Rate hike filings come as the state’s major water utilities seek merger. CHICAGO — Customers across Illinois could be facing higher water and sewage bills as the state’s largest private water utilities seek rate increases and permission to merge. Illinois American Water, the state’s largest private water utility, is seeking a $142 million rate increase, which would raise typical water costs for its 357,000 residential customers by around $14 per month. Typical wastewater customers would see an additional increase of around $28 per month. Aqua Illinois, the second-largest private water utility serving over 90,000 customers in the state, has asked...