Oxidation Ponds

Question 1

What are WSP?

Answer 1

Waste Stabilisation Ponds.

Question 2

Why are WSPs good?

Answer 2

Use solar and wind energy.
Excellent disinfection if short circuiting is minimised.
New technologies to improve effluent quality.

Question 3

Are WSP old or new technologies?

Answer 3

They are not old.

Question 4

Is it expensive to upgrade WSP to higher performance?

Answer 4

No

Question 5

Are WSP used worldwide?

Answer 5

Yes

Question 6

The anaerobic or settlement zones for high solid wastes have to be greater than how many meters?

Answer 6

2m

Question 7

Why is it essential to mix in calm conditions?

Answer 7

To bring algae to the surface for sunlight.

Question 8

Why is it good to have multiple ponds in series?

Answer 8

For efficiency.

Question 9

How is short circuiting reduced?

Answer 9

Position inlet and outlets with flow against prevailing wind.
Flat floors.

Question 10

When are stub baffles effective?

Answer 10

In smaller ponds.

Not effective in larger 40 ha ponds.

Question 11

What shape should primary ponds be and why?

Answer 11

Nearly square to allow complete mixing and encourage algae growth

Question 12

What do we design ponds to? (loading terms)

Answer 12

84 kgBOD/ha.d or 1200 persons/ha.

Question 13

How many primary ponds should be in parallel and why?

Answer 13

2 or 3.

Flexible loading if one pond is upset.

Question 14

What id the secondary pond size?

Answer 14

30% of the first.

Maturation ponds can be elongated to approximate plug flow.

Question 15

What are the variations of WSP for improvement?

Answer 15

Anaerobic/aerobic
Facultative ponds
Multi maturation cells in series
AIPS
High rate add-ons (eg PETRO)

Question 16

How to improve the filtration?

Answer 16

Rock filters or trickling filters for ammonia reduction.

Question 17

What are some potential add ons?

Answer 17

• UV disinfection
• Chemical dosing
• Dissolved air flotation
• Sand Filtration
• Membrane filtration

Question 18

What are reduced by ponds in series?

Answer 18

Faecal coliform, enterococci and e.coli.

Question 19

What is the concentration typically achieved without UV by 4 ponds in series?

Answer 19

less that 1000/100 ml

Question 20

Why are ponds good at removing pathogens?

Answer 20

Sunlight
DO
Temp
Retention Time
pH
Predation
Settlement

Question 21

Is disolved oxygen important for sunlight inactivation?

Answer 21

Yes, needs to be more that 4 g/m^3

Question 22

Why have deeper ponds in terms of sludge?

Answer 22

1.5 - 2m. so the overlying liquid controls the odor.

Question 23

Is it better to have a deeper pit near the inlet?

Answer 23

Yes, it stores incoming solids and creates ideal conditions for anaerobic digestion.

Question 24

How ofter does sludge removal take place?

Answer 24

Every 15 to 30 years.

Question 25

Why have an extra primary pond in terms of sludge?

Answer 25

So you can drain one to remove sludge.

Question 26

How well can sludge be air dried?

Answer 26

50-60% DS (what does that mean lol)

Question 27

Other than drying, what are other methods it can be removed?

Answer 27

• Slurry using suction cutter dredge or pumps on pontoon.

Question 28

How is sludge dewatered?

Answer 28

Portable belt press or centrifuge with polymer dosing.

Question 29

Where can sludge be disposed?

Answer 29

Landfill or forests depending on content.