Oxidation Ponds Flashcards
What are WSP?
Waste Stabilisation Ponds.
Why are WSPs good?
Use solar and wind energy.
Excellent disinfection if short circuiting is minimised.
New technologies to improve effluent quality.
Are WSP old or new technologies?
They are not old.
Is it expensive to upgrade WSP to higher performance?
No
Are WSP used worldwide?
Yes
The anaerobic or settlement zones for high solid wastes have to be greater than how many meters?
2m
Why is it essential to mix in calm conditions?
To bring algae to the surface for sunlight.
Why is it good to have multiple ponds in series?
For efficiency.
How is short circuiting reduced?
Position inlet and outlets with flow against prevailing wind.
Flat floors.
When are stub baffles effective?
In smaller ponds.
Not effective in larger 40 ha ponds.
What shape should primary ponds be and why?
Nearly square to allow complete mixing and encourage algae growth
What do we design ponds to? (loading terms)
84 kgBOD/ha.d or 1200 persons/ha.
How many primary ponds should be in parallel and why?
2 or 3.
Flexible loading if one pond is upset.
What id the secondary pond size?
30% of the first.
Maturation ponds can be elongated to approximate plug flow.
What are the variations of WSP for improvement?
Anaerobic/aerobic Facultative ponds Multi maturation cells in series AIPS High rate add-ons (eg PETRO)
How to improve the filtration?
Rock filters or trickling filters for ammonia reduction.
What are some potential add ons?
- UV disinfection
- Chemical dosing
- Dissolved air flotation
- Sand Filtration
- Membrane filtration
What are reduced by ponds in series?
Faecal coliform, enterococci and e.coli.
What is the concentration typically achieved without UV by 4 ponds in series?
less that 1000/100 ml
Why are ponds good at removing pathogens?
Sunlight DO Temp Retention Time pH Predation Settlement
Is disolved oxygen important for sunlight inactivation?
Yes, needs to be more that 4 g/m^3
Why have deeper ponds in terms of sludge?
1.5 - 2m. so the overlying liquid controls the odor.
Is it better to have a deeper pit near the inlet?
Yes, it stores incoming solids and creates ideal conditions for anaerobic digestion.
How ofter does sludge removal take place?
Every 15 to 30 years.
Why have an extra primary pond in terms of sludge?
So you can drain one to remove sludge.
How well can sludge be air dried?
50-60% DS (what does that mean lol)
Other than drying, what are other methods it can be removed?
- Slurry using suction cutter dredge or pumps on pontoon.
How is sludge dewatered?
Portable belt press or centrifuge with polymer dosing.
Where can sludge be disposed?
Landfill or forests depending on content.
