SEWAGE TREATMENT PLANTS
With the effort to reduce environmental impacts of sewage discharge into the surrounding areas, Lankayan Island and Billean Island are equipped with their unique sewage treatment plants to treat waste water collected from toilets, bathrooms, and kitchens before it is discharged into the vegetation area, sea, or to be used for watering potted plants. Each sewage treatment plant is integrated from three different treatment systems, which include:
- Primary Treatment System,
- Hydroponic Treatment System (HTS) (secondary treatment system), and
- Ozone Disinfection System (tertiary treatment system).
I. Primary Treatment System
Primary treatment system is consisting of raw sewage sump, balance tanks, Moving Bed Biofilm Reactor (MBBR) tanks and sludge drying beds. The primary feature of this treatment system lies on the MBBR system, which utilises microorganisms to break raw sewage down into minerals.
Plastic moving media are applied in MBBR system to provide protected surface area for the microorganisms to grow, and the aeration system just above the base of the MBBR tanks is set to supply oxygen for decomposition processes of organic wastes, as well as for respiration processes by the microorganisms.
Another feature of Primary Treatment System is the settlement tank. Tilted tube clarifier in this tank aids in rapid settlement of suspended solids into the base of the tank by gravity. The top layer of the water will flow to HTS tanks, whereas the bottom layer will be channeled to sludge drying beds.
In sludge drying beds, sludge is dried through evaporation and filtration processes. This dried sludge is used as fertilizer for potted plants.
II. Hydroponic Treatment System (HTS)
HTS operates by eliminating or reducing nutrient in sewage through nutrient absorption by hydroponic plants roots.
This system is highly oxygenated to actively aid in ensuring deep plant root penetration, which successively helps in nutrient uptake and antibacterial treatment. The additional input of oxygen converts ammonia into nitrogen which can be released to atmosphere.
III. Ozone Disinfectant
In the final treatment process, sewage is fed with ozone to kill bacteria and viruses before it is released into the open area. Generated ozone is supplied into a down-flow contact chamber containing sewage, where ozone is diffused into fine bubbles at the bottom of the contact chamber.
Apart from the down-flow contact chamber, the ozone is also fed into ozonation tanks and effluent tank to enhance the disinfection process.