Identification et traitement des polluants émergents dans les eaux usées urbaines

الموضوعات

علوم تطبيقية وتكنولوجية

الملخص

In arid Mediterranean countries, such as Tunisia, wastewater must be valued as an alternative and non-conventional source of water resources. Since the problem of water scarcity, the high salinity of groundwater, and the pollution of water bodies, can cause several problems to humanity fresh-water demand. Furthermore, the main factor behind water stress, which can affect the water demand, is the agriculture sector, which is the major user of the world’s freshwater. Therefore, the reuse of effluents from wastewater treatment plants (WWTPs) is becoming an increasingly widespread and necessary alternative to conventional water sources in these countries. To do that, WWTPs effluents must have a high quality, and must be free of all hazardous pollutants that cause negative effects on crops (when using water for irrigation), in water and aquatic organisms and, consequently, on human health as well. In this regard, there is an increasing environmental concern about emerging contaminants or micropollutants nowadays, those escape from the conventional treatment plants, and release into the environment and found at very low concentrations of the order of μg L-1to ng L-1. Thus, the development of tertiary treatments for micropollutant removal is becoming a great interest.It is in this context that this Ph.D. thesis is aimed to apply one of the most efficient and environmentally sustainable advancedoxidation processes (AOPs), the solarphoto-Fenton process, for wastewater treatment. In the first part, this study investigated the use of solar photo-Fenton process in raceway pond reactor (RPRs), to treat simulated secondary effluent from a Tunisian urban wastewater treatment plant (WWTP), with high chloride load. To this end, a mixture of three contaminants of emerging concern (CECs) was used as model pollutants at 50 μg/L each (one antibiotic, sulfamethoxazole and two pesticides, pirimicarb and imidacloprid). All the assays were conducted at neutral pH with 0.1 mM Fe3+:EDDS at 1:1 molar ratio. The effect of hydrogen peroxide initial concentration (20, 30, and 90 mg L-1) on microcontaminant removal was studied. Different liquid depths (5 and 15 cm) were selected to assess the relationship between the microcontaminant removal and the volumetric rate of photon absorption (VRPA). Although the reaction rate was initially photolimited, after a short reaction time of 15 min, the final yield (≈ 80%of CEC removal) was limited by the photo-degradation of the Fe3+:EDDS complex and excess H2O2 was found at all concentrations used. Therefore, treatment times below 15min should be used. The treatment capacity was three times higher when the liquid depth was increased from 5 to 15 cm. For the first time, these results show that the operation of a 15 cm-deep RPR in continuous flow mode would be suitable for large-scale implementation of the solar photo-Fenton process.In the second part of this work, a kinetic study of the solar photo-Fenton process at neutral pH mediated by the Fe3+-NTA complex (molar ratio 1: 1) applied to remove contaminants of emerging concern (CECs). To this end, wastewater treatment plant (WWTP) secondary effluents were treated in a raceway pond reactor (RPR) at pilot plant scale with 0.1 mM Fe3+-NTA and 0.88 mM H2O2under average solar UVA irradiance of 35 W/m2. Sulfamethoxazole and imidacloprid, at 50 μg L-1of initial concentration each, were selected as model CECs. Up to 40% of the sum of both model CECs was removed from simulated WWTP effluent by the Fe3+-NTA Fenton-like process, and >80% was removed by solar photo-Fenton. The effect of liquid depth in the reactor was evaluated, showing an increase of the treatment capacity from 12 mg CEC/m2·h to 18 mg CEC/m2·h when liquid depth increased from 5 to 15 cm. Afterwards, these results were validated with real WWTP effluents and compared with the results obtained with the Fe3+-EDDS complex under the same operating conditions. The same CEC removal rates were obtained with Fe3+-NTA and Fe3+-EDDS at 5 cm of liquid depth (kinetic constants of 0.110 min−1and 0.046 min−1for sulfamethoxazole and imidacloprid, respectively). Conversely, at 15 cm of liquid depth, the degradation rates were lower with Fe3+-NTA (kinetic constants of 0.034 min−1for sulfamethoxazole and 0.017 min−1for imidacloprid), whereas with Fe3+-EDDS the values were 0.076 min−1 and 0.047 min−1for sulfamethoxazole and imidacloprid, respectively. Regarding process cost estimation, the use of NTA as iron chelate for solar photo-Fenton at neutral pH at pilot plant scale resulted very cost-effective (0.13–0.14 €/m3) in comparison with the use of EDDS (0.46–0.48 €/m3) at the two liquid depths tested.

روابط وملفات

التعريف والنوع

رقم الوثيقة

0ffb117e-c6d2-4055-8fbc-840a3ab96af4

رقم العقد

0

نوع الوسائط

Crawler

نوع المحتوى

الرسائل العلمية

صيغة المصدر

رسائل دكتوراة

نوع الملف

pdf image

أسماء الملفات

0ffb117e-c6d2-4055-8fbc-840a3ab96af4_1.pdf

بيانات النشر

ألقاب المؤلفين

[{"name_ar":"Amal Mejri","title_ar":"اعداد","title_en":"Preparation"},{"name_ar":"Ismail Trabelsi","title_ar":"اشراف","title_en":"Supervision"}]

اللغة

English

المصدر والدورية

اسم المصدر

Identification et traitement des polluants émergents dans les eaux usées urbaines

المحتوى والصفحات

عدد الصفحات

0

إشراف وإعداد

الإشراف

Ismail Trabelsi

الإعداد

Amal Mejri

الاقتباسات الببليوغرافية