Purification of exuding water in reclaimed land by combination of irradiation and biological treatment

The dirty water exuding from garbage-filled reclaimed land contains a large quantity of organic contaminating substances. The main component of the contaminating substances is humus called humic acid and fulvic acid. It is difficult to apply biological treatment such as activated sludge process to exuding water because the biological decomposition property of the humus is generally poor. Sufficient effect cannot be expected by physicochemical process such as active carbon treatment and flocculation-precipitation treatment because the molecular weight distribution of the humus is very wide. If irradiation and biological treatment can be combined, the irradiation dose required can be largely reduced. Therefore, exuding water was sampled in Tokyo Bay No.15 reclaimed land, and Co-60 gamma ray was irradiated to see the change of its BOD. The irradiating condition in irradiation-biological treatment was clarified, and the possible method of the combined treatment was decided for trial. The peak value of BOD and the dose required to reach the peak were almost proportional to the initial concentration, and pH did not much affect the change of BOD. The low dose rate did not bring about much merit. (Kako, I.)