Volume 17 [2015]

The aim of this paper is to highlight the way towards the exploitation of treated wastewater for food crops production in order to cope with the acute water scarcity and its hazardous consequences. Reclaimed water reuse has not been practiced in Tobruk, and hence, lack of relevant data and information was the major difficulty in carrying out this research. The existing sewage treatment plant in Tobruk city produces about 7,000 cubic meters per day of suitable effluent for agricultural irrigation and safe discharge. This proportion is worth twice as much as the water being currently used for irrigation. Therefore, with proper planning and management, treated wastewater reuse schemes, in addition to their economical and environmental benefits, can be an efficient mechanism to cope with water shortage and reducing the high burden placed on the desalination plant. Wastewater reuse is considered as a reliable, secure, and drought-resistant water source. Owing to the lack of disinfection processes and routinely monitoring data, there is uncertainty concerning the microbiological safety and quality of the treated effluent. Public perception might be the major challenge facing the planning for a reuse scheme as 51 % of the population of Tobruk have shown their reluctance to consume food crops irrigated with treated wastewater. Nonetheless, public attitudes can be fostered by awareness through the media as some people, when the issue was discussed, have shown a positive response. In fact their main concerns were related to public health safety and potential negative environmental impacts which can be addressed through good planning and prudent management.

Nitrate is a common groundwater pollutant all over the world. In some regions of Iran, its levels are high enough to cause serious problems to human health and the environment. The objectives of this work were to evaluate the efficiency of Fe-doped TiO₂ nanoparticles at removing nitrate from aqueous solutions under UV and solar radiation and to model nitrate removal using response surface methodology techniques. In this study, a response surface methodology based on the Box–Behnken design matrix was used to describe the process of nitrate removal from an aqueous solution with four independent parameters, namely Fe-doped TiO₂ (dose 1-2 g l^-1), nitrate concentration (25-100 mg l^-1), contact time (10-120 min), and pH (4-9). The results indicated that the removal efficiency of nitrate in the presence of ultraviolet and solar radiation was 56.5 % and 21.8%, respectively. The removal efficiency of nitrate increased with time and initial concentration of nitrate. Analysis of variance (ANOVA) indicated that the proposed model was essentially in accordance with the experimental results with the correlation coefficient R² = 0.9237 and Adj-R² = 0.8347. Response surface methodology (RSM) proved to be a powerful statistical tool for investigating the operating conditions for nitrate removal under UV irradiation.

Activated sludge is a biological floc composed of microorganisms, organics, and inorganics and plays an important role in wastewater treatment. The pH of an activated sludge suspension determines the acid – base behaviour and the charge of the microorganisms in water. In the present study, the determination of acid – base behaviour of activated sludge was performed using microelectrophoresis and Potentiometric Mass Titrations (PMT). For activated sludge that is a complicated biological system, direct microelectrophoresis is not a suitable method for the determination of its ζ-potential. This method leads to a variety of isoelectric point (iep) values due to the presence of different microorganisms in activated sludge. On the contrary, the PMT method used for the first time for activated sludge can provide the overall point of zero charge (pzc) value that is 8.2. In addition, a simple methodology is proposed for the quantitative determination of the overall solid charge as a function of solution pH, which requires only (a) the titration curves of an electrolyte suspension and of the blank electrolyte solution and (b) the calculation of the H⁺ ions consumed for the above titration curves. 

Long term seasonal wind speeds were found to be relatively higher during the period from January to September. At the other hand, higher wind speeds were observed between the period between 06:00 and 18:00 in the day. These periods feet well with annual and daily periods of maximum demand of electricity, respectively.