Mechanised cleaning of Septic Tanks: a socio-technological review

 Mechanised cleaning of Septic Tanks: a socio-technological review

Authors: Linda Jasline, Bhavesh Narayani, Divanshu Kumar & Prof. Prabhu Rajagopal, 
Solinas Integrity Private Limited and Center for Nondestructive Evaluation, IIT Madras 

 

1. Societal context and Background
   
   Dignity is an inalienable right which is part of the fundamental right to life. Justice systems all over the world have held human dignity to be the most important, fundamental, inalienable and transcendental of rights. Yet, even after more than 70 years of independent India we find a section of the society, the scavenging community, being deprived of this and being predominantly engaged in the practice of manual scavenging. The Supreme Court found in 2014 that there were over 9.6 million dry latrinesin India which required manual emptying. In other data points, there are over 75 million households, which are connected to septic tanks that may require manual scavenging, comprising 40% of the households.  Traditionally, entire cleaning of the septic tank is done by manual scavengers, as shown below in Fig.1

Indian law, the Prohibition of Employment as Manual Scavengers and their Rehabilitation Act 2013, which is the current law against manual scavenging, prohibits dry latrines and all kinds of manual cleaning of excrement as well as cleaning gutters, sewers, and septic tanks. This was an improvement from the earlier 1993 law which only gave importance to dry pit latrines. The act of 2013, apart from recognizing this dehumanizing practice arising from the inequitable caste system, also recognizes how manual scavengers are prone to serious injury and are always at a risk of death. The act envisages that sewers should be cleaned mechanically while manual scavenging will only be permitted in exceptional cases, with safety equipment by the employer. If unfollowed, this is considered a criminal offence even when it does not result in injury or death. The offender can be charged with a maximum of five years imprisonment and a fine of five lakh rupees. Additionally, an association of safai karamcharis, called Safai Karamchari Andolan, led by Bezwada Wilson (Ramon Magsaysay Awardee) has been instrumental in bringing the attention of common public to the issue and rehabilitating some of them.

Despite these efforts the practice continues unabated. Deaths arising from manual scavenging are commonplace in India, (1000+ people die every year cleaning these tanks) and there has been press attention turned to the scavengers’ dangerous conditions of work in the National Capital. A 2019 study done by the WHO (World Health Organization) showed that “weak legal protection and lack of enforcement” of the laws as well as the sanitation workers’ poor financial status (as the rehabilitation schemes remain ineffective) were the major contributors to the practice still existing. India is a federal democracy and sanitation remains under the purview of the states. Hence the implementation of the laws of manual scavenging remains under them, without any compulsion and commitment. Though some municipal bodies have begun adopting machinated sewer and septic tank cleaning in this attempt, this is occurring at a very slow pace. Lastly, this is a complex problem at the intersection of a complex caste system (shaping public perception) and lack of technological development towards solving this issue.

2. Technological Solutions from India/elsewhere addressing Manual Scavenging

Fig. 2: Photograph of giant ball for sewerage lines http://theballreport.com/the-sewers-of-paris-are-cleaned-by-giant-balls/	Fig.3: Photograph of a sewer cleaning machine https://www.mylaporetimes.com/2010/12/new-sewage-cleaning-machine-for-zone-x-a/
Fig.4: Photograph of a sewer jetting machine Image source	Fig.5: Photograph of a Mini sewer jetting machine https://www.thenewsminute.com/article/how-hyderabad-getting-rid-manual-scavenging-its-mini-sewer-jetting-machines-106023

Minimal effort was given to finding a solution for this demeaning problem for several decades and no lessons were learnt from other countries in this aspect. In France giant balls, but smaller than sewerage lines, are pushed using water at high pressure to unclog the sewers. Until now, there have been a few solutions that have been found in India. Some of the technologies that are available in the Indian market for sewer system cleaning are sewer drain jetting trucks, sewer jetting and flushing machines, gas detector masks, and sewer cleaning robots.

Apart from equipping the workers with technology, several rules must be followed to ensure safety. Safety training is critical and all employees associated with the job must undergo it. Written instructions and procedures need to be provided to the workers and continuous supervision during the job must be done. To operate the equipment, the workers present at the site need to be familiarized with how to operate. In addition to that, workshops are to be conducted at least once every two years to update them on the improved methods and techniques. Manual scavengers need training to use the dedicated technologies available in the Indian market thus enabling them to live a life of dignity.

3. The approach that may work

Taking a socio-technological approach to solve this problem could provide us a potential solution. Firstly, we need to understand the problem of cleaning fundamentally and then look at technological solutions. Moreover, we need to work on ground with people and empower them to leverage these technologies for themselves, thereby contributing to their financial wellbeing.

Cleaning hard sludge from the bottoms of septic tanks and sewer lines is vital in the sanitation industry. Septic Tank is a poisonous environment, filled with a semi-solid and semi-fluid human fecal material that makes up about two-thirds of the tank. Diving further, the fecal sludge actually starts solidifying into a clay-like substance and toward the bottom it gets rock-hard. Once filled, they are required to be cleaned every 2-5 years to stop sludge overflow and groundwater contamination. However, this results in the gradual accumulation of un-pumpable sludge at the bottom of the pit, which eventually fills the latrine and forces it to be abandoned. This is where manual scavengers come into the picture. The workers who are often assigned to clean the septic tanks die due to suffocation, exposure to toxic gases, that results in skin and breathing disorders.  This is a stigmatized occupation that operates from the underbelly of social negligence

4. Solinas, an IIT Madras incubated startup developing HomoSEP Robot to aid Sanitation workers for Cleaning Septic Tanks

A team led by Mr. Divanshu Kumar at the start-up Solinas Integrity Private Limited in collaboration with Dr. Prabhu Rajagopal at the Center of Non-Destructive Evaluation (CNDE), IIT Madras has been developing the ‘HomoSEP’ robot for automated homogenization & cleaning of Septic Tank contents. In the last year, the team has successfully completed trials of the next version of HomoSEP robot (v2.0) which is more rugged and miniaturized for portability under laboratory, mock-up and field conditions. A start-up “Solinas Integrity Private Limited” led by Mr. Divanshu Kumar and Dr. Prabhu Rajagopal in collaboration with Center of Non-Destructive Evaluation (CNDE), IIT Madras has been developing the ‘HomoSEP’ robot for automated homogenization & cleaning of Septic Tank conHomoSEP robot developed by Solinas Integrity Private Limited in collaboration with Center of Non-Destructive Evaluation (CNDE), IIT Madras

This HomoSEP robot will aid manual scavengers in cleaning the hard sludge without entering the potentially dangerous atmosphere of a septic tank. HomoSEP is a compact robot made up of five main modules. The bottom module can homogenise hard sludge with water to create a pumpable slurry, and the feeding machine module can push and pull the bottom module inside a septic tank manhole at a depth of 3-5 metres. The portable module is mounted on a mobile frame to hold the whole robot at actual septic tank sites. The electronic module is configured so that the entire robot can be operated by the manual scavengers with a single remote. The suction module is intended to suck the homogenised slurry from the Septic tanks.

Solinas solution, the HomoSEP robot will be available from December 2021 for cleaning septic tanks. This robot will be operated by  a worker using a portable remote control panel and screen.

HomoSEP robot developed by Solinas Integrity Private Limited in collaboration with Center of Non-Destructive Evaluation (CNDE), IIT Madras

 

About Authors :
1. Mr. Divanshu Kumar, Heading Involve Education & Solinas Integrity,  IIT Madras | PM Awardee, 
https://www.linkedin.com/in/divinvolve/?originalSubdomain=in
2. Mr. Bhavesh Narayani, Head of Product Development at Solinas Integrity, IIT Madras
https://www.linkedin.com/in/bhavesh-narayani-32a1a8144/?originalSubdomain=in
3. Ms.Linda Jasline, Project Manager at Solinas Integrity Pvt. Ltd, IIT Madras https://www.linkedin.com/in/lindajasline/
4. Prof.Prabhu Rajagopal, Faculty in charge, Centre for Innovation at Indian Institute of Technology, Madras
https://www.linkedin.com/in/prabhu-rajagopal-041ab74/?originalSubdomain=in

Rainwater Harvesting and Groundwater Management in Urban Areas

 Authors: Nikita Harikishan, researcher and project lead at Biome Environmental Trust and Shubha Ramachandran team lead of Water Team at Biome Environmental Trust

 

Rainwater harvesting – Science in action

Rainwater harvesting has been in existence for thousands of years. It is a very intuitive and actionable idea. Still, there is complex science behind rainwater harvesting and groundwater management, including rainfall patterns, climate variability, hydrogeology and the impact of human activities on hydrogeology. However, at the same time, we can look at this knowledge with a lens that can be applied at a small and decentralized scale for practical application. It is with this thought that this article has been written.

Introduction

The water supply situation today is very different from 100, 50, or even 25 years ago. India faces challenges of water stress, constituting 16% of the world population but only 4% of the freshwater resources.

With rapid urbanization, cities/towns rely heavily on the cost-intensive long-distance water supplies to meet the widening water demand-supply gap including overexploitation of in-situ groundwater resources while dealing with declining infrastructures. Furthermore, urbanization disrupts the natural hydrological cycle as there is a reduction in infiltration and groundwater recharge due to the existence of large impervious areas, removal of shallow aquifer to build multiple basements, thus urban areas face the twin problems of floods during monsoon and shortage of freshwater during non-monsoon months.

India has had a rich tradition of community-based water harvesting. Each region has a different structure for harvesting rain, from Eris in the southern plains of Andhra Pradesh, Karnataka, and Tamilnadu to Jhalaras, kunds and step wells in Thar regions of Gujarat and Rajasthan, Kuls in western Himalaya, Ahar Pynes and Baolis of the Indo-Gangetic Plains, Zabo, and Virdas in Northeast regions.  This long history of water structures has long been forgotten and has been dumped with garbage or closed off. However, there is a need to reimagine rainwater harvesting, groundwater, open wells, and their relevance in contemporary times.

The solution, therefore, lies in decentralized rainwater harvesting, which is increasingly being turned to as it offers an alternative, affordable, reliable, and sustainable water source in the face of increasing water shortages. Rainwater harvesting can be done using two methods: storing water for direct use or recharging groundwater.

Know your rainfall

Rainfall statistics for the areas is of paramount importance to understanding rainwater harvesting norms. Information on average annual rainfall quantity, distribution across months and rainfall intensity is crucial. Rainfall quantity will decide the potential for rainwater harvesting from any surface i.e., a product of total rainfall and the surface area of collection

Weather Monitoring Stations & Telemetric Rain Gauges

With the concept of “Measure to Manage”, Karnataka State Natural Disaster Monitoring Centre (KSNDMC) has installed 930 weather monitoring stations at Hobli level which captures the 4 major parameters – Temperature, Relative Humidity, Wind Direction, and Wind Speed, and 6500 telemetric rain gauges for monitoring rainfall data. The weather forecasts are made by ISRO and with the Ground level data provided by KSNDMC to ISRO every day, it is possible to get more accurate and reliable predictions.

The near-real-time data collection, report generation, and dissemination have been helping the State Government in planning and executing disaster management and mitigation plans at the micro-level.

Know your geology

Geology plays an important role in the occurrence of water within a watershed. Water availability is governed by the rock types occurring both at the surface and within the subsurface and the extent of weathering and fracturing of the rocks. India has highly diversified hydrogeologic characteristics. There are six extensively documented groundwater typologies across India i.e. mountain systems, alluvial (unconsolidated) systems, sedimentary (soft) systems, sedimentary (hard) systems, volcanic systems, and crystalline (basement) systems (CGWB ). Based on local geology, one can understand the best recharge strategy and the most appropriate recharge tool/structure for the context.

Storing rooftop rainwater for domestic use 
When rainwater is a supplemental or primary source of water for domestic use, then designing for storage is essential. Rainwater harvesting systems will have the following 5 basic components: Catchment area including building roofs and paved areas, Gutters, Downtake pipes, Filters, First flush devices, Storage tanks/ponds and Delivery systems till the point of end-use.

Calculating storage size depends on rainfall pattern, rainfall intensity, catchment area, the total volume of daily usage, budget, and space availability. Ideally, in areas where there is severe water scarcity, there may be a need to harvest and store all the rainwater, but this may be inefficient and therefore can be decided based on the consumption needs. For instance, if 1000mm of rain is falling on a 100sqm catchment, for which you would need 10 lakh litre storage, but this is inefficient. Therefore, an optimal size of a storage tank can be arrived at based on the calculation of daily water consumption, which can be correlated with the total harvestable rainfall. If rainwater is immediately used after collection, more water can be harvested annually for a relatively smaller storage size. 

The stored water should have a point-of-use treatment before end-use. For example, appropriate measures should be taken to ensure it meets the drinking water quality standards if it is to be used for drinking purposes. 

Integrating rainwater into groundwater management 
Groundwater is far more significant in the water-supply of cities and towns but is widely not appreciated, as it is an ‘invisible resource’ connecting various urban infrastructures. Unaccounted groundwater in urban areas exceeds 50% in 28 Indian cities (CGWB, 2011). While some legislation exists that directly or indirectly seeks to help manage groundwater, the enforcement has been weak and a very big barrier. Given the nature of groundwater development and use, for it to reach a scale that can have an impact for the city as a whole, all users and stakeholders need to become part of the solution and make groundwater a community resource. 

Outlined below are a series of things to know about the same:

Groundwater recharge

The percolation of excess rainwater through an infiltration system to the subsurface is called ‘Artificial Groundwater Recharge’. The runoff water collected from rooftops and surface water can artificially recharge and augment the depleting groundwater resources, especially in the urban areas, where the natural recharge has diminished considerably. As a thumb rule, it is important to understand the water resources within the city and at what depths these are found, which can then be taken as a baseline to understand the best recharge strategies.

There are different types of recharge structures – a) Recharge pits; b) Recharge trenches; c) Recharge through dry or operational dug wells; d) Recharge through abandoned/existing tube wells; and e) Recharge wells, etc.


Recharge rate tests
A recharge rate test is conducted to assess the recharge rate of an aquifer i.e. to see how quickly water percolates into the ground. In this test, a known quantity of water is pumped into the well/s being tested, and the time taken for it to percolate into the ground is recorded. Measurements are taken of the depth of the water every minute for the first 10 minutes, then after 15 minutes, 30 minutes, one hour, two hours, and so on. From these measurements, the recharge rate of the well/s can be calculated, which helps us understand the recharge rate of the shallow aquifer in that particular area. The more wells that are tested in an area, the better our understanding of that aquifer.

Million recharge wells for Bengaluru Biome is campaigning “A million recharge wells”: Reviving our responsibility for groundwater. The initiative aims at striking a balance between groundwater extracted and recharged, by digging 10 lakh (1 million) recharge wells across Bengaluru City. The explicit objective of the intervention is to increase the groundwater table in the city while providing livelihoods to the local community of traditional well-diggers (called Mannu Vaddars) in Karnataka. The implicit objective is to build a water culture in the city, where people value water availability, water structures, and also take responsibility for managing groundwater collectively. A recharge well is basically a hole in the ground into which the rainwater runoff can be directed, such that it percolates into the ground, augmenting the water table. The recharge well can be a powerful tool and symbol for reviving our relationship with groundwater as it reconnects us to our open well heritage; it reminds us that unless we fill our aquifers up, we will not be able to extract; and that we cannot extract limitlessly. It also teaches us that groundwater is not anyone’s private property, but a common pool resource.

 

Mapping the aquifers underneath our city through participatory approaches

A city or town should be aligned to all sources of knowledge – often this information does not only come from formal institutions such as hydrogeologists, civil engineering departments, water managing authorities, etc but also from the residents, traditional well-diggers, borewell diggers, etc, who also have an understanding of the local aquifer and geology. Therefore, evolving a participatory approach towards groundwater mapping, with participation from institutions, schools, etc who can help with mapping is useful.

As a result of this, the recharge of aquifers is managed bottom-up, with each citizen also taking responsibility for managing groundwater, either by documenting it or by digging a recharge well. People also begin to understand that they might not directly benefit from recharge wells, but if everyone recharges, the entire community benefits. 

Outreach and communication 
To promote RWH in the city, creating awareness regarding the importance of rainwater harvesting, both for immediate uses and also for sustaining the water table in the long run, is essential. There is a need to shift the initiative from institutional endeavors and make it into a mass movement. There has to be an investment in communicating the city’s problems, the existence of laws and legislations and how the law attempts to address this problem, and therefore the role of citizens to implement the law and be part of the solution.

As awareness of the issue increases, more people begin to understand the ecological flows that surround us, and what they can do to protect these systems. It also inculcates a feeling of giving back and emphasizes the importance of doing so.

[1] http://www.ide-india.org/content/water-india-facts
12] http://www.rainwaterharvesting.org/rural/Traditional3.htm#apat
[3] http://cgwb.gov.in/documents/papers/incidpapers/Paper%201-B.M.Jha.pdf

www.urbanwaters.in Community platforms that demonstrate RWH are useful for understanding the overall scenario. www.Urbanwaters.in web space seeks to inform, guide and provide any and all resources to all of us to make us water literate, solve our individual or community water problems and act responsibly by taking care of our common urban water resources. It seeks to help make us a part of the solution rather than being a part of the problem.