Skip to Main content Skip to Navigation
New interface
Theses

Optimisation du traitement de l'azote et du phosphore des eaux usées domestiques adapté aux filtres plantés de roseaux

Abstract : Nutrient (phosphorus and nitrogen) discharges from wastewater lead to water quality degradation (74 % of the total French territory in 2006). According to the actual situation, the French government has adopted a Water Framework on December 30, 2006 to achieve a“good ecological status of water” in 2015. Therefore,more stringent standards on nutrients removal for raw wastewater treatment plants are expected (down to 15mg TN.L-1 and 2 mg TP.L-1). However, standards actually remain under the responsibility of departmental authorities according to the water quality of the receiving environment. Since 1990s, Vertical Flow Constructed Wetlands(VFCWs) have been more and more popular in treating raw domestic wastewater for small collectivities of less than 2000 person equivalent (> 2500 units in 2012). However, nitrogen and phosphorus removal are limited in VFCWs (70-80 mg TN.L-1; > 10 mg TP.L-1) according to the new legislation. The aim of this work was on the one hand to implement a recirculation of treated effluent on a VFCW for better nitrogen removal and on the other to use reactive materials to improve phosphorus removal. The experimental scientific approach consisted in monitoring both laboratory and field pilot scale systems under process conditions during 2 years. Treatment and hydraulic performances were monitored over time. Two VFCWs (2,5 m²) filled with expanded schist (Mayennite®) were fed with raw domestic wastewater. The effect of a saturated layer and of the recirculation of treated effluent were studied. Results showed that 38 % of a saturated layer and 100 % of recirculation enabled to improve nitrogen treatment performances (< 20 mgTKN.L-1; < 45 mg TN.L-1) and to meet the French standard D4. Electric arc furnace slags were selected as reactive materials to improve phosphorus treatment performance of the VFCWs in laboratory and field pilot scale systems. Five laboratory-scale column experiments (6L) were fed with a phosphorus synthetic effluent then with a secondary effluent. Four horizontal subsurface flow active filters (0,3 m²; 34 L) were fed with a secondary effluent. The main results showed : (i)differences exist between laboratory and pilot scale regarding treatment performance (< 2 mg P.L-1 during20 months in the laboratory ; seasonal variations at pilot scale) and removal mechanisms (adsorption/precipitation Ca-P in laboratory ; Ca-P + Fe-P at pilot scale), (ii) an increase of temperature (> 15°C) and/or hydraulic retention time (more than 2 days) improved the kinetics of phosphorus removal at pilot scale, (iii) the active filter implementing is limited by the discharge standard required (> 3 mg PTOT.L-1) and the distance to the steel factory (transport costs).
Complete list of metadata

Cited literature [162 references]  Display  Hide  Download

https://theses.hal.science/tel-00809593
Contributor : ABES STAR :  Contact
Submitted on : Tuesday, April 9, 2013 - 3:43:12 PM
Last modification on : Wednesday, April 27, 2022 - 3:56:37 AM
Long-term archiving on: : Wednesday, July 10, 2013 - 8:06:08 AM

File

Prigent_S_10_2012Diffusion.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-00809593, version 1

Citation

Stephane Prigent. Optimisation du traitement de l'azote et du phosphore des eaux usées domestiques adapté aux filtres plantés de roseaux. Génie des procédés. Ecole des Mines de Nantes, 2012. Français. ⟨NNT : 2012EMNA0047⟩. ⟨tel-00809593⟩

Share

Metrics

Record views

1846

Files downloads

6231