Page 15 - Australian Pork Newspaper
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Aerator conversion nets lower energy costs, eliminates surcharges and enhances lagoon performance
A FOOD processing facility discharges the plant’s effluent into a wastewater treatment lagoon system for the reduction of BOD, phos- phorus, ammonia and TSS prior to discharging to the local wastewater treatment plant.
The facility discharges about 285,000kl/day with BODs about 350mg/l.
The lagoon is very large [195m x 75m] with an op- erating depth of 2.7m to 3m with sufficient reten- tion time for biological processes.
A hanging curtain baffle provides an area of qui- escence on the discharge side to reduce TSS and divides the lagoon.
The lagoon was origi- nally equipped with five 11kW high-speed float- ing impeller-type aerators and three 15kW draft tube surface aerators for a total of 100kW of connected power.
While these aerators were able to mix and re- circulate liquids in the lagoon, they were not capable of adequately in- fluencing the biological treatment for organic re- ductions to include nitri- fication.
Additionally, there was an increasing sludge accu- mulation of almost 1m of varying thickness (great- er than 3 percent solids) throughout the lagoon.
In this configuration, the facility was not able to
meet their discharge per- mit limits issued.
As a result of not com- plying with their dis- charge permit, the facility was being charged.
They began to look for alternative treatment solu- tions to bring the facility into compliance, as sur- charges were approaching $70,000 a year.
Due to the depth of the sludge (2m below the sur- face air/liquid interface) the existing units and the floating surface aerators were not effectively resus- pending the sludge for di- gestion, but rather allowed the sludge to accumulate on the bottom.
The bottom 560mm of sludge was >3 percent sol- ids while the next 300mm was a slurry varying be- tween 1 to 3 percent sol- ids.
The sludge was occu- pying 25 percent of the lagoon’s total volume.
Hydro Innovations’ venturi aeration repre- sentative looked at the dissolved oxygen require- ments and determined that four medium-sized venturi aerators would be required for this lagoon, since the BOD loadings were not significantly high.
The plant proceeded with the recommendation. Energy savings
In the first year, two venturi aerators brought the facility into compli- ance.
Phase two (adding a fur- ther two) was then imple- mented.
This involved the addi- tion of two Model VA- 600 venturi aerators and two Gorman-Rupp Model 84A52-B direct-coupled pumps with 15kW TEFC motors.
With all four venturi aerators operating at the same time, the eight sur- face aerators could be dis- continued.
Therefore, there were energy savings due to less operating power (52kW v 100kW).
This is a ‘saving’ of 48kW x 24 hours, which equals 1152kW per day.
At 10c/kWh, this is a $115.20 saving per day, $3404 a month or $42,048 per annum.
With all four venturi aerator systems in opera- tion, the facility complies their discharge permit.
BOD levels average 35, TSS 70, ammonia <1mg/l, phosphorus <3mg/l, ni- trate <1mg/l.
Because the venturi aer- ator is consistently strip- ping the carbon dioxide generated by the aerobic bacteria, the pH is buff- ered non-chemically.
The facility’s discharge pH averages 8.0 without the addition of alkalinity.
The sludge blanket has been reduced to almost zero on the aerobically treated side of the baf- fle, while in the quiescent zone there is only an aver- age of 100mm of sludge with <3 percent solids.
Because of the unique suction piping and dis- charge configuration, there is better mixing and equalisation of the con- tents of the lagoon.
This installation also has a subsurface discharge of the Venturi Aerator treat- ed liquids, which allows the entrained ‘macro-bub- bles’ to rise like a diffuser, but unlike a diffuser there is a high Reynolds num- ber associated with the high degree of turbulence
in the discharge piping, which increases oxygen transfer.
By pushing out the ‘en- trained’ micro-bubbles horizontally, they travel a greater distance (up to 30m) than the rise of a bub- ble from a diffuser (in this case it would be only 2.7m).
This subsurface dis- charge is ideal where there is not a requirement for CO2 stripping to raise pH.
For more information, contact Hydro Innova- tions on 02 9898 1800 or sales@hydroinnovations.
Potential FMD vaccine components trialled in pigs
NEW research dem- onstrates that certain B-cell proteins pro- vide pigs with long- lasting immunity to food and mouth dis- ease.
According to a re- cently published ab- stract in Transbound- ary and Emerging Diseases, research- ers have been able to isolate the synthetic protein B2T(mal) and demonstrate its ability to elicit B- and T-cell specific immune re-
sponses in pigs.
In trials, two doses
of B2T(mal) elicited an immune response that gave pigs relia- ble protection against type O foot and mouth disease virus chal- lenges.
After injection, the pigs retained immu- nity to FMDV chal- lenges for up to 136 days (19-20 weeks).
Read the origi- nal abstract at onlinelibrary.wiley. com/doi/abs/10.1111/ tbed.13497
Australian Pork Newspaper, February 2020 – Page 15

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