The disposal of sewage is one of the most important problems that confront the municipal and sanitary engineer to-day.

The study of this subject dates back to 1844 when the Healths of Towns Commission of London made the report which first showed the real course of the rapid increase in the death rate of the larger cities. In this country practically nothing was done until 1872 when the Massachusetts Legislature instructed the State Board of Health to investigate and report on the subjects of sewerage, sewage disposal, and the pollution of streams, and to-day Massachusetts leads in the investigation of the best methods of sewage disposal.

Six different methods for the treatment of sewage are now in use. These methods are used separately or in combination, the choice depending upon local conditions and the amount of purification required:—

These methods are:

1—

Dilution.

2—

Irrigation.

3—

Intermittent Downward Filtration.

4—

Chemical Precipitation.

5—

Septic Tank.

6—

Contact Bed.

The purpose of this thesis is to investigate each method and make a comparison along the following lines:

1—

Purification.

2—

Capacity.

3—

Applicability.

4—

Cost.