ABSTRACT
The removal efficiency of different forms of nitrogen was studied in earthworm ecofilter treating domestic wastewater, and the mechanisms were discussed. Results indicated that, the major form of total nitrogen (TN) in influent water and effluent water were existed as ammonia-nitrogen (NH4+ -N) and nitrate-nitrogen (NO3- -N), respectively. NH4+ -N /TN in influent water and NO3- -N /TN in effluent water were 83.88% and 76.46%, respectively, NH4+ -N decreased and NO3- -N increased during the process. The average removal efficiency of TN and NH4+ -N were 28.08% and 90.44%, respectively, nitrate-nitrogen accumulated massively and nitrite-nitrogen (NO2- -N) accumulated a little. It was also observed that nitrification in earthworm ecofilter was strong and the denitrification was inhibited, TN removal was not as obvious as the NH4+ -N removal due to the poor denitrification environment. The overall removal of TN can be improved by increasing wet/dry ratio, modifying the structure of filter, multistage filter series, following by constructed wetland, and increasing C/N ratio of the influent water.
Subject(s)
Ecosystem , Nitrogen/isolation & purification , Oligochaeta/metabolism , Waste Disposal, Fluid/methods , Wetlands , Animals , Biodegradation, Environmental , Filtration/methods , Quaternary Ammonium Compounds/chemistry , Quaternary Ammonium Compounds/isolation & purification , Water Pollutants, Chemical/isolation & purification , Water Purification/methodsABSTRACT
OBJECTIVE: Endothelin 1 has many biological activities including regulating the functions of auditory system. The present study aimed to investigate the expression of the endothelin receptors in spiral ganglion neurons and its significance in the auditory transmission. METHODS: The cochleae of healthy guinea pigs were fixed, decalcified, embedded in paraffin and serially sectioned. The expression of endothelin receptor subunits, ET receptor A (ET-A) and ET receptor B (ET-B), was examined in the spiral ganglion neurons of guinea pig using immunohistochemical technique. RESULTS: Different degrees of ET-A and ET-B positive reactivity appeared in all spiral ganglion neurons from the basal turn to the apical turn. CONCLUSIONS: These findings support the suggestion that endothelin via the endothelin receptor may play a physiological role in the spiral ganglion neurons.
