Abstract
In the previous study, it was shown that purification rate and denitrification rate were influenced by different kinds of soil, carbon source and nitrogen concentration in waste water.
But the amount of purification had reduced after 30-40 days from the beginning of the experiments. So the experiment was further repeated in which waste water was supplied intermittently (30 days irrigated-30 days non-irrigated-30 days irrigated) in order to discover the influence of intermittent irrigation for adsorption of soil and the number of denitrifying bacteria.
In this experiment, five factors were changed, i.e., irrigation method (continuous and intermittent), kind of soil (clay loam and Kuroboku soil), carbon source (mixed and unmixed), N-concentration (20 and 100mg/l) and soil water condition (saturated and unsaturated).
The result of this experiment showed that the purification capacity had recovered by decreasing of adsorption amount of soil and increasing of denitrifying bacteria after the resumption of irrigation.
The analytical results of purification rate, adsorption rate and denitrification rate by analysis of variance are summarized as follows:
1. The effective factors for purification rate were the kind of soil, carbon source, N-concentration of incoming water and irrigation method. The mean purification rate of intermittent irrigation was 49%, which had increased 8% more than continuous irrigation.
2. For adsorption rate, the interaction between the kind of soil and N-concentration was shown.
3. All five factors were effective for denitrification rate. The mean denitrification rate of intermittent irrigation was 39%, 8% higher than continuous irrigation.
