Single-reactor High activity Ammonia Removal Over Nitrite) continuous reactor (4 L) was operated to develop the biological nitrogen removal via nitrite of reject water at 33 ºC. Methanol was added for denitrification In the same chemostat took place nitrification and denitrification alternating periods of 1 hour with a total HRT of 2. As a conclusion, the SBR would be a slightly cheaper process (1.01 versus 1.28 kg -1 N) due to the higher volumetric reaction rates and the SHARON process is a more stable system.

Keywords

Dentrificació; Nitrificació; Clavegueram; Tecnologia de depuració d'aigues

Subjects

628 - Public health engineering. Water. Sanitation. Illuminating engineering

Knowledge Area

Ciències Experimentals i Matemàtiques

Documents

00.AGS_PREVIOUS.pdf

134.4Kb

01.AGS_CHAPTERS_1_TO_12.pdf

6.508Mb

02.AGS_ANNEXES.pdf

653.8Kb

03.AGS_PUBLICATIONS.pdf

113.5Kb

04.AGS_MEMORIA.pdf

115.4Kb

 

Rights

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