The former superintendent of Plainville’s sewer plant has been sentenced to four years in prison after being convicted on corruption and other charges. Kenneth Michelson was sentenced in New Britain Superior Court on Monday.

He had pleaded guilty under the Alford Doctrine to 20 felony charges including larceny, tampering with evidence and other crimes. A defendant who invokes the doctrine does not admit guilt, but concedes the prosecution has enough evidence to convict.