At least four groups register for Rio sanitation auction, source says

* Auction vital boost for state’s finances

* Could be biggest in Brazil this year

RIO DE JANEIRO, April 28 (Reuters) - At least four potential bidders have registered for the auction of concessions managed by Rio de Janeiro state water and sewage utility Cedae, a source with direct knowledge of the matter told Reuters on Wednesday.

The auction, expected to conclude on Friday, could be one of the largest privatizations in Brazil this year and is considered a key step in shoring up Rio de Janeiro state’s shaky finances.

The four concessions are being sold separately with a minimum bid for all four set at 10.6 billion reais ($1.94 billion). The winners are set to be announced on Friday.

Sanitation company Igua Saneamento SA, water and sewage firm Aegea, a consortium led by Equatorial Energia SA and a consortium involving sanitation company BRK Ambiental have all registered, said the source, who requested anonymity to discuss confidential matters.

Aegea confirmed to Reuters that it had submitted a bid. Equatorial said it had submitted an offer in a Wednesday morning securities filing. BRK declined to comment. Igua Saneamento did not immediately respond to a request for comment.

Signing up for the auctions makes the groups eligible to bid but does not necessarily mean they ultimately did so.

State development bank BNDES, which is overseeing the auction, did not say which companies had signed up, but Guilherme Albuquerque, the head of the bank’s public-private partnership division said: “The auction has the interest of the market... It’s going to be eventful, and there will be competition.”

BRK is controlled by Canada’s Brookfield Asset Management Inc.

Brazilian investment firm Itausa SA announced on Tuesday it would invest 1.3 billion reais in Aegea.

In late March, Canadian pension fund CPPIB acquired a 45% stake in Igua Saneamento for 1.18 billion reais. ($1 = 5.45 reais) (Reporting by Rodrigo Viga Gaier; Additional reporting by Gram Slattery in Rio de Janeiro and Aluísio Alves in Sao Paulo; Writing by Gram Slattery; editing by Philippa Fletcher)