The Use of Phosphate Washing Sludge to Recover by Composting the Leachate from the Controlled Landfill

The percolation of rainwater and runoff water through household waste in the dumpsite generally leads to an overabundance of leachate in Moroccan landfills, which is a source of soil, surface water and groundwater contamination. In order to ecologically solve the problem posed by the leachate in the dump site, to safeguard the environment and to contribute to sustainable development, we have carried out this study which aims to study the possibility of composting leachate with green waste and phosphate washing sludge. Various combinations with five substrates (leachate, green waste, sugar lime sludge, phosphate washing sludge and olive mill wastewater) in different proportions were used to build five windrows. A 24 h contact between the phosphate sludge or sugar lime sludge and the leachate took place prior to the addition of the green waste for the construction of the different windrows. This contact time ensured the absorption of a significant portion of the leachate and the disappearance of bad odor. A significant reduction was obtained with streptococci and mesophilic flora after 24 h of contact. The monitoring of the physicochemical parameters throughout the composting process showed that the temperature of the different windrows followed a good pace presenting all composting phases. Moisture, pH, C/N ratio and the percentage of degradation of the organic matter conformed to the quality standards of the compost. The combinations of the alkaline treatment and the composting process allowed a significant hygienization of the leachate. The results of the humification parameters and the E4/E6 ratio suggest that the composts obtained with phosphate sludge were the most stable and mature and can be used in the agricultural field or green space.

Resilience of humification process to evaluate soil recovery in a semiarid agroecosystem of central Argentina .

Resilience has become a key concept in agricultural management for sustaining soil quality and preventing soil degradation. Land use is a factor that affects soil organic matter (SOM) concentration, distribution and dynamics. In consequence, several recovery practices have been proposed in order to maintain or enhance SOM contents in agroecosystems, such as zero soil disruption (no-till), farm enclosures and crop rotation. We evaluated the efficiency of recovery practices (after a 5-yr period) in reversing SOM losses in a Typic Haplustoll of the central semiarid region of Argentina. A comparative assessment of the resilience of SOM synthesis (humification process) was performed between the recently adopted restorative management and traditional systems (45 years of plow-tillage) using a native woodland as a baseline. In soil samples (0-20 cm), total SOM, its fractions (non-humic substances, humic substances, humic acids, and fulvic acids), and structure (humification index and polymerization index) were analyzed. Degradation rates, recovery rates and soil resilience classes were calculated. Results showed that in our semiarid environment, plowing has significantly affected the resilience of the humification parameters by high degradation rates, whereas the adoption of recovery practices did not reverse ongoing degradative processes. All the analyzed land uses were included in the same resilience class, suggesting that soils have established a new equilibrium (at low values) with high resistance in front of short-term changes. However, a small tendency of minor degradation rates in the farm enclosure site may indicate the beginning of recovery processes.