Reed Bed: A Green Waste Water Treatment Option

Pallavi Kalale's picture
Pallavi Kalale
Architect
July 23, 2013

Looking for a better way to manage your wastewater? Consider constructing a reed bed for a natural, green alternative.

This reed bed treats graywater, then reuses the effluent to irrigate other plants.
This reed bed treats graywater, then reuses the effluent to irrigate other plants.
Credit: Sustainable Sanitation via Flickr

While providing habitats for wildlife, reed beds are becoming the popular and sustainable choice for wastewater and sludge management. Reed bed systems are an effective, sustainable and low maintenance method of sewage treatment. While aesthetically pleasing to the eye, it requires no electricity and, once matured, provides an ecological habitat for a wide range of species. With the help of common reed plants, reed beds drain all wastewater and pollutants from solids while artificial reed beds are used as a method of removing pollutants from greywater.

The proper utilization and disposal of sludge is one of the most critical issues faced by wastewater treatment plants. The most important part of sludge management is to retain the nutrients in the sludge. Reed beds are an alternate method for sludge treatment.

Green water treatment technologies, such as reed beds, have been applied for the treatment of domestic effluents in rural communities. These small volumes of waste discharged into ponds prove that conventional systems are not as cost-effective. Landfill costs are increasing, while incineration permits are expensive and difficult to obtain. However, reed beds which are widely used throughout Europe, Asia, Australia, and the United States, provide long-term storage and volume reduction of biosolids-- organic matter recycled from sewage-- to mitigate these concerns.

How Do Reed Beds Work?

The Common Reeds (Phragmites Australis) transfer oxygen directly from their root systems and through their stems. The root systems are met by a multitude of micro-organisms with areas of varying oxygen levels. As a result, the wastewater stored in reed beds is treated and recycled. The reed bed filters the water just as the conventional biological filter bed systems of sewage treatment plants.

Earlier reed bed sewage treatment systems used horizontal flow reed beds, where the liquid flows horizontally. However, all sewage treatment should be efficient to shorten the waste maturation timetable. A few ways to speed up maturation include partially pre-growing the reed plants or creating a vertical reed bed system.

Credit: The Water and Carbon Group

 

Types of Reed Beds

Horizontal Flow (HF Systems): As mentioned prior, the more traditional reed beds are horizontal, allowing waste to travel through the reed’s root zone. Once passing through, the waste finds itself on the opposite side of the reed bed.

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Vertical flow (VF Systems): Another option is vertical reed beds, in which the waste starts at the top of the bed and drains through at the bottom. Each time waste travels through this sludge management system, it oxygenates the reed bed. Because of these increased oxygen levels, VF systems are more effective than HF systems when eliminating ammonia. VF systems take up less space and, therefore, can break down waste on a much higher scale.

NOTE: Both horizontal and vertical flowing reed beds can be installed in the same location for maximum efficiency.

Pros and Cons of Reed Beds

Pros

  • minimizes solids
  • reduces water content
  • minimal day-to-day operation
  • no requirement of highly trained operators
  • mechanical and electrical equipment are needed
  • pumping not necessary as the system works on gravity
  • provides sufficient storage time to stabilize biosolids prior to disposal
  • blowers to aerate is not required as the aeration is facilitated by reeds

Cons

  • Large land area is required for correct treatment

Note: Reed beds are subject to Environment Agency Permitting guidelines, so be sure to review them before constructing the reed bed.

While these systems need a large area of land to be fully utilized, the benefits and effectiveness of the treatment outweigh the cons. 

The Effectiveness of Reed Beds

According to the U.S. National Library of Medicine National Institutes of Health, a study was conducted from April 2008 to June 2010 where six reed beds were examined. For about 1-5 days, the researchers loaded the reed beds with sludge and allowed the beds to rest for about 35-55 days. The study’s results reveal the amazing benefits of utilizing reed beds.

Poplar Newsletter Sign UpFor example, the waste takes the place of fertilizer in promoting the growth of the reeds. The waste proved to be treatable with the help of the reed plants.

The waste in its dry solid form was concentrated roughly 200 times in the dewatering phase. Following the draining, the waste was 30-40 percent solid and efficiently broken down. From this experiment, the researchers found that 99 percent of the sludge volume was filtered out as water with a turbidity--level of cloudiness-- of below 5 NTU.

In conclusion, taking advantage of the reed bed is the best, most sustainable option. What if you could turn waste into fertilizer or even drinking water? 

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