Sewage a haunting problem in the city
[by OZONE group]
Sewage problems in Thiruvanathapuram
In Thiruvananthapuram Corporation area covered by the underground sewerage system is only 30%. The system was installed 25 to 35 year ago. The system services a total of 75,000 connections. The households in the remaining areas depends on various on-site systems namely, septic tanks, borehole latrine TUDP and community toilets with 8% of the population do not having access to safe sanitation disposal. The sewage farm is the only existing sewage treatment facility, which is receiving very limited sewage quantity (maximum up to 50 MLD). It was originally designed for only 8 MLD in 1938 and was commissioned in 1945.The quantity of sewage waste generated in Thiruvananthapuram is increasing and will continue to do so due to the additional water supply augmentation being
implemented under the JBIC aided project. Infiltration from the sewage farm area has caused
widespread ground water pollution in and around the sewage farm and along the down stream canal
Drainage system in the city
Thiruvananthapuram receives a very high rainfall. The average annual rainfall for the city is over 1,800 mm. The city has undulating topography, with ground level rising from MSL to 75m. The city has a large network of storm water canals and drains, (722 km- only 290 km of these drains are
covered). However, the storm water drains and canals carry treated/untreated sewage and large
amounts of solid waste.
Though the natural topography of the city has adequate slope to drain storm water, poor maintenance
of major drainage outlets and frequent blockages of primary drains cause local flooding and water
logging. Normally, water logging takes place during the period of high intensity and/or for extended
duration rains. During the monsoon season, water logging in low-lying areas occurs 5-6 times and
water levels rise from 0.6m to 1.2m. Water logging persists for 12 to 24 hours in the central part of
Thiruvananthapuram, and for 3 to 4 days in the southern part of the city.
Drainage Infrastructure. In a socio-economic survey carried out in the city was reported that drainage is perceived as one of the major environmental problems in the urban area and vulnerable/poor population are the most affected by localized flooding.
The key issues and challenges with respect to sewerage network in the city are:
- The existing sewerage network is very old and requires urgent rehabilitation, since frequent
overflows are common.
- Sewage overflow from the unsewered areas of the city and adjoining areas into the water body
creates nuisance and unhygienic conditions.
- The existing sewage farm at Valiyathura is overloaded, resulting in overflow and seepage to the
Parvathy Puthanar Canal and surrounding water bodies in the area and results in pollution of the
water bodies. This envisages the need for a modern Sewage Treatment Plant at Valiyathura.
- New development areas need to be brought under the sewerage network.
Treatment Plant, to treat the sewage being pumped to Muttathara. The total sewage load of the
extended Corporation area is 250 Mld. Full fledged Sewage Treatment Plants are also to be constructed
to cater to the requirement of outgrowths of Kazhakkuttom, Sreekaryam, Kudappanakkunnu,
Vattiyoorkavu and Kovalam and the anticipated sewage load is 60 Mld. A Sewage Treatment Plant of
10Mld is proposed to be constructed for the benefit of Medical College Campus, and a 15Mld Sewage
Treatment Plant is proposed to cater to the need of Container Terminal Area at Vizhinjam.
STORM WATER DRAINAGE
The drainage network of the city consists of two major rivers, few canals, their feeders and lakes. The two major rivers are Karamana and Killi which flow through the city area. There are a number of drains and leading drains in the city area like Pazhavangadi thodu, Uloor thodu, Pattom thodu, Kannanmoola thodu (Amayizhanjan thodu), Thekkenekara canal, Kariyil Thodu, and natural drains like Tettiyar thodu, Pangappara thodu, Kaimanam-Azhamkal thodu, Amathara thodu, Koori thodu, Vattakkayal Thodu. Other important drains contributing to storm water drainage to the city canals are Choozhampala thodu, Anathanathodu, Edanada thodu, Arayalloor Ela thodu and Thiruvallom Pallathukadavu thodu.
Water Conservation is another important area that needs immediate attention. Inspite of abundant water
resources, the city is facing water scarcity. Hence conservation of water is needed to restore the water for future needs. The developing areas surrounding the city are witnessing lot of construction activities where large scale filling of wet lands has resulted in blockage of natural drains and reduction in ground water recharge.
- The condition of existing rivers as natural drainage for storm water is deteriorating. Dumping of domestic wastes and non domestic waste from slaughter houses, markets, hotels, etc., discharge of sewages directly into the rivers and unscientific and indiscriminate methods of sand mining are resulting in the erosion of river bed and its banks.
- Due to reduced cross sectional area of rivers, flash floods have become common during down pour.
- Recurrent floods as a result of insufficient drainage are the perpetual problem faced by
Thiruvananthapuram city since several years. Thampanoor and East Fort areas are the worst affected with tremendous water logging.
- Transitory measures to prevent water logging is tried from time to time to ease the graveness of the situation. However, an abrupt rain of high intensity disrupts the city life considerably. A permanent solution to the problem is to be found.
- Regular stagnation of water results in environment and health hazards.
- The reclamation of water bodies and low lying areas or encroachments for development is the main reason for water logging. Most of the flood moderation zones inside the city have already been converted into concrete dwellings and apartments resulting in excessive run off.
- Improper maintenance of the already existing drains coupled with excessive run off is the root cause of flooding inside the city. In-depth study of the present status of the drains, their carrying capacity, anticipated flood discharge and the probable routing / rerouting may be devised and implemented for restoring / enhancing the status of drainage network inside the city to solve the issue to a significant extent.
Pollution in rivers
Lack of sufficient leading drains to take storm water to the river constantly erodes the river
Bunds. To tackle this issue, surface drains are to be constructed along the bund on the land
side to take the storm water for a length 5 km on either side at the required locations along with
Pollution in the surface water bodies:
The three main surface water bodies in Thiruvananthapuram are the Karamana River, Killi River and the Parvathy Puthanar, a man made canal. The Kerala State Pollution Control Board is continuously monitoring all the three water bodies. All these water bodies are contaminated with coliform indicating the contamination due to sewage. The quality of water in the lower reaches of the rivers is particularly not satisfactory.
Why does sewage pollution get so bad after rain?
The sewerage system has overflow points that act as safety valves. They are designed to protect public health by preventing sewage backing up into people’s homes if a problem occurs in the system.
In wet weather, overflows may be caused by rainwater getting into the sewer through faults in pipes or illegal connections, exceeding the capacity of the system. Overflows may also occur in dry weather due to problems such as a blocked pipe.
Why is sewage pollution a problem?
Sewage pollution carries
- Pathogenic protozoa such as Giardia and Cryptosporium that are a risk to human health
- Nutrients that can cause algal blooms and encourage weeds to grow and can kill native vegetation
- Chemicals such as detergents
- increased dissolved solids.
Testing for Sewage Pollution
A number of indicators are used to test levels of sewage pollution in creeks and rivers. An indicator is something that is easily tested to show that sewage pollution is present. The indicator does not tell you where the pollution came from (ducks, dogs, sewage system)
Faecal coliform are a bacteria that live in the guts of all warm blooded animals. They are not harmful to human health but are used to indicate the possibility of sewage pollution, which could mean the presence of more harmful bacteria and viruses. Methods of identifying viruses and bacteria directly are complicated and expensive, which is why indicators like faecal coliform or enteracocci are used.
Levels of faecal coliforms greater than 1,000 cfu/100 mL exceed the national guideline for secondary-contact recreational use of waterways (eg canoeing, paddleboats).
Ammonia is another substance monitored as an indicator of leakage from the system. Like faecal coliforms, this substance is found at high concentrations in raw sewage. While no specific guidelines are set for total ammonia, levels of 1 mg/L help target areas for investigation.
|How can your help to reduce sewer overflows?|
1. CRACKED PIPES
Tree roots can invade even the smallest cracks in pipes. As the roots grow, so does the size of the cracks. This lets in rainwater. Tree roots can also block the pipes causing sewers to backup and overflow. Cracked pipes have to be repaired or replaced. Careful thought needs to be given to the location of thirsty trees.
2. BROKEN PIPES
Broken pipes can occur in both Sydney Waters and householders systems. Sydney Water is responsible for inspecting, maintaining and repairing the mains system, and property owners are responsible for sewer pipes and downpipes on their land. Broken sewer pipes not only let stormwater in, they can also allow untreated waste to enter the soil and create unhealthy conditions. If you suspect broken pipes, have your system inspected by a licensed plumber.
3. BOUNDARY TRAPS
Many, but not all, properties have a boundary trap. This acts as an inspection point on the sewerage system. It also stops sewer odours from reaching the property. If the boundary trap is set below ground level and it’s lid or concrete rim is damaged, stormwater can get in. There can also be a problem if the vertical riser is cracked.
4. DIRECT CONNECTION
Stormwater downpipes are not allowed to be connected to the sewerage system. All water from your roof should be connected to the local councils stormwater system. Sometimes direct connection to the sewerage system may seem easier. The effect of doing so is overflows of diluted raw sewage further down the system.
5. INSPECTION HOLES
Poorly fitting cracked or broken inspection holes on the mains sewer system can let water into the sewerage system.
6. LOW-LYING GULLIES
A gully is an open pipe which is covered with a grille and found just outside your building. It is there to release any backflow from blocked sewer pipes and make sure it doesn’t overflow inside the house. If the ground around the gully is built up too high, it can let stormwater into the sewerage system. A plumber can lift the gully or lower the ground around it.
On-site versus off-site sanitation?
On-site sanitation is often (and should be) the first option when considering a sanitation intervention. Such systems have very distinct advantages, not least because they are individual systems, so the disposal of faecal material is dispersed over a wide area, and not centralized as with a conventional sewage treatment works. One of the main disadvantages with centralized facilities is that when they go wrong, the resulting problems can be very acute. From a health point of view, there is not much difference between any of the different options for sanitation (either on or off-site) — so long as they are all functioning properly. It is largely a question of convenience; an off-site system where wastes are flushed off the owner’s property is more convenient as it gets rid of the problem from the owner’s property. Off-site sanitation is usually much more expensive than on-site. There are instances, however, where off-site sanitation is deemed necessary— because of unsuitable ground or housing conditions for on-site systems,
or because of a community’s commitment to an off-site system. There is a certain amount of prestige in having an off-site connection; peer pressure is often a significant motivating force. Once the decision has been made to implement an off-site system, sewers become a necessity. Water has a large dispersion, dilution and carriage capacity, and is, therefore, used as the carriage medium in most sewer systems. Usually, potable water is supplied to the house and is used for flushing toilets, and as much as 40 percent of household water use may be used for this purpose. Some countries do use dual supply systems where no portable water (often sea water) is used for toilet flushing, but such a system requires more infrastructure and has obvious capital cost implications. Therefore, most sewer systems are
heavy users of precious potable water supplies, which should be a factor when considering their implementation, especially in water-poor areas.
Traditionally, sewage has been seen as a problem requiring treatment and disposal. Most conventional sewage treatment options are based on approaches to Northern countries’ problems, which has usually meant a reduction in biodegradable organic material and suspended solids, plus perhaps some nutrients (nitrogen and phosphorous). Treatment has involved the ‘removal’ of these pollutants, but removal is usually conversion to another product, usually sludge. The disposal of sewage sludge is a major consideration in many locations, and it is often seen as an offensive product which is either
dumped or burned.
The priorities in developing countries are often different from those in developed countries. Often the main issue is how to control pathogenic material, and any form of sanitation (on or off-site) should have this as its main objective. There are treatment options which can remove pathogenic material, notably waste-stabilization ponds.