International Journal of Microbiology and Immunology Research Vol. 2(3), pp. 041-047, May 2014 ISSN 2327-7769 ©2014 Academe Research Journals

Full Length Research Paper

Effect of various ORP on excess sludge reduction in oxic-settling-anaerobic batch-activated sludge

Afshin Takdastan¹, Naser Mehrdadi² and Azadeh Eslami³*

¹Department of Environmental Health and Environmental Technologies Research Centre, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.

²Department of Environmental Engineering, Environmental Faculty, University of Tehran, Tehran, Iran.

³Department of Environmental Engineering, College of Environment and Energy, Tehran Science and Research Branch, Islamic Azad University, Tehran, Iran. 

*Corresponding author. E-mail: eslami532@yahoo.com. Tel: 09166054619. Fax: +986113342262.

Accepted 6 May, 2014

Abstract

Studies were carried out in two SBR reactors, which were controlled online. After presenting a stable situation in the reactors, during 24 months of the study, sampling and examining of COD, MLSS, MLVSS, pH, DO, SOUR, SVI, ORP and biomass yield (Y) were implemented. The results showed that maximum COD removal efficiency (95%) wad achieved in 10 days retention time and average biomass yield (Y) and K_d were 0.58 (mg biomass/mg COD) and 0.058 (l/day) respectively. After 7 h of the sludge retention time at ORP of -238 mV, the biomass yield (Y) decreased from 0.62 to 0.25 mg biomass/mg COD. Consequently, the excess sludge decreases up to 60%. In this method, the amount of effluent COD is less than the amount of environmental standards of Iran for discharge into surface water and irrigation uses. On the other hand, at the ORP of -238 mV, the amount of SOUR and SVI reached 22 mgO₂/h.g VSS and 40 ml/g respectively.

Key words: Biomass yield, excess sludge reduction, ORP, OSA, sequencing batch reactor.