Vegetated
Sand
Bed
VSB
RECYCLE WATER
Vegetated Sand Beds are man-made treatment systems designed to emulate the biological capability of natural wetland processes to break down and remove contaminants from wastewater. Each VSB built by NEWS is a sub-surface flow system, has an impermeable liner, growth media, drains, and plants. The wastewater being treated is hydraulically controlled in a way that maintains a water table just below the surface of the growth media. As such the plants grow hydroponically in the media while the wastewater slowly passes through the system.
ā
ā
Reed
Bed
Technology
RB
SUSTAINABLE
Reed Beds are comparable to a conventional sludge drying bed planted with reeds (Phragmites australis). Unlike a conventional bed, Reed Beds do not have to be scraped off before the next layer of sludge is added. Sludge is applied to the Reed Bed every two weeks year-round for 10-15 years. Over the life-cycle of a Reed Bed, the initial sludge volume will be reduced 95% to 98%, through drainage, evapo-transpiration, plant uptake, and microbial decomposition. The final product is a well-decomposed, stabilized, humus-like residue suitable for land application.
ā
Research
Ammonium
Ammonia
VSB POTENTIAL
ā
Nitrogen compounds are a concern in wastewater due to their role in eutrophication, effect on oxygen levels of receiving waters, and toxicity to vertebrate and invertebrate species.
The limitations of conventional technology for economically treating nutrients is an issue in many regions of the world. Additionally, the inability to treat complex organics such as synthetic hormones, antibiotics, and other pharmaceuticals and personal care products (PPCPs) to levels which have no perceivable effect on the environment is also of international concern. To this end, NEWS is dedicated to ongoing research in the treatment of all contaminants in water.
ā
Research on the transformations of various nitrogen compounds ocurring in NEWS wetland VSB cells was published in Water Environment Research (Vol. 82, p. 592, 2010). This study indicated 100% removal of biochemical oxygen demand (BOD) and 99.0% removal of ammonium (NH4+). The wetland system, located in Highland, New York , treats primary domestic wastewater and was subject to a New York State SPDES discharge permit. This top-loading, vertical-flow, submerged-bed constructed wetland system (U.S. patent number 7,510,649; Lavigne, 2009) consists of four beds operating in series. Influent and effluent samples from each of the four treatmet units were analyzed for BOD, ammonium-nitrogen (NH4+-N), nitrate-nitrogen (NO32--N), and nitrite-nitrogen (NO22--N). During the study, mean influent wastewater concentrations were 170.8, 3.1, and 0.015 mg/L for ammonium, nitrate, and nitrite, respectively. Mean effluent concentrations were 1.9, 4.2 and 0.002 mg/L for ammonium, nitrate, and nitrite, respectively.
Discharge from VSBs can occur through evapotranspiration, infiltration, irrigation, or reuse of the treated water. These mechanisms allow for treated water to re-enter the water cycle as well as recharge the groundwater table which is being depleted by anthropogenic activity in the U.S.A. and many parts of the world.
Reed Beds have been used successfully to treat sludge from food processing facilities, wastewater treatment plants, animal shelters, industrial operations, and many other sources. For wastewater treatment facilities looking to cut expenses and implement sustainable practices, convert existing sand drying beds or build new RBs and only have to dispose of accumulated sludge every 10-15 years.
In 2011 the New England Regional Turffgrass Foundation financed an experimental VSB project to demonstrate the effectiveness of treating water used to wash turfgrass equipment for reuse, (see Golfdom, Feb 2017). To date, data has been collected for nitrogen compounds (ammonium and nitrate), total phosphorus, and chlorothalonil (a commonly used turfgrass fungicide).
ā
This research was done in the format for treating and recycling water at golf courses, however this technology has many other applications such as farming operations and municipal wastewater treatment especially where elevated nitrogen levels are an issue.
VSB treatment is accomplished by the presence of aerobic and anaerobic zones and therefore aerobic and anaerobic microorganisms, sieving, cation exchange, adsorption, and plant uptake among other processes. Each system is designed to treat a specific wastewater and to meet the needs of the site, manipulating the conditions to accomplish optimal treatment.