Water is a precious resource, especially in emerging markets. Siemens' facility in Kalwa, India, recycles its wastewater with one of the environmental initiatives that won the Vasundhara Award 2011 - a sewage treatment system that uses plants.
Plants handle water treatment at a Siemens facility in Kalwa, India, where 3,000 employees manufacture switchgear and transformers.
Customized Water Recycling
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Anyone paying a visit to the new sewage treatment plant at the Kalwa factory near Mumbai will think they have entered an oasis. Between production halls and areas covered with asphalt lies a small collection tank containing treated water — sparkling, turquoise-colored and clear as glass. Next to it is a gravel-filled basin in which meter-high reeds grow along with plants bearing red blossoms. “On an area of about 1,000 square meters, we recycle all of the wastewater from our four subplants, as well as from the administrative building,” says Jeevan Rao, who heads the Safety and Environmental department for Siemens Cluster South Asia. The new sewage treatment plant with its artificial wetland is an important part of Siemens’ environmental initiative, which was honored with the prestigious Vasundhara Award 2011 in June. The Vasundhara Award is the most important environmental prize of the southern Indian state of Maharashtra.
The water recycling system used at the Kalwa factory functions like a swamp. Instead of relying on advanced technology, the system employs an ecosystem of plants and microorganisms that eliminate harmful substances from the wastewater. The system features a cascade of 32 basins that treat the water mechanically as well as biologically. For example, the gravel holds back particles suspended in the water, while the plants produce oxygen and their roots ensure that the gravel bed is well ventilated. Bacteria break down organic substances — such as scraps of food or dirt from hand washing — into carbon dioxide and water. And nitrogen compounds such as proteins or urea are ultimately converted into harmless nitrogen gas. At the end of the cleaning facility, which is more than 90 meters long, the treated water is so clean that even mosquitoes aren’t interested in it any longer. A system of pipes then channels the water to the Siemens administrative building, and to the garden facilities and rest rooms, where the cycle begins anew.
Natural Advantages. “Besides being effective, inexpensive, and simple to maintain, the facility just looks idyllic,” says Rajiv Agaskar, Sustainability Officer for Siemens Real Estate India. “It enables us to save up to 12 million liters of water per year.” In addition, natural water recycling reduces the facility’s fresh water costs by up to €4,500 annually. What’s more, according to Agaskar, the facility cost less to build than a high-tech counterpart. The only technology the system needs is pumps and flow-rate meters, and it doesn’t have to be continuously monitored, as is the case with conventional sewage treatment plants.
Given all these advantages, it’s no surprise that sewage treatment plants equipped with artificial wetlands are becoming more popular worldwide. Their only drawback is that they take up a lot of space. A city of 100,000 inhabitants would need a facility almost as big as 60 soccer fields. And the facility has no control system, making it unsuitable for wastewater whose composition fluctuates greatly.
The newly constructed wetland in Kalwa recycles two types of wastewater, which are first separately collected and pre-treated. Most of this water comes from toilets, sinks, and the canteen. It is channeled into a precipitation tank, where solid substances that are sometimes very smelly can settle. The wastewater from the Siemens production halls primarily contains finely distributed oil droplets, which are pretreated separately before the water is sent to the wetland.
“All of the pre-cleaned water then flows through the wetland,” says Agaskar. The facility’s concrete basins in varied sizes are more than one meter deep and have a downward slope. Barriers cause the water to flow into a basin at the top and flow out again at the bottom. “Our facility purifies the water horizontally and vertically, achieving 95 percent efficiency — better than the 90 percent efficiency achieved by many conventional treatment plants,” Agaskar says.
Although India is home to 16 percent of the world’s population, the country has only four percent of the planet’s water reserves. “Groundwater levels are dropping by four centimeters every year,” says Agaskar. Climate change will probably make this even worse. Artificial wetlands alone will not be able to solve the problem. But as Agaskar and Rao say, “Every component is important.”