Groundwater quality assessment for different uses using various water quality indices in semi-arid region of central Tunisia

Environmental Science and Pollution Research - The Hajeb Layoun-Jelma basin, located in the central Tunisia, is the principal source of water supply for Sidi Bouzid and Sfax region. The...     

Modeling of secondary treated wastewater disinfection by UV irradiation: Effects of suspended solids content

This work aimed to study UV-resistant strains of Pseudomonas aeruginosa, to propose a formulation of the kinetics of secondary treated wastewater disinfection and to underline the influence of suspended solids on the inactivation kinetics of these strains. Some investigations were carried out for the validation of some simulation models, from the simplest, the kinetics model of Chick-Watson reduced to first order, to rather complex models such as multi-kinetic and Collins-Selleck models. Results revealed that the involved processes of UV irradiation were too complex to be approached by a simplified formulation, even in the case of specific strains of microorganisms and the use of nearly constant UV radiation intensity. In fact, the application of Chick-Watson model in its original form is not representative of the kinetics of UV disinfection. Modification, taking into account the speed change during the disinfection process, has not significantly improved results. On the other hand, the application of Collins-Selleck model demonstrates that it was necessary to exceed a least dose of critical radiation to start the process of inactivation. To better explain the process of inactivation, we have assumed that the action of disinfectant on the survival of lonely microorganisms is faster than its action on suspended solids protected or agglomerated to each others. We can assume in this case the existence of two inactivation kinetics during the processes (parallel and independent) of the first-order. For this reason, the application of a new kinetic model by introducing a third factor reflecting the influence of suspended solids in water on disinfection kinetics appeared to be determinant for modeling UV inactivation of P. aeruginosa in secondary treated wastewater.     

Removal of phosphate ions from aqueous solution using Tunisian clays minerals and synthetic zeolite

Phosphate ions are usually considered to be responsible for the algal bloom in receiving water bodies and aesthetic problems in water. From the environmental point of view, the management of such contaminant and valuable resource is very important. The present work deals with the removal of phosphate ions from aqueous solutions using kaolinitic and smectic clay minerals and synthetic zeolite as adsorbent. The pH effect and adsorption kinetic were studied. It was found that phosphate could be efficiently removed at acidic pH (between 4 and 6) and the second order model of kinetics is more adopted for all samples. The isotherms of adsorption of phosphate ions by the two clays and the zeolite samples show that the zeolite has the highest rate of uptake (52.9 mg P/g). Equilibrium data were well fitted with Langmuir and Freundlich isotherm.     

Improvement of fruit and vegetable waste anaerobic digestion performance and stability with co-substrates addition

The effect of fish waste (FW), abattoir wastewater (AW) and waste activated sludge (WAS) addition as co-substrates on the fruit and vegetable waste (FVW) anaerobic digestion performance was investigated under mesophilic conditions using four anaerobic sequencing batch reactors (ASBR) with the aim of finding the better co-substrate for the enhanced performance of co-digestion. The reactors were operated at an organic loading rate of 2.46–2.51 g volatile solids (VS) l⁻¹ d⁻¹, of which approximately 90% were from FVW, and a hydraulic retention time of 10 days. It was observed that AW and WAS additions with a ratio of 10% VS enhanced biogas yield by 51.5% and 43.8% and total volatile solids removal by 10% and 11.7%, respectively. However FW addition led to improvement of the process stability, as indicated by the low VFAs/Alkalinity ratio of 0.28, and permitted anaerobic digestion of FVW without chemical alkali addition. Despite a considerable decrease in the C/N ratio from 34.2 to 27.6, the addition of FW slightly improved the gas production yield (8.1%) compared to anaerobic digestion of FVW alone. A C/N ratio between 22 and 25 seemed to be better for anaerobic co-digestion of FVW with its co-substrates. The most significant factor for enhanced FVW digestion performance was the improved organic nitrogen content provided by the additional wastes. Consequently, the occurrence of an imbalance between the different groups of anaerobic bacteria which may take place in unstable anaerobic digestion of FVW could be prevented.     

Effects of anthracene, pyrene and benzo[a]pyrene spiking and sewage sludge compost amendment on soil ecotoxicity during a bioremediation process

The fate of spiked anthracene, pyrene and benzo[a]pyrene in soil with or without sewage sludge compost was assessed during a 6-month bioremediation process simulating landfarming. Bioassays and physico-chemical analyses were employed to monitor toxicity change in soil samples and elutriates through ten sampling campaigns. Pearson product-moment correlation coefficient was determined to measure the strength of relationship between bioassays and physico-chemical analyses. The PAH dissipation in soil was enhanced after the first water addition, and the remaining amounts at the end of the experiment were positively correlated to the number of benzene rings and the presence of sewage sludge compost. Toxicity of soil elutriates to Daphnia magna was evident at early stages, originating exclusively from sewage sludge compost amendment. The lettuce root elongation was continuously inhibited by elutriates for all the treatments including control soil, probably due to high salinity or to unaddressed leachable phytotoxic compounds that were present in the experimental soil. The newly developed direct solid-phase chronic toxicity test using ostracod (Heterocypris incongruens) succeeded in evaluating the soil-bound PAH toxicity, as PAHs could not be detected in elutriates.     

Chemical Characteristics of Rain Water at an Urban Site of South Western Turkey

In this study, chemical composition of the rain water in Mugla was investigated from February to April 2002. Rain water samples were obtained from Mugla, a small city in south western Turkey. The Yatagan Power Plant is located 30 km northwest of Mugla city. The values of pH and the concentrations of major ions (Ca²⁺, Na⁺, K⁺, SO₄ ²⁻, NO₃ ⁻, NH₄ ⁺) in the rainwater samples were analyzed. The pH varied from 4.5 to 7.7 with an average of 6.9 which was in alkaline range considering 5.6 as the neutral pH of cloud water with atmospheric CO₂ equilibrium. In the total 30 rain events, only two events were observed in acidic range (< 5.6) which occurred after continuous rains. The equivalent concentration of components followed the order: Ca²⁺ > SO₄ ²⁻ > NH₄ ⁺ > NO₃ ⁻ > Na⁺ > K⁺ > H⁺. The volume-weighted mean (VWM) of the measured ionic sum is 371.62 μeq/l. The ratio of between sum cations and sum anions (∑cations /∑ anions) is 1.52 μeq/l. The alkaline components (Ca²⁺, Na⁺, K⁺) contribute 52%, NH₄ ⁺ 8%, whereas, the contribution from the acidic components is relatively small (40%). The low concentrations of H⁺ found in rainwater samples from Mugla suggest that an important portion of H₂SO₄ and HNO₃ have been neutralized by alkaline particles in the atmosphere. The dust-rich local and surrounding limestone environment might have caused the high concentration of Ca²⁺ in Mugla area. The relatively high concentration of NH₄ ⁺ observed at Mugla is suspected to be due to surrounding agricultural. The results obtained in this study are compared with those other studies conducted at various places in the world.     

Potential of windrow food and green waste composting in Tunisia

Environmental Science and Pollution Research - Solid waste management and disposal is one of the most significant challenges facing urban communities around the world. There is a wide range of...     

Classification of dimension stone wastes

Purpose

For countries in which the stone industry is well developed, opposition to quarry and plant waste is gradually increasing. The primary step for waste control and environmental management is to define the problem of concern. In this study, natural building stone wastes were classified for the first time in the literature.

Methods

Following on-site physical observations and research at more than 50 quarries and 20 plants, stone wastes were classified as (1) solid, (2) dust and (3) semi-slurry, slurry and cake.

Conclusions

As a result of this study, the characteristics of wastes, their main environmental threats and the industries in which wastes could be used were defined for each group.     

Inactivation of biohazards in healthcare wastewater by E-Beam and Gamma irradiation: a comparative study

Environmental Science and Pollution Research - The main objective of this study is to evaluate the effect of irradiation by Gamma rays and Electron Beam (E-Beam) on naturally occurring...