Stabilization ponds

Stabilization ponds

1. What are stabilization of ponds ? Explain the algae -bacteria symbiosis in an oxidation pond with neat sketch.

2. STABILIZATION PONDS Stabilization Ponds is Biological Treatment Systems in which stabilization of organic material is carried out by Bacterial oxidation/ photosynthetic reduction in algae. Stabilization Ponds are also known as lagoons or oxidation ponds.

3. STABILZATION POND

4. Stabilization ponds are large, shallow ponds designed to treat wastewater through the interaction of sunlight, bacteria and algae. The pond, typically 1-2m deep. Decomposition by symbiotic action of algae and bacteria. Top layer is Anerobic while the bottom layer is anaerobic. Algae grow within the pond and utilize the Carbon dioxide, Sulphates, nitrates, phosphates, water and sunlight and gives oxygen that is available to bacteria and other microbes This O2 is used by the aerobic bacteria in the oxidation pond to breakdown the organic matter in wastewater The broke down solids settle down in the ponds, resulting in effluent that is relatively well treated.

5. STABILZATION POND

6. During the process of photosynthesis, The algae release oxygen needed by aerobic bacteria. Mechanical aerators are sometimes installed to supply yet more oxygen, thereby reducing the required size of the pond. Sludge deposits in the pond must be eventually removed by dredging. Algae remaining in the pond effluent can be removed by filtration or by a combination of chemical treatment.

7. MECHANISM OF WASTE TREATMENT First, the bacteria present in the oxidation pond will oxidize the organic waste of the domestic as well as industrial sewage. By doing this, bacteria release carbon dioxide, water and ammonia. The algal growth occurs in the presence of  sunlight . It utilizes the  inorganic waste  formed by the organic matter decomposition and releases oxygen.

8. From the above two mechanisms, the algae and bacteria work  corporately  to fulfil each other’s requirement. The bacteria use  oxygen  released by the algae, to  oxidize  the biodegradable organics. A  carbon-dioxide  release as the result of organic waste oxidation by the bacteria is used by the algae to undergo a  reduction  of inorganic waste like nitrogen, phosphorus compounds etc. As the oxidation and reduction reaction co-occurs, an oxidation pond also refers as “ Redox pond ”. The sludge of oxidation pond may use as a manure for the  irrigation processes .

9. PROCESS INVOLVED IN OXIDATION POND The process involved in the conversion of industrial, domestic wastewater into simple form includes: First, through the  inlet  system, the industrial, domestic wastewater influents into the oxidation pond. Then, the bacteria utilize the biodegradable organics and convert it into inorganic compounds by releasing  carbon dioxide . Achromobactin, Proteus, Alcaligenes, Pseudomonas, Thiospirillum , Rhodothecae etc. are the following genera of the bacteria that predominates in the stabilization pond.

10. The algal biomass in the oxidation pond utilizes the inorganic compounds in the presence of  sunlight  and  carbon-dioxide  released during the oxidation of organic waste. Chlorella, Euglena, Scenedesmus and Microcystis are the most common genera of algae that predominates in the stabilization pond.

11. Remaining non-biodegradable or solid organic wastes  settle down  in the bottom of stabilization pond as  Sludge . The anaerobic bacteria convert it during the night and in the absence of oxygen. The anaerobic bacteria first convert the insoluble organic waste into soluble  organic acids  like ethanol. Further decomposition of organic acids by the anaerobic bacteria releases  H 2 S ,  NH 3 ,  CH 4 ,  CO 2  etc. The treated water releases out through  outlet  system of a stabilization pond. Sludge deposits remove out from stabilization pond by the method of  dredging . The algal and bacterial biomass can separate out either by  filtration  method or the combination of chemical treatment and settling process.

12. FAVOURABLE CONDITIONS Secondary treatment of wastewater in an oxidation pond requires the following environmental factors: 1.Sunlight 2.Micro Organisms 3. Oxygen 4. Wastewater Quality 5. Pollutant Load

13. ADVANTAGES OF STABILIZATION PONDS The stabilization pond can reduce the  biological oxygen demand  up to 90% naturally. It is a  simple  method to operate, does not require sophisticated equipment. Oxidation pond is a practical and  effective  method for the wastewater treatment of domestic and trade wastes in the tropical areas. The operation of a stabilization pond does not require much labor-power. It is an  economical  method for the treatment of wastewater from small and isolated units.

14. DISADVANTAGES OF STABILIZATION PONDS The construction of a stabilization pond requires  more land area . The  maintenance  is quite intricate. Sometimes, it gives a  foul smell  and  mosquito menace  during the process if not appropriately maintained. There may get a chance of  effluent seepage  into the ground water, which can ultimately cause ground water pollution.

15. CONCLUSION Therefore, we can conclude that the oxidation pond is a biological system which takes about 10-40days of  detention time . This method can load organic matter up to  300-150Kg/hectare/day  and having a length of  50-100m , a width of  30-50m  and a depth of  0.9-1.5m . Usually, an oxidation pond can hold water up to  0.3m   and settled sludge up to  0.02m . The decomposition of bio-organics produces a  foul smell , that’s why the stabilization pond is kept away from the residential areas. The use of  sodium nitrate  can avoid foul odour during the wastewater decomposition.