A field study of a household package treatment plant

The field operation of an individual household aerobic treatment plant was investigated. The treatment plant study was paralleled by a literature survey of current disposal system practices. It was found that the Cromaglass type CA5-D aerobic wastewater treatment system produced, under current installation and operation practices, an average effluent of 85 mg/l BOD and 79 mg/l SS. Under similar circumstances, the type CA5-E plant produced an average effluent quality of 67 mg/l BOD and 56 mg/l SS. As neither type of plant operated with a VSS concentration of greater than 150 mg/l, the treatment process cannot be described as a modification of the activated sludge system. The literature indicates that the mechanisms and processes occurring in wastewater disposal systems are inadequately understood. As a consequence, no adequate test has yet been developed which is capable of relating measurable soil conditions to suitability for a disposal field. However, several authors have suggested that average effluent BOD's of approximately 40 mg/l will be required to permit a significant increase above current absorption field hydraulic loadings. Under present conditions of installation, service, operation, and effluent quality, it is probable that significant relaxation of design criteria for in situ and imported fill disposal fields cannot be permitted for the Cromaglass treatment systems.Applied Science, Faculty ofCivil Engineering, Department ofGraduat