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Accueil du site → Doctorat → Allemagne → 2016 → Optimization of nitrogen removal in various vertical flow constructed wetland designs and application of treated wastewater for reuse in irrigation in Jordan

Brandenburg University of Technology (2016)

Optimization of nitrogen removal in various vertical flow constructed wetland designs and application of treated wastewater for reuse in irrigation in Jordan

Abdallat, Ghaida

Titre : Optimization of nitrogen removal in various vertical flow constructed wetland designs and application of treated wastewater for reuse in irrigation in Jordan

Optimierung der Stickstoffentfernung in verschiedenen vertikalen Strömungspflanzenkläranlage-Designs und Anwendung von gereinigtem Abwasser zur Wiederverwendung in Bewässerung in Jordanien

Auteur : Abdallat, Ghaida

Université de soutenance : Brandenburg University of Technology

Grade : Doctor of Philosophy (Ph.D.) in Environmental Sciences. 2016

Résumé
In arid countries, reclaimed water in irrigation is a widespread practice. Therefore, robust treatment designs are prerequisite to obtain effluent quality that conforms to the legal requirements for reuse and health standards. Vertical flow constructed wetlands (VFCWs) are attractive decentralized treatment plants in many countries and communities. VFCWs are capable of providing adequate treatment for organic and solids removal, even though there are limitations on nutrient and pathogen removal. Within this study, various VFCW systems were investigated, in Germany and Jordan, to optimize nitrogen removal using sustainable and low cost options to guarantee the safe reuse in Jordan. In Germany at Langenreichenbach research facility, two-stage VFCWs planted (Phragmites australis) and unplanted were evaluated and modified to compare the role of plants over two years. Generally, there was no significant role of plants on the treatment performance. Both systems showed high removal efficiency for TOC, BOD5, and TSS over the study period. During the first year of the study, effluent TN concentrations ranged from 60 - 61 mg/L in both systems as a result of high effluent NO3—N concentrations (50 - 52 mg/L). In the second year, the systems were modified, adopting a saturated layer in the 1st stage to enhance denitrification. Average effluent TN concentrations were reduced to 45 mg/L in both systems. In addition, during modifications, the E.coli removal was enhanced in both systems achieving 4 log reduction instead of 2 log reduction during the first year of the study. In Jordan at the Fuhais research facility, two VFCW systems were studied considering category-A (TN : 45 mg/L and NO3-N : 30 mg/L) in the Jordanian Standards for reuse in irrigation (JS 893/2006). Recirculating (ECO-1) and Multi-stage (ECO-2) VFCW designs have shown high removal efficiency of COD, TSS, and BOD5 over three years of monitoring. ECO-1 system combines simultaneous nitrification and denitrification by recycling portion of nitrified effluent into the recirculation tank. However, effluent TN and NO3—N concentrations were 55 and 44 mg/L, respectively, that the system conformed to the JS category-B (TN : 70 mg/L and NO3-N : 45 mg/L) during monitoring phase. Therefore, ECO-1 was modified by installing plastic media in the recirculation tank that attached growth increases the abundance and activity of microorganisms. TN concentration was reduced effectively of 40 mg/L, conforming to the JS category-A, whereas, NO3—N concentration was reduced to 37 mg/L, conforming to the JS category-B. However, over the study period, E.coli concentrations were conformed to the JS category-C (more than 1000 MPN/100 mL).
ECO-2 consists of two unsaturated VFCWs in series ; single-pass unplanted filter followed by planted filter (Phragmites australis). E.coli removal was relatively high before modification that the effluent conformed to the JS (category-B : 1000 MPN/100 mL), achieving 4.4 log reduction. The effluent TN and NO3—N concentrations did not conform to the JS of 77 and 76 mg/L, respectively, due to insufficiency of carbon source to promote denitrification (high BOD5 removal) during monitoring phase of the study. Thus, ECO-2 was modified adopting raw wastewater step-feeding strategy that a specific volume of raw wastewater was mixed with 1st stage effluent in the mixing tank. TN and NO3—N concentrations were reduced to 52 and 50 mg/L, respectively ; conforming to the JS category-B. Whereas, E.coli removal was influenced by E.coli ingress from raw step-feeding, achieving 3.5 log reduction, conforming to the JS category-C.
The short-term impact of irrigation with different water quality and quantity was investigated at the Fuhais site. Soil physicochemical and biological properties in three parallel experimental reuse plots were investigated. The plots were cultivated with lemon trees and were irrigated via a subsurface irrigation system. Moreover, each plot was divided into two subparts (A and B) whereby one part received 11 mm/day of irrigation water and the other received 6 mm/day. Using treated effluent and tap water showed the same trend of increased soli salinity (ECs). Significant difference in ECs, SAR, Mg+2, Ca+2, and Na+ were observed at 0-20 cm as a result of high evaporation and capillary rise that increased salts accumulation in the topsoil. However, using more water reduced the salts accumulation in sub soil layers due to continuous leaching. Whereas, results showed no significant variation in soil texture, structure, moisture, and infiltration rate among reuse plots and subparts. Additionally, results revealed an absence of total coliform, fecal coliform, and E.coli in the irrigated soils, indicating the effectiveness of using subsurface irrigation as a disinfection step for reuse.

Mots Clés : Denitrifikation ; Nitrifikation ; Pflanzenkläranlage ; Stickstoff Constructed wetland ; Denitrification ; Nitrification ; Nitrogen

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