Rapid urbanization in the country is putting unprecedented pressure on infrastructure in the cities. Therefore, management of liquid waste (sewage and septage) becomes a challenge for urban local bodies.
Indian cities have a combination of sewerage networks and onsite sanitation systems (OSS).As per Census 2011, 37 percent of urban households in the country were dependent on OSS that includes septic tanks, twin pit latrines and such alternatives. Septic tanks are the most common type of OSS. However, experience show that in various part of the nation, septic tanks are not constructed as per the stipulations of Bureau of Indian Standards (BIS) and guidelines of Central Public Health and Environmental Engineering Organisation (CPHEEO). Poorly designed tanks, tend to choke up more readily, leading to overflow of sewage onto ground surface. Also, the systems are underperforming in terms of desired level of treatment.
At the same time, management of sewer networks is increasingly becoming a challenge in Indian cities due to congested spaces in high-density urban areas and breakdowns caused by various types of digging activities as well as ingress of undesirable solids through open sewer manholes. Further, there are different topographic challenges for laying sewers, poor construction quality and economic considerations, which causes choking and sewer overflows. There are caseswhen the storm water runoff is allowed to flow into sanitary sewers due to lack of/ inadequate capacity of storm water drains. This storm water deposits large quantity of silt and municipal garbage in the sewers.
Once clogged, sewers tend to cause backflow onto the urban space and require immediate rectification. Various type of specialised equipment-, jetting machines, grabbers and rodding equipment are used by municipal agencies to remove the obstruction along with suction machines to pump out the wastewater for alternate disposal.
At times due to various reasons such as non-suitability of available equipment and inaccessibility of certain type of equipment, instances of manual cleaningof sewers/ septic tanks are reported.
The Challenges of Cleaning Sewers and Septic Tanks
Sewer networks require regular cleaning to prevent possible choking of drains. However, frequent blockages occur in the drains due to accumulation of silt, municipal garbage including rags and plastic and construction debris and due to lateral expansion of roots that clog the drains. Similarly, septic tanks systems also need periodic maintenance.
Cleaning of sewer and septic tanks are routine activities carried out using mechanized equipment and through manual means. Urban local bodies (ULBs) in the country procure sewer suction equipment, sewer-jetting machines or a combination of both and sewer rodding equipment with various accessories. Sometime small and medium town cannot afford such equipment. Moreover, semi-skilled operators are required to operate the equipment to prevent damage to sewer linings and manholes. De-sludging of septic tanks is critical in high-density urban areas. However, many a times, providing access to the site is a problem for equipment due to narrow streets or steep slopes in hill areas.
In such situations, when use of mechanical equipment is not feasible to unclog sewers, human entry through manholes has remained the option of choice. Similarly, wherever de-sludging machines cannot be used, septic tanks are manually cleaned by using ordinary tools.
In addition to the above stated technical issues, the overall financial sustainability of procuring and operating heavy-duty equipment is also a challenge for municipal administrators.