Chapters authored
Downflow Hanging Sponge System: A Self-Sustaining Option for Wastewater Treatment
Need of self-sustaining wastewater treatment plants (WWTPs) has become critical to cope up with dynamics of the environmental regulations and rapid advancements in the contemporary technologies. At present there are limited number of self-sustaining WWTPs around the world. The aim of this chapter is to present state -of- art of Downflow Hanging Sponge (DHS) system which was developed as a post treatment unit of Upflow Anaerobic Sludge Blanket (UASB) from sustainability perspective. DHS system is a non-submerged fixed bed trickling filter (TF) that employs a core technology of polyurethane sponges as a media where the microorganisms thrive and major treatment processes take place. This chapter reviews the introduction of DHS system (UASB+DHS) summarizes the quantitative analysis of environmental, economic and social sustainability using indicators. Furthermore, self-sustaining prospects of DHS system are assessed and discussed by comparing with conventional TF (UASB+TF).
Part of the book: Promising Techniques for Wastewater Treatment and Water Quality Assessment
The Contribution of Autotrophic Nitrogen Oxidizers to Global Nitrogen Conversion
The accumulation of ammonium (NH4+-N) and nitrous oxide (N2O-N) in the environment is causing concern due to their ecological impacts and contribution to global warming. Autotrophic nitrogen oxidizers, including aerobic ammonium-oxidizing archaea and bacteria, anaerobic ammonium oxidizer and nitrite oxidizers, play a crucial role in the nitrogen cycle by facilitating the removal of nitrogenous residues from the environment. Nitrogen oxides (NOx) like nitrite (NO2−-N) and nitrate (NO3−-N) are produced as key immediate products during the conversion of NH4+-N or N2O-N. Additionally, these autotrophic microbes utilize carbon dioxide (CO2) for cell synthesis, thereby mitigating the greenhouse effect. Preliminary results pointed out that nitrogen oxidizers could effectively remove NH4+-N and NOx from sewage and wastewater systems at the loading rate lower than 0.5 kg N/m3-day. Moreover, this family could also reduce the greenhouse N2O-N through oxidizing pathway, attaining the maximum reduction of 25.2-fold the annual N2O production.
Part of the book: Recent Advances on Nitrification and Denitrification