Yangzhou Liuwei WWTP, Phase II expansion 10×104 m3/d, successfully used Bioprocess Intelligence Optimization and Dynamic Control System (BIOS II), achieved energy saving 23.3% in 2011, reduced electricity costs more than ￥1,960,000, and accessed to Jiangsu “Eleventh Five” advanced emission reeducation company and “Jiangsu science and technology progress award” three awards. Phase III expansion 5 ×104 m3/d, used BIOS II again in 2015. BIOS II of phase III started up in April, and intergraded with upgraded BIOS II of phase II.
l System design and control process
I, Bioprocess Intelligence Optimization and Dynamic Control System (BIOS II) combined feed-forward control and feed-back control.
Feed-forward control means using data of instruments in front of bioreactor
Feed-back control means also monitoring effluent NH4-N&NO3-N
II, BIOS II is a preface system based on unique influent components of every WWTP.
Before BIOS II staring up, Biochem engineers will use ABAM equipment to analyze influent components on site, and test OUR/NR/DNR. All these data will be confirmed as initial parameters of BIOS II.
In system operation control, BIOS II always calculates real time OUR/NR/DNR through DO and air flow data. All these data have been stored in complete internal database and used to revise initial data.
III, BIOS II used ASM2D model instead of traditional PID control.
BIOS II calculates air flow set point and air control valves position through real time data to trace DO without PID compensation.
Left figure is valve curve under BIOS II control, 7 moves in 20 min
Right figure is valve curve under PID control, 26 moves in 20 min
BIOS II can increase lives of electric actuators 6 times than PID control.
IV, BIOS II combines the control of air blowers and electric valves to save aeration energy.
BIOS II uses unique MOV logic to ensure some valve keep on bigger position and reduce pressure of pipe system. This causes air blowers can work with air flow control in less back pressure.
V, BIOS II reduces aeration energy and provide better condition for nitrification and de-nitrification react.
BIOS II control DO according to influent NH4-N concentration and ensure low DO level in IRQ witch benefit for nitrification react.
Curves under BIOS II control： air blowers changed total air flow with influent NH4-N。
1：High air flow meets high influent NH4-N to keep effluent discharge match permit；
2：Low air flow meets low influent NH4-N to reduce aeration energy.
l Equipments
Equipment | Quantity | Specification |
BIOS II control box | Phase II：1 set Phase III：1 set | Biochem. 4 PLC panel，2 IPC，1 HMI DO control , IRQ control, air blower total air flow control, valve position control |
Air blower | Phase II：4 sets Phase III：2 sets | ABS maglev blower（4500m3/H-11000m3/H） ABS maglev blower（4500m3/H-11000m3/H） |
Air control valve / actuator | Phase II：6 sets Phase III：6 sets | VAG /Auma VAG /Auma |
Air flow meter | 6+2 sets | FOX |
diffuser | Switch zone Ox zone | corundum corundum |
DO analyzer | Phase II：6 sets | Biochem |
DO/MLSS analyzer | Phase II：2 sets | Biochem |
NH4-N analyzer | Phase II：2 sets | Biochem |
NH4-N/NO3-N analyzer | Phase II：2 sets | Biochem |
Phase III BIOS II main menu：Green pipe Influent pipe , Red pipe IRQ pipe, Gray pipe RAS pipe, Arrow flow direction.
Phase II：6 air control valves/air flow meters installed in each pipe to control air flow
1 air flow meter installed in main pipe to control total air flow
NH4-N&NO3-N analyzer install in front/end of bio-reactor
DO analyzer installed in each control zone
DO analyzer installed in the end to monitoring returning liquild
BIOS II calculates best DO set point according the data form NH4-N analyzer installed in anoic zone
BIOS II calculates best DO set point according influent flow data.
After BIOS II started up in Feb, 2011 annual mean DO control is 90.9% in the range of ±20%.
DO data under BIOS II control compared with manual control, reduced aeration energy at 23.3%.