Wastewater Treatment Systems Using Ponds
It's a shallow pool of water in an earthen basin that's exposed to the light and air. The pond allows for a longer period of retention, ranging from a few days to weeks. The symbiotic connection between bacteria and algae helps to purify wastewater.
Aerobic, facultative, and anaerobic ponds are classed based on the type of biological activity that occurs within the pond. In hot climates, they are less expensive to build and run, than traditional treatment systems, hence they are referred to as low-cost treatment systems.
The majority of the ponds are of a facultative character.
This sort of pond has three zones:
1: Algal photosynthesis and aerobic biodegradation occurs at the top zone, which is an aerobic zone.
2: Organic materials in wastewater and cells formed in the aerobic zone settle down and undergo anaerobic breakdown in the bottom zone.
3: The intermediate zone is a mix of aerobic and anaerobic activity. In this zone, facultative bacteria are responsible for the breakdown of organic waste. Because of the presence of a top aerobic zone, the anaerobic response is no longer a bother.
The successful functioning of a facultative stabilization pond requires the maintenance of an aerobic state at the top layer, which is dependent on solar radiation, wastewater properties, temperature and BOD loading.The efficacy of these ponds is equivalent to that of traditional wastewater treatment methods.
How do you build a Facultative stabilization pond?
The pond's oxygen resources are equivalent to the applied organic loading during design.
Photosynthesis is the primary generator of oxygen, and it is powered by solar energy. Solar energy is tied to geographical, meteorological, and astronomical phenomena, and it changes mostly with the time of year and the elevation of the location. If the quantity of solar energy in Cal/m2.day and the efficiency of light energy conversion to fix energy in the form of algae cells are known, the yield of photosynthetic oxygen may be computed immediately.
Part of the organic matter in facultative ponds is assumed to decompose anaerobically, and the photosynthetic oxygen output is equal to the remaining organic matter to sustain aerobic oxidation.
The organic loading on the pond in kg of BOD per hectare per day may be calculated using ponds with facultative properties.
The photosynthetic oxygen production is equal to the remaining organic matter to enable aerobic oxidation, and portion of the organic matter is believed to undergo anaerobic degradation.
The organic loading on the pond in kg of BOD per hectare per day may be calculated using:
Divide by factor (1 + 0.003 EL) to adjust the organic loading for altitudes above mean sea level. Where ‘EL’ denotes the elevation of the pond location above MSL in meters. The pond area may be raised by 3% for every ten percent fall in the sky clearance factor below 75 percent.
Typical pond-based treatment plant flow chart
The ponds can be connected in a series or in a parallel configuration. The treated effluent can be chlorinated if desired. In the ponds, the main process after screening might be supplemented with secondary treatment. Screens are supplied ahead of the first pond in all of the flowcharts of the ponds in Figure below.
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