A Presentation on Oxidation Ponds & Lagoons

Oxidation Ponds What are Oxidation Ponds ? Oxidation Pond is an open, flow through earthen basin of controlled shape specially design and constructed to treat sewage and bio-degradable industrial waste by natural processes involving bacteria and in many instances algae.

Types Of Oxidation ponds Aerobic Ponds Anaerobic Ponds Facultative Ponds Maturation or Tertiary Ponds

Applications Type of Ponds

Applications

Aerobic

Nutrient removal, treatment of soluble organic waste & effluents from waste water treatment plants.

Anaerobic

Treatment of domestic and industrial wastes.

Facultative

Treatment of untreated screened waste water and industrial wastes.

Symbiosis Algae Solar Energy

New Algae

CO2, NH3, H2O O2

Organic Bacteria

New Bacteria Bacteria

Aerobic Ponds The aerobic pond is shallow pond in which light penetrates to the bottom there by maintaining active algal photosynthesis through out the entire system.

Light Energy from Sun

ALGAE

Organics from Waste Water

AEROBIC BACTERIA

New Algal Biomass

New Bacterial Biomass

Diurnal Variations in Aerobic Ponds Diurnal variation in DO concentration Diurnal variation in pH Extreme values of these, in either direction may be detrimental to microbial activity.

Design Considerations Parameter

Value

Depth in mts.

0.15-.5

Retention time (day)

2-6

BODu loading( lb/acre-day)

100-200

BODu removal(%)

80-90

Algae concentration(mg/l)

100-200

Re-circulation ratio

0.2-2.0

Effluent suspended solids concentration(mg/l)

150-350

Problems Nuisance vegetation Inhibitory temperatures Oxygen retention Shock loads

Anaerobic Ponds These ponds requires no D.O. for microbial activity as the organisms use O2 from compounds such as NO3, SO4 as their hydrogen acceptors and give end product such as methane, carbon dioxide etc.

Anaerobic decomposition  It take place in two separate but inter related steps :1.

Decomposition of dissolved organic waste by acid producing bacteria to organic acids (such as acetic propionic acid) and,

2. Further decomposition of these acids to the end

products of methane, carbon dioxide and water by methane producing bacteria.

H2O, CO2

Organic Wastes

Acid producing Bacteria

Bacterial Cells

H2O, CO2, CH4

Methane producing bacteria

Bacterial Cells

Facultative Ponds These are neither fully aerobic nor fully anaerobic. They are often about 1 to 2 m in depth and favor algal growth along with the growth of aerobic, anaerobic and facultative microorganisms. Such ponds are predominantly aerobic during day light as well as for some hours of the light. In the few remaining hours the pond bottom may turn anaerobic.

Zones of facultative pond 1) Aerobic zone 2) Anaerobic zone 3) Facultative zone

The decomposition of incoming organic waste and products of anaerobic decomposition is done by facultative bacteria.

Wind Sunligh t

CO2

Biomass

Organic acids & Compounds of C, N, P, S Biomass

Anaerobic Bacteria Sludge Blanket Impermeable lining

Anaerobi c Zone

Facultative Zone

Aerobic Bacteria

Anaerobi c Zone

(CO2, NO2, PO4, SO4)

O2

Aerobic

alga e

Maturation / Tertiary Ponds These are similar to aerobic ponds but are very lightly loaded with organic wastes. Generally used for upgrading effluents from conventional secondary treatment processes.

Reasons For Poor Performance of Oxidation Pond  DO level in the pond during night & early morning hours

was almost zero.  BOD removal efficiency was only 50-58%  BOD loading rate was 91.20 kg/day as compared to the design BOD of 81kg/day.

LAGOONS  Lagoons are deep waste stabilization ponds -like bodies of water or basins designed to receive, hold, and treat wastewater for a predetermined period of time by artificial means of aeration.  In the lagoon, wastewater is treated through a combination of physical, biological, and chemical processes.

TYPES OF LAGOONS According to the microbial activity in the aerated lagoonsAerobic aerated lagoons. Facultative aerated lagoons.

AEROBIC AERATED LAGOONS  Dissolved oxygen is present throughout much of the

depth of aerobic lagoons.  They tend to be much shallower than other lagoons.  They are better suited for warm, sunny climates, where they are less likely to freeze.  HRT = 2 to 10 days  SS concentration between 60 to 300mg/l  The BOD removal is of order of 75 to 85%  Oxygenation requirement is of order of .7 to 1.3 kg per kg of BOD removed.

Units of aerobic lagoon 1) The mechanical surface aerators so that solids do not

settle to bottom of tank.

2) The other unit is settling tank for removal of

suspended solids .

FACULTATIVE AERATED LAGOONS  Three types of zones are present

Aerobic Zone. Anaerobic Zone. Facultative Zone.  HRT is higher than aerobic lagoons because time requires for the solids to settle and for many pathogens viruses to either die off or settle out.

Facultative lagoons  SS concentration is ranging from 30 to 150 mg/l  Detentions time ranges from 3 to 5 days .  BOD removal are of order 75 to 90%  Oxygenation requirement is about .8 kg per kg of

BODs

Two, Three, or Four Lagoons Are Better Than One  Each lagoon cell has a different function to perform,

and a different kind of lagoon design may be used for each cell.

In Series When lagoons operate in series, more of the solid material in the wastewater, such as algae, has an opportunity to settle out before the effluent is disposed of.

In Parallel This system design is particularly useful in cold climates or where lagoons are covered with ice for parts of the year

Operation And Maintenance For Aerobic Lagoons Any earthen structures used as impoundments must be periodically inspected. If left unchecked, rodent damage can cause severe weakening of lagoon embankments. In submerged diffused aeration, the routine application of HCl gas in the system is used to dissolve accumulated material on the diff units The use of submerged perforated tubing for diffused aeration requires maintenance and cleaning on a routine basis to maintain design aeration rates

Operation And Maintenance For Facultative Lagoons Most facultative lagoons are designed to operate by gravity flow. The system is not maintenance intensive and power costs are minimal because pumps and other electrically operated devices may not be required. Earthen structures used as impoundments must be inspected for rodent damage.

Applicability Type of Lagoon

Application

Aerobic Lagoon

Municipal and industrial wastewaters of low to medium strength.

Facultative Lagoon

Treated raw, screened, or primary settled municipal wastewater and biodegradable industrial wastewaters.

Limitations For Aerated Lagoons Aerated lagoons may experience ice formation on the water surface during cold weather periods Reduced rates of biological activity also occur during cold weather Formation of ice on Floating Aerators. For facultative Lagoons The inability of the process to meet a 30 mg/L limit for TSS due to the presence of algae in the effluent. Odors may be a problem in the spring and fall during periods of excessive algal blooms and unfavorable weather conditions

References: 1. www.oilgae.com/ref/glos/oxidation_ponds.html  2. www.microbiologyprocedure.com  3. www.eco-web.com/cat/2.5.html  4. www.eco-web.com/cat/2.5.html

 5.www.mazzei.net/applications/wastewater/odor.htm  6.www.brighthub.com/engineering/civil/articles/50611.as

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