FREQUENTLY ASKED QUESTIONS Index
| What is sewage? What is its typical quality? | Go to Top | |
| We use the water for various domestic applications such as drinking, cooling, bathing, toilets & washing. About 135-lpcd water consumption is considered by WHO. Generally 85-90% of water consumption becomes wastewater. Ideally, sewage is wastewater generated from toilets only but generally all domestic wastewater is collectively called sewage. Various organic as well as inorganic impurities get added into it. Typical wastewater characteristics of domestic sewage are as follows | ||
| Characteristic | Range of values (gpcd) |
| BOD5 | 200 - 300 |
| COD | 500 - 600 |
| Total Organic carbon | 100 - 150 |
| Total Solids | 1200 - 1500 |
| Suspended Solids | 70 - 145 |
| Grit | 5 - 15 |
| Alkalinity as CaCO3 | 20 - 30 |
| Chloride | 4 - 8 |
| Total Nitrogen as N | 6 - 12 |
| Total Phosphorus as P | 0.8 - 4.0 |
| However, the quality considered by Manual on sewerage and sewage treatment considers very high values, which normally are not encountered. |
| What is sullage? | ||
| Out of the total domestic waste, the wastewater generated from kitchen and bathrooms is called as sullage. Sullage is much leaner in strength. | ||
| How does the sewage treatment process work? | Go to Top | |
| Generally, domestic sewage consists of suspended solids, organics. Organic contributes to BOD. | ||
| Treatment system focuses on removal of suspended solids, BOD, COD to the desired limit. System removes suspended solid through the sedimentation process, while BOD reduction takes place inside biological system. | ||
| Typically, treatment scheme for domestic wastewater treatment consists of physicochemical treatment followed by biological system. | ||
| What are various technologies available for biological treatment of sewage? Is it possible to meet the standards set for safe disposal of treated sewage? | ||
| Both aerobic as well as anaerobic technologies can treat the sewage biologically by selecting suitable bacteria. These technologies can be further grouped into attached growth - where bacteria are grown on the support media and suspended growth type - where bacteria are grown in the effluent itself. In Ion Exchange (India) Ltd., we generally employ aerobic technologies such as | ||
| It is surely possible to treat the sewage efficiently to meet disposal standards |
| How to choose appropriate technology, which suits to your needs? | Go to Top | |
| Choice of appropriate technology is mainly governed by effluent flow, area requirement, economical aspects and treated water applications, etc. | ||
| Refer brochures for various technologies for more information. | ||
| What will be energy requirement for the treatment? | ||
| For aerobic technologies, the energy requirement to treat 1 kg BOD/hr is about 1.2 - 1.4 HP. | ||
| Is there any requirement for nutrient addition during biological treatment? | Go to Top | |
| Nitrogen (N) and Phosphorous (P) are main ingredients of a cell are required for bacterial cell growth. Generally, sufficient amount of N and P are present in the domestic wastewater, so no requirement for nutrient addition. For industrial wastes, sometimes it becomes necessary. | ||
| Is it possible to reuse the treated domestic sewage for any other use? | ||
| Yes, treated sewage water can be used for gardening, car washing, and toilet flushing system, etc. after proper polishing tertiary treatment. | ||
| Is the tertiary treatment necessary? | Go to Top | |
| Tertiary treatment is necessary where treated wastewater is reused again for any application. As domestic sewage consists of various microorganisms, of which some may be pathogens. To safeguard their contact with human, it is must to kill microorganism to 100% prior to its reuse. Various technologies are available for microbial sterilization like UV System, Ozonation, Indchlor, Chlorination - Chlogen etc. Similarly, to remove residual suspended matter, proper filtration - | ||
| is required. In nutshell, type of tertiary treatment depends upon the end use. If the recycled water is to be used for high end applications DM or RO process are also employed. |
| Will there be odor nuisance in surrounding areas of sewage treatment plants? | ||
| Generally, odor problem occurs during biological treatment due to escape of gases like CH4, H2S, Ammonia, etc. but as our technologies are based on aerobic treatment, there will be no treat for odor nuisance in the surrounding areas. | ||
| Is the nutrient removal possible during domestic sewage treatment itself? | Go to Top | |
| Excess of nutrients is also not advisable and nutrients need to be removed. Nutrient removal is very much possible during wastewater treatment itself. | ||