Office uses artificial wetland to clean its water

A university water quality specialist in North Carolina has the state’s first self contained wastewater treatment system for an office building.

The system uses an artificial wetland to purify 1,200 gallons of sewer water daily from 60 employees and, says its creator, would be of benefit to small communities and buildings in rural areas where conventional wastewater treatment systems are not feasible.

“We think of it as mimicking nature,” said Halford House, creator of the system which is in a renovated school too remote to be within reach of municipal wastewater systems. “Nature has been cleansing water for millions of years, so we figure it’s got the process figured out pretty well.”

The wastewater treatment system has three main components. Firstly, a ‘hill/marsh’ wetland that mimics a set of sand dunes around a marsh, into which wastewater is released automatically every six to eight hours. The water filters through three sand filters (the hills), where sand, microbes and plant roots transform and store potential pollutants. The second component, a wetland designed to flood and drain like a tidal marsh is controlled to influence the flow of nitrogen and phosphorus from the system. Finally, the water is disinfected by ultraviolet light and diverted to a set of greenhouses where tropical plants take up or transform the small concentrations of remaining nutrients. On leaving the greenhouse, the water is treated with chlorine and then reused in the office building.

The treated wastewater is used to flush toilets in the building and to irrigate the lawn and other plants. “It’s clear, it sparkles, and it looks like it’s right out of the tap, but it has nutrients in it, so it’s liquid fertiliser,” said House, explaining that, with the addition of a few minor cleansing steps, the water could be made suitable for drinking. With some alterations, says House, the system could also be maintained inside a building, making it useful to urban environments and in colder northern climates.

Continuing the reuse theme, crushed building brick and decking made from recycled plastic and sawdust are used in the exterior courtyard, and windows from a condemned building were used for the greenhouse.

“There’s no question that it’s enhanced the facility, in addition to making it possible,” said Lyle Estill, president of software distributor EMJ America Inc., who paid to have the building renovated in the mid 1990’s. “Giving a tour of the building is greatly enhanced by the greenhouse and the courtyard. It’s a great place to bring a customer, to bring a client.” In spring 2000, EMJ received a Governor’s Award for Excellence in Waste Reduction from the state’s Department of Environment and Natural Resources, in part for its sponsorship of the water recycling project.

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