The proportion of firms failing to comply properly with permits issued by the Environment Agency fell from 4.1% in 2014 to 3.2% in 2015.
The percentage of serious incidents at permitted sites declined by 32% between 2014 and 2015, the regulator said. However, performance varied considerably across the 13 sectors it regulated.
The biggest decline in serious pollution in 2015 was in the landfill sector, which caused 13 incidents compared with 36 in the previous year, according to the data. Cases of minor pollution fell from 259 in 2014 to 195 in 2015. The agency cited the work it had undertaken with the sector for the improvement.
Performance in other parts of the waste industry changed little between 2014 and 2015. There were 36 serious pollution incidents at biowaste treatment facilities in 2014 and 35 in 2015. Some 60% of 704 sites operated by the sector were rated A for site compliance, while 20 were persistently classified as poor performers.
In metals recycling, 57% of 2,592 regulated sites were found to be top performers, with 26 facilities rated as persistently poor. Serious pollution incidents rose from 13 in 2014 to 16 in 2015. Ninety-one of 4,403 non-hazardous waste sites were rated as persistent poor performers. There were 40 serious pollution incidents in 2015, down from 48 in 2014. There were 491 serious permit breaches and eight sites had permits removed.
The cement, lime and minerals sector had the best-performing sites, with 87% of 229 facilities achieving an A rating, and 11% a B. There were no sites with a compliance rating of E or F. Eighty per cent of combustion power sites were awarded the highest compliance rating. It was the only sector with all sites achieving one of the top three rankings. Some 71% of 449 sites in the chemicals sector achieved an A rating, and 21% a B.