Coleraine based waste and environmental specialist ATG Group has secured a £3.5m contract in the Republic of Ireland.
The contract, which was secured with The Department of Agriculture, Food and the Marine to treat and dispose of contaminated dredge material, is now under way.
It follows a major £1m investment in the business and the creation of 14 jobs.
Making the announcement, Dr Mark McKinney, managing director of ATG Group, said: "To help increase our export sales, we are investing £1m in our business and are recruiting new staff.
"This has meant we have been able to win this major contract in partnership with ABCO Marine in Killybegs Harbour."
To date, ATG has processed and treated 4,500 tonnes of material per week and has stabilised 16,200 tonnes.
"In the past three years, our sales have more than quadrupled and our reputation in the waste recycling sector is rapidly growing.
"Working with Invest NI over the years has proved invaluable to this success.
"Its support for our marketing activities, technical advice and 14 new staff has enabled our business to move from a focus on the local market, to making great inroads in GB and RoI.
"Our next steps will be to expand into new markets, particularly Europe and Africa."
ATG Group, which is based at Loughanhill Industrial Estate, provides specialist services in environmental remediation, waste management and invasive species treatment.
The company has extensive expertise and experience in a broad range of environmental and waste solutions, especially in cleaning up brownfield sites that have been invaded by plants such as Japanese knotweed, as well as polluted by complex contaminants including fuel oils and heavy metals.
The company has warned that invasive species such as Japanese knotweed could cost Northern Ireland £46.5m a year. The weed - branded an invasive alien species by Europe - can grow to eight feet or more in a single season and is capable of causing serious structural damage to buildings.
It is an offence to plant or cause Japanese knotweed to grow in the wild in Northern Ireland.
The Ministry of Defence was forced to spend more than £3m decontaminating the former Fort George army base in Derry, which had been polluted with heavy oils and diesel, as well as small amounts of heavy metals.
Invest NI has offered the company £98,700 of support to create 14 jobs, 10 of which are in place, and to undertake a range of marketing activities.
The company has also availed of technical assistance to develop and trial innovative new treatment processes.
Des Gartland, Invest NI's North West regional manager said: "We are delighted to be supporting ATG Group as it endeavours to rapidly grow its exports.
"Our support has allowed the company greater flexibility to bid for bigger contracts, including this recent contract at Killybegs Harbour."