With tears in their eyes, mothers of children who died in Brazil’s worst environmental disaster – the 2015 Mariana dam collapse – demanded justice for their loved ones as submissions in their London lawsuit came to an end.

Nineteen people were killed when the Mariana dam in south-eastern Brazil collapsed and unleashed a wave of toxic sludge, leaving thousands homeless, flooding forests and polluting the Doce River.

The dam was owned by Samarco, a joint venture between Vale and Anglo-Australian BHP, the world’s biggest miner by market value.

“It was the day that destroyed my life … the day that took away my son,” Gelvana Silva, 37, said outside the high court in London. She lost her seven-year-old son, Thiago, in the flood.

More than 600,000 Brazilians, 46 local governments and about 2,000 businesses are suing BHP over the disaster in a lawsuit worth up to £36bn.

The lawsuit, one of the largest in English legal history, began in October and ended on Thursday with closing submissions.

“I will produce a judgment as soon as I can,” said the judge, Finola O’Farrell, as she announced the end of the trial.

Pamela Fernandes, 31, lost her five-year-old daughter, Manu. “The memories of Manu are always with me … it’s very difficult.“

Fernandes, who like Silva wore a T-shirt bearing her late child’s picture, said: “I want justice so that I can be at peace, so that my daughter can be at peace.”

BHP said the London lawsuit duplicates legal proceedings and reparation and repair programmes in Brazil and should be thrown out. It also said nearly $8bn (£6.2bn) has been paid to those affected through the Renova Foundation, with about $1.7bn going to claimants involved in the English case.

BHP argues it did not own or operate the dam, which held mining waste known as tailings. It said a Brazilian subsidiary of its Australian holding company was a 50% shareholder in Samarco, which operated independently.

The miner also said it had no knowledge the dam’s stability was compromised before it collapsed.

The Brazilian government signed a compensation deal with BHP, Vale and Samarco in October but Tom Goodhead, the chief executive of Pogust Goodhead, has said victims of the disaster were not involved.

Goodhead, representing the claimants, said on Thursday the trial was about accountability.

“If the company is [found liable], it will be the biggest victory for us … it would have been worth waiting 10 years,” Silva added.