This work aimed to evaluate the effects of using three different substrates in the semi-hydroponic culture of lettuce (Lactuca sativa L.) using two different nutrient solutions. A first trial was performed with a nutrient solution rich in macronutrients and micronutrients suitable for lettuce culture, and a second trial with a nutrient solution with pretreated wastewater from effluents of a cheese factory. The experimental design was in randomized blocks with three repetitions and three substrates were used: perlite, coconut fiber, and expanded clay, in both trials. The following parameters were observed: number of leaves, diameter of the cabbage, fresh and dry weight of the aerial part, chlorophyll index and mineral composition of the lettuce. For the first trial, the highest result for the number of leaves (20 leaves), fresh weight (142.0 g) and dry weight (7.2 g) of the aerial part was obtained in the plants growing on perlite. In the second trial, the highest result for the number of leaves (28 leaves), diameter of cabbage (26.7 cm), fresh weight (118.8 g) and dry weight (9.5 g) of the aerial part were achieved by the plants that were grown in coconut fiber. The nutrient solutions were analyzed after each irrigation cycle to verify the possibility of their discharge into the environment. Several parameters were analyzed: pH, conductivity, redox potential, nitrates, nitrites, ammoniacal nitrogen, chlorides, hardness, calcium, phosphates, sodium, potassium, chemical oxygen demand (COD) and magnesium. Ammoniacal nitrogen was found to be the only nutrient that can limits the discharge of nutrient solutions into the environment. It was also proven that the plants, besides obtaining the nutrients necessary for their development in the semi-hydroponic system with the nutrient solution with pre-treated residual water, also functioned as a purification system, allowing the said nutrient solution to be discharged into the environment at the end of each cycle.

The world has never been more developed, yet humanity is on the brink of irreversible environmental loss. Despite the urgency of the situation, there is a limited body of studies addressing environmental concerns in higher education institution, particularly in developing countries, i.e., Saudi Arabia. Sustainable development is the only viable solution, albeit it requires the courage to initiate and sustain efforts dedicated to preserving the environment for the well-being of future generation. The article delves into this issue and examines the impact of environmental education program (EEP) on environmental performance (EP) via waste minimization behaviour (WMB). The research involved meticulous data collection from a sample of 597 students, representing diverse genders and academic specialties at the esteemed public university—King Faisal University (KFU) in Saudi Arabia. The study used statistical software (including SPSS and AMOS, v 25) for rigorous analysis and revealed significant findings. Firstly, the study showed a significant and positive relationship between EEP and EP. Secondly, it revealed a significant and positive association between EEP and WMB. Thirdly, the study ascertained a significant and positive association between WMB and EP. Finally, the study found that the relationship between EEP and EP remains significant even after presenting WMB as a mediator, proposing that WMB has a partial mediation role between EEP and EP. The results highlighted the significance role of EEP in stimulating WMB and achieving EP in the Saudi universities, which contributes to national initiative of green Saudia.

The paper at hand analyses the principal-agent relationship, where comparative perspective between principals’ (municipalities) and agents’ (public utility providers) in the field of water and wastewater management is scrutinized. The goal of the paper is twofold: firstly, to present empirical results validating principal-agent relationships that emerged due to the reorganization process of public enterprises; secondly, to highlight the similarities and differences between the perspectives of principals and agents regarding motives, advantages and disadvantages, and price-setting in relation to the reorganization process. The empirical research is based on the primary data collected through two self-prepared and structured online questionnaires—one for municipalities, and the other for public utility providers. The results reveal similarities between public enterprises and municipalities in motivating factors for full municipal ownership. However, differences are seen among the advantages of the reorganization process. Price-setting by public utilities is recognized as a motivating mechanism for agents.

Over the last few decades, demographic growth combined with poorly controlled urbanization has confronted African cities with a variety of environmental protection challenges. As part of a gradual awareness-raising process, African countries have ratified conventions and adopted a series of laws to protect the environment. Since independence (1960), Gabon has adopted legal instruments to provide a better framework for environmental protection. Despite the existence of well-developed legislation, the Libreville conurbation faces difficulties in waste management. This situation contributes to the degradation of the coastal zone. This study aims to analyse stakeholders’ perceptions of environmental protection regulations in solid waste management practices along the coastline of the Libreville metropolitan area in Gabon. The methodology includes documentary research, field observations, and surveys of 300 study area participants. The results show that the degradation of the coastline is due to a lack of awareness and compliance with the laws governing environmental protection and waste management. As a result, waste disposal practices such as dumping in nature, waterways, illegal dumps, and gutters are commonplace among the population. To achieve sustainable coastal zone management, it is essential to apply regulatory texts and involve stakeholders in improving planning and the quality of the coastal environment.