Our competition runner-up reports on the challenges faced by India's most marginalised people. Often forced to work as manual scavengers clearing sewers and latrines, Dalits must struggle against the legacy of generations of prejudice This trip was hosted by WaterAid

In the early afternoon heat 65-year-old Uma Devi quietly walks the lanes of a crowded slum in Patna, capital of north India's populous Bihar state. A small, battered tin bowl hangs from her fingertips and a blue plastic bucket balances securely on her head as she makes her way through the narrow streets.

She stops in the shadows of a brick house, squats on her haunches and lifts a frayed yellow canvas covering a hole brimming with human excrement. With a practised hand she rhythmically transfers bowlful after bowlful of waste into her bucket, quickly emptying the latrine before silently moving on.

Uma is a Dalit, one of the 201 million Indians who fall outside the rigid, hierarchical caste system that remains deeply entrenched in society. More than six decades after caste-based discrimination was outlawed in India, Dalits are often still seen as "untouchable" and "impure", and continue to be relegated to a life of exclusion and exploitation.

Occupying the lowest rung within the Dalit community are manual scavengers like Uma who scrape an existence cleaning dry latrines – toilets that are still not connected to the sewage network. With a tin plate and broom they load human excrement into buckets or baskets, which are then carried on their heads to be emptied on strips of reeking wasteland several kilometres away.

"The manual carrying of human faeces is not a form of employment, but a custom integrally related to the caste system, based on inequality and injustice," says Ashif Shaikh, convener of the Rashtriya Garima Abhiyan (RGA), the National Campaign for Dignity and Eradication of Manual Scavenging. "It is one of the most prominent forms of discrimination against Dalits, and is central to the violation of their human rights."

Manual scavengers are India's hidden communities, crammed into slums and largely forgotten as the country marches forward as the world's largest democracy. They are shunned by society, often banned from entering temples or accessing the same water pumps as higher castes – rules that are enforced by verbal abuse and violence.

It is a fate inherited over generations, cemented at birth or by marriage. Uma has been a manual scavenger for more than 50 years, beginning just months after she married at 11 years old. "The first time was a very bad experience," she says, her steely eyes fixed on the floor. "I had fatigue for six months, I could not eat properly. The waste used to spill on my body and clothes. But I had no other option because I had to provide for my family. Gradually I reconciled that I would have to do it."

Today, activists estimate there are 300,000 manual scavengers in India, despite repeated high-level commitments to stamp out the practice. In 1993 the Indian government outlawed the construction of dry latrines and the employment of manual scavengers. But implementation has been poor, and there remains a huge gap between what is written in legislation and progress on the ground.

The latest census in 2011 showed there are still around 800,000 Indian households with dry latrines that are cleaned manually. To date, nobody has been prosecuted for employing manual scavengers, and the state-owned Indian Railways continues to be one of the largest employers of manual scavengers.

"India has failed to prioritise access to sanitation, trapping people in poverty and perpetuating social oppression," explains KJ Rajeev, WaterAid India's regional manager. "Manual scavenging is a prime example of how the poorest, most excluded people in the country are hit hardest by this sanitation crisis."

Internalised discrimination

The conversion of dry latrines to flush toilets is seen as a key step towards the eradication of manual scavenging in India, but there is also widespread recognition that manual scavengers need support in seeking alternative livelihoods. "There is a degree of internalisation that takes place [among manual scavengers]," explains Rikke Nöhrlind, co-ordinator of the International Dalit Solidarity Network. "They have seen their community do this for decades, and they think that this is how it has to be as they don't have any other possibilities."

Government efforts to provide manual scavengers with loans to set up new businesses have often failed to reach the slum communities, where few of the illiterate manual scavengers know help is available. A 2011 report by the RGA also exposed widespread corruption within the scheme, revealing that in some states up to three-quarters of those who received financial assistance were not actually involved in manual scavenging.

Even if manual scavengers receive loans, success is not always guaranteed. Many fall back into manual scavenging as financial assistance alone does little to address the deeply ingrained discrimination they face. Uma has tried to leave manual scavenging before, once accessing a government loan to start a business selling pakori snacks. "Because I'm a manual scavenger nobody from the other castes would buy from my hands, so whatever products I made got wasted," she says. "The stigma of being a manual scavenger was very heavy and I could not establish myself as somebody who could sell food."

To bridge the gap, activists and charities are providing manual scavengers with the advice and support they need to make the first steps to liberation, and persuading those who have previously failed to leave manual scavenging to find the determination to try again. Crucially, they are also galvanising these people to make a public stand against the practice, organising mass demonstrations where manual scavengers show their refusal to engage in the practice by burning the baskets they use to carry excrement.

The very visible protest of a once invisible community sends a clear message that caste-based discrimination should not be tolerated, and is resulting in changes. In September, India's parliament passed a long-awaited bill that many see as the first step towards closing the loopholes of previous legislation, and providing tougher sanctions for those who violate the law.

"I wouldn't say there is optimism, but I would perhaps say there is hope," says Tom Palakudiyil, WaterAid's head of South Asia. "Manual scavenging has been able to continue because of the ability of the majority population to block it out of their minds. But more and more, indignation is growing and more importantly fewer and fewer manual scavengers are now willing to do this work."

Despite her own setback, Uma is determined that she will not be a manual scavenger for the rest of her life. "I want to start up a new business," she says. "I am hopeful that one day this will end."