Ruiz was the only woman in her class at the National University of Engineering, where she majored in industrial engineering. She later earned an MA in Ecology and Environmental Management from the Ricardo Palma University and a PhD in Chemistry from Ramon Llull University in Barcelona. She started working on health and environmental problems caused by uncollected household waste in Peru when she was a student. When Ruiz started her work in the Cono Norte neighborhood of Lima, 600 metric tonnes of waste were being generated daily, only half of which was collected by the city's collection service. The remainder was left to accumulate in unhygienic heaps, or left along public roads and in vacant lots. This situation existed in other towns throughout Peru, where waste can often be found dumped into rivers, contaminating the drinking water supply. After writing her thesis, Ruiz came up with an idea for a new community-managed system of waste collection that she hoped would serve as a model for urban and rural communities around Peru. In 2001 she founded the group Ciudad Saludable, a social enterprise that aimed to turn waste collection into a profitable business. The group trains local business owners to collect and process the waste, providing employment in a community with a chronically high unemployment rate. Ruiz helped the businesses in their startup phase, charging a monthly fee for the service of about US $1.50, and assisted the new startups with marketing schemes. One marketing campaign employed distribution of gift baskets to families to encourage them to use the services, and to pay for them on time. As of 2014 the group had trained over 300 professionals from Peru, Brazil, Venezuela, Chile and Ecuador, overseeing projects in 20 cities across Peru, employing more than 150 people and providing services to over 3 million residents in Peru. Ruiz was subsequently asked by the Peruvian government to come up with a national plan, and led the creation of the first law in Peru to regulate the activities of waste recyclers. Ruiz and Ciudad Saludable developed a distance education program on waste management, with the Catholic University of Peru, in six versions of the program. They have has organized more than 1,500 waste collectors, creating employment and improving health and living conditions for over 6 million people living in rural and poor urban regions in Bolivia, Brazil, Colombia, Mexico, Peru, Venezuela and India. Ciudad Saludable also established the organization Peru Waste Innovation, a consulting firm specializing in solid waste management, and Healthy Cities International in New York City, which works to replicate the group's model in other countries.
