Section 17. The department of environmental protection, in this section called the department, shall consult with and advise the officers of towns and persons having or about to have systems of water supply, drainage or sewerage as to the most appropriate source of water supply and the best method of assuring its purity, or as to the best method of disposing of their drainage or sewage with reference to the existing and future needs of other towns or persons which may be affected thereby. It shall also consult with and advise persons engaged or intending to engage in any manufacturing or other business whose drainage or sewage may tend to pollute any inland water as to the best method of preventing such pollution, and it may conduct experiments to determine the best methods of the purification or disposal of drainage or sewage. Towns, districts and persons shall submit to said department for its advice and approval their proposed system of water supply or of the disposal of drainage or sewage, and no such system shall be established without such approval. All petitions to the general court for authority to introduce a system of water supply, drainage or sewerage shall be accompanied by a copy of the recommendation, advice and approval of said department thereon. The department may after a public hearing require a town, person, district or water company to make such improvements relative to any existing treatment, works or system of water supply as in its judgment may be necessary for the protection of public health. In this section the term ''drainage'' means rainfall, surface and subsoil water only, and ''sewage'' means domestic and manufacturing filth and refuse.