Sharon / Anammox Process
Sheets

13-jun-2006, STOWA

 

 

Country

 

The Netherlands

Stage of development

Full scale

Process  -

Line

Sludge

 

Function

Nitrogen removal

 

Input

Reject water

 

Concept

Nitrification - Denitrification

Keywords: decrease energy demand; decrease use of chemicals; sludge line; nitrogen removal

 

 

Background

Nitrogen balance of WWTP's shows that a significant internal nitrogen load is recycled in reject water from sludge digestion to the main wastewater treatment. By separate treatment of this reject water the overall nitrogen load of the activated sludge  process can be considerably reduced.

The Sharon/Anammox process is a nitrogen removal system for reject water from sludge de-watering facilities and other ammonia-rich wastewater streams. The process combines two technologies, which were developed independently. The Sharon process is described on the separate fact sheet Sharon process. The Anammox process in combination with the Sharon process will be described hereafter.

Anammox stands for 'Anaerobic ammonium oxidation'. Sharon is an acronym for 'Single reactor for High activity Ammonia Removal Over Nitrite'. Both processes were discovered and developed in the early 1990s at the Technical University of Delft.

 

Description and working principle

The Sharon/Anammox process achieves nitrogen removal by combining two separate treatment steps: a partial nitrification process (Sharon) followed by an anaerobic ammonium oxidation process (Anammox).

Treatment step 1: Sharon process

The Sharon process is used to produce an ammonium-nitrite mixture converting only 50% of the ammonium to nitrite:

NH4+ + HCO3- + 0,75 O2  Ş 0,5 NO2-+ 0,5 NH4+ + CO2 + 1,5 H2O

The conversion takes place in a single, completely mixed reactor without biomass retention at average process temperatures between 30 and 40°C, and retention times of 1 to 2 days.

To ensure that only 50% of the ammonium are converted to nitrite, the oxygen supply is limited. The Sharon reactor can be operated either under alternating oxic and anoxic conditions, or continuously with limited oxygen supply. In the latter case, oxygen consumption by the nitrifying organisms will also generate the anoxic process conditions required for the second treatment step - the Anammox process.

More information on the Sharon process can be found in the separate fact sheet 'Sharon process'.

Treatment step 2: Anammox process

In this treatment step the ammonium-nitrite mixture produced in the Sharon reactor is converted under anoxic conditions to nitrogen gas with ammonium as electron donor. The conversion of ammonium and nitrite to nitrogen gas is described by the following formula:

NO2- + NH4 Ş N2 + 2 H20

The bacteria catalysing the reaction are autotrophic and facilitate the conversion without the use of COD or the addition of external carbon sources. The bacteria capable of catalysing the Anammox reaction can be obtained from a common sludge source.

However, these bacteria have a rather low growth rate, with a doubling time in the order of 10 days at 30°C. The Anammox reactor should therefore be designed with an efficient biomass retention in order to prevent wash-out of the slow-growing Anammox bacteria. In pilot trials sequenced batch reactors were used. Regarding the good granule formation capacity of the bacteria the use of gas-lift-loop reactors has been proposed to ensure efficient mass transfer, mixing and biomass retention on a compact footprint [5].

More technical details on the patented Anammox process can be found in the patent WO9807664.

In the following picture, the treatment sequence of the combined Sharon/Anammox process is schematically depicted.

Sharon/Anammox - process scheme[4]

 

Design guidelines / Technical data

General design

In the table below indicative parameters are given for a full-scale Sharon-Anammox process [1]. When waste activated sludge is digested without thickening the ammonium concentration in case 1 is expected. Sludge thickening and de-watering before digestion will result in higher concentrations (lower flow rates).

 

Parameter

Unit

Case 1

Case 2

General

N-load

kgN/d

1.200

1.200

 

NH4-conc.

kgN/m3

500

1200

 

Influent flow

m3/d

2.400

1.000

Sharon reactor

Volume

m3

3.120

1.300

 

Oxygen demand

kg O2/d

2.180

2.180

 

Air demand

N m3/d

56.000

56.000

Anammox: mov. bed reactor

Volume

m3

450

450

 

HRT

h

4,5

11

Anammox: granular sludge

Volume

m3

75

75

 

HRT

h

0,57

1,8

 

WWTP Dokhaven (Rotterdam, The Netherlands)

A Sharon reactor has been installed on the WWTP in 1998 and was succesfullly operated from 1998 until mid 2002 (see fact sheet on the Sharon process). In 2002 an Anammox reactor was built to realise the combined Sharon/Anammox concept. The Anammox reactor has been designed similar to anaerobic granular sludge reactors. The installation was started up in June 2002.

 

Performance

General performance

Comparison to conventional nitrification/denitrification route

By using the combined Sharon/Anammox process a reduction of up to 60% of the oxygen and energy demand can be realised compared to the traditional nitrification/denitrification route via nitrate. The process combination does not require the presence of organic COD for denitrification. The process combination is considered to be more sustainable than conventional treatment, not the least because of the reduced CO2 emissions associated with the energy savings.

An overall nitrogen removal efficiency of 90 to 95% can be achieved, depending on process conditions and influent characteristics [4].

 

Operational stability and maintenance

The Sharon and Anammox have to be operated under different process conditions. Information on process conditions of the Sharon process can be found on the separate fact sheet 'Sharon process'.

A few remarks were made by [1] regarding the Anammox process:

·       washed-out biomass from the Sharon reactor has no influence on the activity of the Anammox bacteria

·       long start-up times are required with stable operating conditions

·       pH (7- 8,5) and temperature (30 - 37°C) have to be controlled to avoid shock loading and loss of active biomass

 

Capital and operating cost

The investment costs for an Sharon/Anammox installation with a capacity of 1.200 kg NH4-N/day are estimated at 2 mio. euros (2001). The operating costs are linked to the costs for energy, methanol, and lye.

In the table below indicative economical parameters are given for a full-scale Sharon-Anammox process [1]. The cases refer to the dimensioning given in the table Design guidelines / Technical data. (Price level 2001)

Parameter

Unit

Case 1

Case 2

N-load

kgN/d

1.200

1.200

Flow rate

m3/d

2.400

1.000

NH4-conc.

m3/d

500

1.200

Investment

euro (x1000)

2.260

1.810

Depreciation

euro/year (x1000)

240

196

Maintenance

   "

46

41

Personnel

   "

11

11

Electricity

   "

82

76

Total cost

   "

374

325

Cost per kgNremoved

euro

1,05

0,90

 

 

Reference installations

WWTP Dokhaven (NL) (470.000 p.e.) (2002) (Sharon/Anammox)

 

 

 

 

 

 

 

Suppliers / Patents

The Anammox process has been developed and patented by Technical University of Delft, Department of Biotechnology (Bioprocess Technology) - patent number WO9807664.

Delft University of Technology - Faculty of Applied Sciences (Kluyver Laboratory for Biotechnology)

Julianalaan 67  -  2628 BC Delft  -  The Netherlands

Tel.: +31 15 278 2342 - Fax : +31 15 278 2355 - E-mail: bpt@tnw.tudelft.nl  -  Web: www.bt.tudelft.nl/content/bpt/

The Sharon process was developed by Grontmij Consulting Engineers in co-operation with the Technical University of Delft and the Water Authorities of ZHEW and HDSR. Grontmij Consulting Engineers holds the patent on the process design - patent number EP826639.

Grontmij Consulting Engineers

P.O. Box 203  -  3730 AE De Bilt  - The Netherlands

Tel: +31 30 2207 911 -  Fax: +31 30 220 01 74  -  E-mail: communicatie@grontmij.nl  -  Web: www.grontmij.nl

Paques BV has developed a full-scale Anammox reactor.

Paques B.V.

P.O. Box 52  -  8560 AB Balk  -  The Netherlands

Tel: +31 514 608 500  -  Fax: +31 514 603 342  -  E-mail: info@paques.nl  -  Web: www.paques.nl

 

Literature references

[1]   van Dongen, U.; Jetten, M.S.M.; Loosdrecht, M.C.M: The Sharon - Anammox process for treatment of ammonium rich  wastewater. Wat Sci Tech, Vol 44 -1, pp 153-160, 2001.

[2]   Stowa report: Treatment of ammonium-rich reject water from sludge digestion using the Anammox process (in Dutch). 96-21. 1996.

[3]   Stowa report: The combined Sharon/Anammox process (in Dutch and English). 00-25. 2000.

[4]   Website owned by TU Delft  -  www.anammox.com/

[5]   Loosdrecht, M.C.M. et.al.: Improving the sustainability of nitrogen removal. Water 21. Dec. 2001.