No abstract

An enrichment culture was established to isolate a thermophilic hydrocarbon-degrading bacterium from contaminated soil samples from the Tehran Petroleum Refinery. The bacterium was characterized based on 16S rRNA and identified as Brevibacillus borstelensis TMU30. It is registered at NCBI under accession number KF181624.1. The capability of the bacterium for degradation of heptadecane as a representative contaminant in polluted dune sand was evaluated in a slurry bubble column bioreactor. The aeration rate, inoculum content and pulp density were optimized to maximize the degradation of heptadecane using the central composite design of response surface methodology. The results showed that maximum heptadecane reduction reached 48% at an aeration rate of 62 ml min À1 , inoculum content of 9.3% (v/v) and pulp density of 63 g l À1 only after 4 days. This study highlights an important potential use of thermophilic degradative bacteria to eliminate contamination in a slurry bioreactor while shortening dramatically the treatment time.

No abstract

High energy costs, organic carbon availability, and space limitation are some of the barriers faced by wastewater treatment processes. This research investigates the impact of membrane aeration mode, scouring intensity, and loading rate in a single-stage total nitrogen removal process in a membrane aerated biofilm reactor (MABR). Under ammonia loading of 2.7 g N/m2.d, continuous process aeration led to 1.7 g NH4-N/m2.d and 0.8 g TN/m2.d removal, respectively. Conversely, intermittent (5/12 min on/off) aeration resulted in 35% less ammonia removal but 34% higher total nitrogen (TN) removal. The MABR under ammonia load of 1.6 g N/m2.d showed an enhanced effluent quality with an average of 2.5 mg/L effluent ammonia concentration. This finding highlights the nitrification potential of a flow-through MABR as a standalone treatment step without any downstream process. Also, slough-off, a common issue in the biofilm process and was hypothesized to reduce the removal efficiency, showed increased ammonia removal rates by 20%. The microbial analysis indicated the dominant AOB and NOB species as Nitrosomonas spp. and Nitrospira spp, respectively. Moreover, the relative abundance of denitrifying bacteria (40.5%) were found twice in intermittently-aerated MABR compared to the continuously-aerated one (20.5%). However, NOB and denitrifying bacteria relative abundances were comparable where continuous air was supplied.