The “Yuen Long Water Purification Facility”, which is under reconstruction and is expected to be put into operation in 2027, introduces “aerobic wastewater treatment technology” for the first time, using “aerobic granule” sludge beads to cleaning, one-stop sewage treatment, reducing the space required for the previous treatment, save electricity required to adjust the treatment environment, cooperate with the improvement of inlet and outlet water design and technology of co-anaerobic energy generation of solar energy and sludge. The drainage services department described, “Save more, produce more” can make the plant “energy neutral”, becoming the first self-sufficient wastewater plant in Hong Kong for power generation.
Located in Yuen Long Industrial Zone, Yuen Long Sewage Treatment Plant, covering an area of 8.6 hectares, has been in operation for more than 30 years. The original site will be reconstructed at the end of 2020, and the level of the wastewater treatment will be upgraded from the second level to the third level, which can reduce the amount of purified water by 50% The residual organic matter also increased the wastewater treatment capacity from 70,000 cubic meters per day to 100,000 meters cubes, becoming the “Yuen Long Water Purification Facility” and applying the “aerobic granular sludge technology” for the first time.
Chen Yunyin, engineer of the drainage services department, said that traditional sewage treatment plants need to separate the aerobic zone, anoxic zone and anaerobic zone. The microorganisms in the oxygen zone will remove the ammonia that poisons the fish, which requires a large space, and also uses energy to start the air pump for a long time to maintain a suitable living environment for microorganisms.
Granules for 3 concentrations of dissolved oxygen
The new technology provides only three concentrations of dissolved oxygen through aerobic granular sludge beads with a diameter of only 0.2-0.4mm “Gas” and 3-step “rapid sedimentation”, microbial retention and water purification, removing at the same time organic matter, ammonia, nitrogen, phosphorus and other pollutants.
Chen Yunyin said that aerobic granular mud beads are conducive to oxygen penetration, can control the amount of oxygen more accurately, reduce the energy consumption of mechanical equipment such as agitators and circulating pumps during the aeration (aeration) stage and their volume is relatively small. In the past, the sludge grains were large and the sedimentation rate was higher, which could process the wastewater faster and reduce the land demand. Aerobic granular sludge technology is expected to reduce electricity consumption by about 20% compared to the past.
The Department of Drainage Services has also installed a pumping station at the mouth of the factory building, which will only be activated when the river is in high tide, and hydraulic pressure will be applied to discharge the water, reducing the height of pumping untreated wastewater enter the sewage treatment plant and save energy. Chen Yunyin pointed out that the water pump only needs to be started once a year. Compared with not adding a water outlet pump room at the water outlet point, the factory can save about 16% of the electricity consumption than in the past.
At the same time, co-anaerobic technology is installed in the plant, which uses microorganisms in an oxygen-deficient environment to digest sludge formed during the wastewater treatment process and generate biogas for energy production. The Department of Drainage Services expects to produce approximately 3.5 million kilowatt-hours of electricity per year in the initial phase of operation, sufficient to meet approximately 30% of the plant’s electricity needs, in addition receiving approximately 125 tons of anaerobic digestion of sludge from other treatment plants when utilization is not at its peak and is estimated to generate an additional 8.2 million kilowatt-hours of electricity per year, enough to meet the remaining 50% of the plant’s electricity demand A total of 11.7 million kilowatt-hours of electricity is equivalent to the annual electricity consumption of approximately 3,545 three-person households.
5,000 photovoltaic panels on top of government facilities
The water purification plant is also equipped with a solar power generation system consisting of more than 5,000 solar photovoltaic panels, which will be the largest solar power generation plant in Hong Kong government facilities. annual energy will reach 2.3 million kilowatt-hours, which is enough for about 700 three-person households to use throughout the year.
It’s just that after the reconstruction, the cost of wastewater treatment at the facility went from 2.1 yuan per cubic meter to 6.1 yuan. Chen Yunyin explained that since the plant was upgraded to a third level, filtration and ultraviolet light disinfection procedures have been added; While the cost of wastewater treatment is difficult to compare, Aerobic Sludge Beads are still patented and the cost is “cheaper” than before. However, mud beads can be used continuously and will not be worn out until many years later.
