Utilizing green infrastructure in water management and water treatment systems can help companies achieve economic and environmental benefits. And yet these ecosystem-based management approaches haven’t gone mainstream.
Green infrastructure employs elements of natural systems such as reed beds that treat industrial wastewater, green roofs and permeable pavements that allow water to infiltrate, be filtered and replenish groundwater supplies. Traditional gray infrastructure is man-made.
The Case for Green Infrastructure recommends that green infrastructure become part of the standard toolkit for engineers. In the white paper, Dow Chemical, Shell, Swiss Re and Unilever, working with The Nature Conservancy, concluded that hybrid approaches, utilizing a combination of green and gray infrastructure, may provide an optimum solution to a variety of shocks and improve the overall business resilience.
For example, Union Carbide, a Dow subsidiary, saved energy and reduced capital and operational expenses by using constructed wetlands to treat wastewater near Seadrift, Texas.
The green infrastructure, which was implemented in half the expected time for the gray infrastructure alternative, was fully operational in 18 months. The capital expense was between $1.2 million and $1.4 million, compared to an expected $40 million for gray infrastructure. The wetlands also require no electric power and very little operations and maintenance support as opposed to the energy-intensive gray infrastructure alternative requiring 24/7 support.
Another example is Petroleum Development Oman, which uses constructed wetlands to treat produced water from oilfields in Oman. The Nimr oilfields, in which Shell is a joint venture partner, produce oil and more than 330,000 m3 of water per day. PDO built the world’s largest commercial wetland, and it treats more than 30 percent (or 95,000 m3 per day) of the total produced water.
Power consumption and CO2 emissions are 98 percent lower than they would have been with the alternative man-made solution. Also, the wetlands provide habitat for fish and hundreds of species of migratory birds.
But while becoming increasingly recognized as solution to water management challenges, barriers to green infrastructure systems still exist, according to Green Infrastructure: Guide for Water Management, a collaborative efforts by the United Nations Environment Programme, UNEP-DHI Partnership – Centre on Water and Environment, International Union for Conservation of Nature, The Nature Conservancy and the World Resources Institute. The guide says one of the main barriers is a lack of awareness about green infrastructure solutions and the associated cost-benefits.
In addition to primary water management benefits — regulatory compliance, water quality regulation and extreme weather and flood mitigation — green infrastructure can generate significant co-benefits, the document says. These include provision of food, recreation and erosion control, as well as cost savings in operations and in avoiding costly investments in new or expanded grey water infrastructure.
Similar to The Nature Conservancy white paper, Green Infrastructure: Guide for Water Management suggests combining tools to develop green and grey infrastructure. It also recommends pilot testing of green infrastructure methodologies and tools and outreach to communicate the benefits to target audiences.
Giulio Boccaletti, global managing director for water at The Nature Conservancy, tells Environmental Leader that green infrastructure lowers water management costs and saves energy in addition to conservation benefits.
He points to the Nairobi Water Fund as an example, The fund, which TNC helped establish, brings together Nairobi’s water utility KenGen, farmers, NGOs and investors to restore the Upper Tana River, which supplies the bulk of the city’s water. The fund will invest $10 million in the area on activities including vegetation buffer zones along riverbanks, agroforestry, terracing of steep and very steep farmlands, reforestation for degraded lands at forest edges, grass buffer strips in farmlands, mitigation of erosion from dirt roads.
Boccaletti says it’s expected to return $21.5 million in benefits over 30 years. It will also provide $3 million annually in increased yields for farmers, an additional $600,000 a year for the water utility as a result of increased power generation and avoided shutdowns and $250,000 in annual savings for Nairobi City Water and Sewerage Company (NCWSC), including through lowering the costs of filtering water and disposing of sludge.
“Srinagar, India, is another case the demonstrates the benefits of natural infrastructure,” Boccaletti says.
The town draws 121 megaliters per day (MLD) from the Sindh River. The upstream contributing area is 1,120 hectares, and 94 percent cropland. Water treatment for the 121 MLD of the town’s water supply could cost about $1.8 million per year.
Assuming a 5 percent reduction in costs from the project’s target 10 percent reduction in sediment and phosphorus, the utility’s willingness to pay for source watershed conservation would be $90,000 per year, Boccaletti says.
Agricultural best management practices (BMPs) would help avoid sediment and phosphorus: 32 hectares of agricultural BMPs would need to be installed to remove 10 percent of sediment and phosphorus, Boccaletti says. “In other words, working on 3 percent of the cropland is sufficient to reduce sediment and phosphorus in the basin by 10 percent.”
Assuming a $360 per hectare per year payment to farmers to follow agricultural BMPs, the utility receives a payment of $12,000, he says: “Such an investment clearly seems like one with a positive return on investment for the utility: the benefits of conservation are almost nine times the costs.”
Photo Credit: green infrastructure via Shutterstock