Reverse osmosis units were overhauled.

After almost three-and-a-half years of delays, litigation and controversy, the nation’s largest desalination plant has passed a final round of testing and become part of the Tampa Bay Water system.

The Tampa Bay Seawater Desalination Plant at Apollo Beach successfully completed a 14-day acceptance test. The plant produced 25 million gallons per day of fresh water for a week, then 28 mgd a week later, said Ken Herd, TBW director of operations and facilities.

The utility presented test results to the TBW Board of Directors on Dec. 17, officially completing the project’s construction phase.

A joint venture of American Water and Pridesa America Corp. was hired in 2004 as the remediation contractor. With the successful test, the team now can collect the final $3 million on its $29-million contract.

The plant failed initial tests in 2003. The utility twice brought in new design teams, filed several lawsuits and ordered extensive reworking of the pretreatment scheme. Engineers installed 18 precoat diatomaceous earth filters and carried out a major retooling of the existing sand-filter process, converting 16 dual-stage sand filters to 32 single-stage sand filters.

The plant’s cost rose from $110 million to $158 million. “The community’s investment to overhaul this plant has paid off,” said Jerry L. Maxwell, the utility’s general manager.

� “We’ll see the benefit in a more diversified, drought-resistant water supply network.” The plant can supply 10% of the region’s drinking water.