Abstract: A Laboratory-scale packed bed reactor with microbial
cellulose as the biofilm carrier was used to investigate the
denitrification of high-strength nitrate wastewater with specific
emphasis on the effect the nitrogen loading rate and hydraulic
retention time. Ethanol was added as a carbon source for
denitrification. As a result of this investigation, it was found that up
to 500 mg/l feed nitrate concentration the present system is able to
produce an effluent with nitrate content below 10 ppm at 3 h
hydraulic retention time. The highest observed denitrification rate
was 4.57 kg NO3-N/ (m3 .d) at a nitrate load of 5.64 kg NO3-
N/(m3 .d), and removal efficiencies higher than 90% were obtained
for loads up to 4.2 kg NO3-N/(m3 .d). A mass relation between COD
consumed and NO3-N removed around 2.82 was observed. This
continuous-flow bioreactor proved an efficient denitrification system
with a relatively low retention time.
Abstract: Nitrogen loss from irrigated cropland, particularly
sandy soils, significantly contributes to nitrate (NO3
-) levels in
surface and groundwaters. Thus, it is of great interest to use
inexpensive natural products that can increase the fertilizer efficiency
and decrease nitrate leaching. In this study, the ability of natural
Iranian zeolite clinoptilolite (Cp) and surfactant modified zeolite
clinoptilolite (SMZ) to remove NH4
+ and NO3
-, respectively, from
aqueous solutions was determined. The feasibility of using Cp and
SMZ as soil amendment to reduce nitrate leaching from soil using
lysimeters was also investigated. Zeolite showed 10.23% to 88.42%
NH4
+ removal efficiency over a wide range of initial NH4
+
concentrations. Nitrate removal efficiency by SMZ was 32.26% to
82.26%. Field study results showed that Cp and SMZ significantly (p
< 0.05) reduced leachate NO3-N concentration compared to control.
There was no significant difference between maximum and mean
leachate NO3-N concentration of SMZ lysimeters and those of Cp
lysimeters.