Use of Tetrazolium Salt INT for Estimation of Biological Activity of Activated Sludge Cultivated in SBR Process

The tetrazolium salt 2-( 4-Iodophenyl)-3-( 4-nitrophenyl)-5-phenyltetrazolium chloride( INT) was used as a tool for estimating the activity of the electron transport system( ETS) in activated sludge in a 40 L sequencing batch reactor( SBR) and domestic sewage as the organic substrate. The activity of INT-ETS during one SBR cycle,and the effect of the ammonia concentration and the concentration of organic matter influent on the INT-ETS activity were investigated. The results show that: the use of INT is reliable in estimating of biological activity of activated sludge of SBR system; Biological activity of organic matter biodegradation, nitrification and denitrification process in SBR system reduce orderly. Obviously,INT-ETS activity reduces from 232. 59 mg /( g·h) to 190. 65 mg /( g·h) at first and then decreases to 113. 88 mg /( g·h) when influent concentration of COD and NH4 +-N is 300 mg / L and 40 mg / L respectively. In addition,various influent Nitrogen( NH4 +-N are 14. 5 mg / L and 42. 0 mg / L) and organic shock loading( COD are 293 mg / L and 685 mg / L) experimentations cure prove that operational conditions have no obvious effect on INT-ETS variation rule. However,the time of the appearance of feature points marking different reaction phase is influenced.

Impact of triazophos insecticide on paddy soil environment

A laboratory incubation study was carried out to elucidate the dynamic response of insecticide (triazophos) on a paddy field soil health under controlled moisture (flooded soil) and temperature (25℃). The insecticide was applied at five levels that were 0.0 (control), 0.5 field rate (FR), 1.0 FR, 5.0 FR, and 10.0 FR, where FR was 1500 ml/hm 2, and the parameters were studied at 1, 4, 7, 14, and 21 days after treatments' addition. The electron transport system (ETS)/dehydrogenase activity exhibited a negative correlation with insecticide concentrations, and the activity affected adversely as the concentration increased. The higher doses of 5 and 10 field rates significantly reduced the ETS activity, while lower rates failed to produce any significant inhibiting effect against the control. The toxicity of insecticide decreased towards decreasing the ETS activity with the advancement of incubation period. The insecticide caused an improvement in the soil phenol content and it increased with increasing concentration of insecticide. The insecticide incorporation applied at various concentrations did not produce any significant change in soil protein content and it remained stable throughout the incubation period of 21-days. The response of biomass phospholipid content was nearly similar to ETS activity. The phospholipid content was decreased with the addition of insecticide and the toxicity was in the order: 10 FR (field rate)>5 FR>1.0 FR>0.5 FR>control and it also decreased with incubation period.