Septic tanks do not treat the waste but only store it thus they basically just postpone the problem of treating the waste and act as containers of waste material.
In many rural areas no proper equipment is available to pump out the waste matter from the septic tanks and many a times people manually clean the septic tanks which is tantamount to manual scavenging, a practice that is morally repugnant, dehumanising and against the law.
The agencies that “clean” the septic tanks do not treat the waste – they just dump it in the water bodies or ditches, thus polluting the environment.
Working Features | Septic Tank | Bio-Digester |
Waste Degradation | Aerobic dominant | Anaerobic |
Waste Decomposition | Only 30% pathogen reduction | Up to 99% pathogen reduction |
Additives | Periodic addition required | One time charge of Bacterial Inoculum. |
Sludge Formation | Yes | No |
Maintenance | Periodic removal of sludge, to be emptied every 2 years or earlier as per IS 2470 norms. High Maintenance Costs. | Maintenance-free. |
Discharge from Tank | Odorous (hydrogen sulphide and ammonia gases), sludge formation and hazardous waste . Discharge water is unsafe for any kind of use and has to be disposed of safely. The discharged water contaminates the ground / water bodies. | Odourless, colourless and hazard-free waste (water only)Discharge water is safe to be used for irrigation, gardening or to be let off into water bodies or over the ground. It does not contaminate. |
Sensitivity towards Cleaning Agents | Cannot tolerate toilet cleaning agents | Bacteria conditioned to remain unaffected by cleaning agents up to permitted limits |
Size of the system | Three times bigger than the Bio-Digester, hence costly to construct and occupies more space a major constraint in the urban areas | One third the size of the Septic Tank, hence economical and has a smaller footprint leading to lower construction cost. |
Impact on Environment | Significant | No impact…100% Eco-Friendly system |
EFFLUENT TEST RESULTS – COMPARISION | ||
Parameter | Septic Tank | Bio-Digester |
pH | 6.7-7.5 | 7.0-7.2 |
Turbidity (NTU) | 500-800 | 70-90 |
Total Suspended Solids (mg/L) | 150-300 | 90-120 |
TDS (mg/L) | 500-850 | 350-450 |
VS (mg/100ml) | 50-60 | 20-30 |
COD (mg/L) | 1200-2000 | 250-300 |
BOD 5 (mg/L) | 350-500 | 70-120 |
Coliforms (MPN/ml) | > 3,000 | 300-350 |
Working Features | Septic Tank | Bio-Digester |
Waste Degradation | Aerobic dominant | Anaerobic |
Waste Decomposition | Only 30% | Up to 99% |
Maintenance | Periodic removal of sludge, to be emptied every 2 years as per IS 2470 norms | Maintenance-free |
Mechanical Sludge Removal | Pumping device required | No sludge removal required |
Discharge from Tank | Odorous, sludge formation and hazardous waste | Odourless, colourless and hazard-free waste (water only) |
Space for 300 Users | Three times more than the Bio-Digester, hence costly to construct and occupies more space | One third space required compared to Septic Tank, hence economical and has a smaller footprint |
Sensitivity towards Cleaning Agents | Cannot tolerate toilet cleaning agents | Bacteria conditioned to remain unaffected by cleaning agents up to permitted limits |
pH | 6.7-7.5 | 7.0-7.2 |
Turbidity (NTU) | 500-800 | 70-90 |
Total Suspended Solids (mg/L) | 150-300 | 90-120 |
TDS (mg/L) | 500-850 | 350-450 |
VS (mg/100ml) | 50-60 | 20-30 |
COD (mg/L) | 1200-2000 | 250-300 |
BOD 5 (mg/L) | 350-500 | 70-120 |
Coliforms (MPN/ml) | > 3,000 | 300-350 |