By Colin Kellaher

Waste Management Inc. Wednesday said it reached a revised agreement to buy competitor Advanced Disposal Services Inc. that includes the sale of a group of assets to GFL Environmental Inc. to assuage antitrust concerns.

Houston-based Waste Management said it will now pay $30.30 a share in cash for Advanced Disposal, down from the $33.15 a share it agreed to pay when the waste-disposal companies struck their deal last year.

The revised transaction represents a total enterprise value of $4.6 billion, including roughly $1.8 billion of Advanced Disposal debt, down from about $4.9 billion.

Waste Management said the two companies have agreed to sell a combination of assets representing about $345 million in revenue to Canada's GFL for $835 million. Waste Management said it expects the sale will address substantially all of the divestitures the U.S. Department of Justice will require for approval of the Advanced Disposal deal.

Waste Management said it expects to complete the Advanced Disposal acquisition by the end of the third quarter.

Shares of Advanced Disposal, which closed Tuesday at $31.16, fell 3.5% to $30.07 in premarket trading Wednesday.

Write to Colin Kellaher at colin.kellaher@wsj.com