ABSTRACT
In the last two decades, constructed wetland systems gained increasing interest in wastewater treatment and as such have been intensively studied around the world. While most of the studies showed excellent removal of various pollutants, the exact contribution, in kinetic terms, of its particular components (such as: root, gravel and water) combined with bacteria is almost nonexistent. In the present study, a phenol degrader bacterium identified as Pseudomonas pseudoalcaligenes was isolated from a constructed wetland, and used in an experimental set-up containing: plants and gravel. Phenol removal rate by planktonic and biofilm bacteria (on sterile Zea mays roots and gravel surfaces) was studied. Specific phenol removal rates revealed significant advantage of planktonic cells (1.04 × 10(-9) mg phenol/CFU/h) compared to root and gravel biofilms: 4.59 × 10(-11)-2.04 × 10(-10) and 8.04 × 10(-11)-4.39 × 10(-10) (mg phenol/CFU/h), respectively. In batch cultures, phenol biodegradation kinetic parameters were determined by biomass growth rates and phenol removal as a function of time. Based on Haldane equation, kinetic constants such as µ(max) = 1.15/h, K(s) = 35.4 mg/L and K(i) = 198.6 mg/L fit well phenol removal by P. pseudoalcaligenes. Although P. pseudoalcaligenes planktonic cells showed the highest phenol removal rate, in constructed wetland systems and especially in those with sub-surface flow, it is expected that surface associated microorganisms (biofilms) will provide a much higher contribution in phenol and other organics removal, due to greater bacterial biomass. Factors affecting the performance of planktonic vs. biofilm bacteria in sub-surface flow constructed wetlands are further discussed.
Subject(s)
Biofilms , Phenol/metabolism , Plankton/metabolism , Plant Roots/microbiology , Pseudomonas pseudoalcaligenes/metabolism , Soil , Wetlands , Biodegradation, Environmental , Biomass , Kinetics , Microscopy, Confocal , Molecular Sequence Data , Phenol/isolation & purification , Phylogeny , Pseudomonas pseudoalcaligenes/genetics , Pseudomonas pseudoalcaligenes/growth & development , Pseudomonas pseudoalcaligenes/isolation & purification , RNA, Ribosomal, 16S/genetics , Time FactorsABSTRACT
The capillary instability of a liquid crystalline cylinder in magnetic field is considered using an energy approach. The boundary problem is solved in the linear approximation of the anisotropy chi(a) of the magnetic susceptibility chi. The effect of anisotropy, in the region 1>> chi > chi(a) >> chi2, can be strong enough to counteract and even reverse the tendency of the field to enhance stabilization by enlarging the cutoff wave number k(s) beyond the conventional one set by Rayleigh.
