Duong Nhat accompanied with Dong Hai Joint Stock Company of Ben Tre (DOHACO) in the project “Wastewater treatment plant of Giao Long Paper Mill”. Giao Long Paper Mill, which is one of the largest paper processing factory in Ben Tre province, is ranked in TOP 10 of Vietnam Paper Industry with total production capacity is 300.000 tons paper/ year.
(Wastewater Treatment Plant of Giao Long Paper Mill)
The factory has been officially put into productive operation and the wastewater treatment plant (WWTP) operated stably. Duong Nhat would like to share some experiences in handling problems that could happen in the WWTP of paper mill.
Solutions and remedies to handle problems in the WWTP of DOHACO during start-up period are described as following:
1. Process of discharging waste from Paper Forming stage is uncontrollable because the balance process for production line is still unstable (Max discharge flow-rate is 1.100 – 1.200 m3/hr), which overflow the ditch and receiving system.
• Solution:
+ There are always backup pumps in the system;
+ The emergency water storage tank must be installed in the system to receive this source of wastewater.
• Remedies:
+ Install backup pump additionally;
+ Control discharge process and prepare all plans to be ready to handle.
2. Garbage and sand separation systems in production line meet problem, causing garbage and sand entered into the system without control.
• Solution:
+ Design the inlet coarse screen with the safe overloaded coefficient;
+ There are always backup coarse screens;
+ Must have the complete sand trap system before the receive system.
3. Input wastewater has detergent, biocide, high surface-active substances that affect the process of microbiological activities, resulting in unstable effluent quality.
• Solution:
+ Must have specific storage tank for detergent wastewater installed with complete aeration equipment;
Water retention time in tank is from 10 – 15 days. After 10-15 days, pumping slowly under flow-rate control to treat along with production wastewater. All of microbiological activity parameters are monitored closely during the pumping process.
• Remedies for the biological system affected by the source of water which has detergent and biocide substances:
+ Stop loading, then run internal circulation for biological tanks.
+ Circulate with dilution to reduce toxins in biological tanks.
+ Add anaerobic and aerobic probiotics to restore sludge biomass and increase microbiological density for biological sludge.
4. The wastewater temperature discharged from the factory to the collection system is high, as average 42-45oC that affect bacteria in biological treatment tanks.
• Solution:
+ Must have the cooling system in order to ensure temperature lower than 37oC before entering the biological system.
+ Install online temperature monitoring equipment inside the equalization and biological tank.
• Remedies for microbiological system affected by temperature:
+ Stop loading to monitor wastewater temperature, then start to load from low to high when the temperature is lower than 37 0C;
+ Circulate internally treated wastewater which has low temperature to reduce temperature of inlet wastewater;
+ Add anaerobic and aerobic probiotics to stabilize the system.
5. Pollution concentrations exceed the design threshold. COD, TSS are higher than the design threshold, resulting in overloaded system.
• Solution:
+ Balance the process of circulating water in the production system;
+ Regularly control water quality in the pulp reservoir.
• Remedies for overloaded system:
+ Reduce inlet flow-rate to ensure the stable condition for the system.
+ Add anaerobic and aerobic probiotics to stabilize the system.
+ Control inlet flow-rate to ensure that the inlet loading does not exceed the design threshold;
+ Add new water or replace water in the pulp reservoir in order to get contaminated components back to the design level.
PICTURE TAKEN WHEN PROBLEM HAPPENED
(Production line has problem that discharged wastewater and trash make the system overloaded)
(The WWTP must run beyond the design load to treat wastewater for the factory)
(Wastewater from cleaning process of the factory was pumped improperly to the biological system)
(Inlet wastewater contains detergent substance and foam that affect the microflora negatively)
(High temperature have negative impact on the bacteria. The microbiological system suffered from heat shock)
DUONG NHAT – ALWAYS CARRY BETTER THAN COMMIMENT
