Blanca Antizar-Ladislao

Influence of mixture ratio and pH to solidification/stabilization process of hospital solid waste incineration ash in Portland cement

Solidification/stabilization (S/S) is an established utilization technology to treat hazardous wastes. This research explored the influence of pH (3-12) on the immobilization of heavy metals present in five mixtures of hospital solid waste incinerator ash and Portland cement, following two different processes of waste solidification/stabilization (cement hydration and granulation). In general, cement hydration process resulted in more stable products than granulation process. A high ash content in the mixture with Portland cement (60wt%) resulted in the highest immobilization of Pb(2+) and Cu(2+), while a low ash content in the mixture (10wt%) resulted in the lowest leachability of Zn(2+). When ash and Portland cement was mixed in equal proportions (50wt%) the highest encapsulation was observed for Ni(2+), Cd(2+) and Cr(3+). Neutral and weak alkaline pH values within the range pH=7-8 resulted in the lowest leachability of the monitored heavy metals.

Challenges, Options and Future Research Needs

Microorganisms can contribute to solve current global challenges. The use of microorganisms to abate climate change, combat pathogens, improve soil fertility, and produce bioenergy is offering a great potential. Microorganisms facilitate the conversion of organic waste to soil amendment, or compost using composting approaches; where composting of organic waste is already established, the use of compost as a landfill cover to abate green-house gas emission shows to be promising. Bionergy is seen as one of the primary possibilities for preventing climate change. New techniques have been devised for the utilization of second generation biomass feedstock for energy production, including fermentation and anaerobic digestion. It is suggested that further research needs should be oriented towards the improvement of soil quality and fertility, the adaptation of agricultural management and technologies to climate change and the development of renewable energies.