A flowery fragrance fills the air at the Drainage Services Department's Siu Ho Wan Sewage Treatment Works, hardly the smell expected at a sewage plant.
But at this facility, which has the capacity to treat 180,000 cubic metres of sewage a day, the stench of wastewater is washed out by the fragrance produced by a teeming ecosystem made up of 50 plant species.
Trees and shrubs are housed at the treatment works' nursery where the department's landscape architects cultivate native plant species.
Responsible for greening and landscape planning, design and management, the landscapists visit the nursery twice a week and have found a number of plants help enrich the biodiversity of the facility through their ability to attract insects and purify water.
When Landscape Architect Stanley Hoi steps into the nursery, he is greeted by bees and butterflies.
Many plant species depend on these insects to disperse pollen, a key ingredient in their reproduction.
"Reevesia thyrsoidea is a native tree. The flower is very showy and the fragrance can attract many butterflies and bees," Mr Hoi said.
Another plant in the nursery, Garcinia oblongifolia, produces yellow fruit, while Celosia argentea has uniquely shaped flowers and Coix lacryma-jobi can filter nitrogen and phosphorus from water.
Mr Hoi said all four species are well suited for the sewage facility, while Coix lacryma-jobi can also be planted on riversides.
More than 15 green roofs have been installed by the Drainage Services Department at various sewage treatment works in recent years in an effort to beautify the facilities.
Landscape Architect Sandy Tong said greening features in both new and old sewage facilities is a good thing for the community.
She joined the department two years ago and said greening features at the Sha Tin Sewage Treatment Works, built in 1982, have helped the district's appearance.
"(For) the landscape works in the Sha Tin Sewage Treatment Works, there are three aspects.
"The first one is at-grade planting, the second one is roof greening and the third one is vertical greening, to enhance the biodiversity of the site and also the surrounding environment.
"(It) provide(s) a better visual impression to the neighbourhood and also the staff within the facility."
The Drainage Services Department will hold open days at Sha Tin Sewage Treatment Works on January 27 and 28.
The public can learn about the department's work on flood prevention, sewage treatment and greening works through a variety of entertainment and educational programmes.