Use of Commercial Plant Species in a Hydroponic System to Treat Domestic Wastewaters

Abstract

The objectives in this work were to investigate a conceptual layout for an inexpensive and simple system that would treat primary municipal wastewater to discharge standards. A commercial hydroponic system was adapted for this study and the wastewater was used to irrigate wooly digitalis (Digitalis lanata Ehrh.) and foxglove (Digitalis purpurea L.). These plants are medicinal and produce cardenolide compounds. Influent and effluent samples were collected once a month for six months and analyzed to determine the various parameters relating to water quality. The legal discharge levels for total suspended solids (SS), biochemical oxygen demand (BOD5), and chemical oxygen demand (COD) were reached for the two tested plants after 48 h of wastewater treatment; the removal was 82, 93, and 79%, respectively, for wooly digitalis and 92, 92, and 84%, respectively, for foxglove. Similar results were obtained during a 6-mo period although the sewage composition varied widely. The system tended to be unable to remove N and P to concentrations below regulated levels. Compared with the nutrient solution composition, the wastewater was more concentrated in Na+ and Cl- and less in N, K+, and Ca2+. These variations can lead to the decline of wooly digitalis plants. Foxglove developed a significant root system to increase mineral absorption wastewater being used as the unique nutritive source. After 10 wk all the wooly digitalis seedlings were dead. Despite this fact, however, the root system remained in place for a significant time (< 4 mo), thus continuing to filter wastewater and to be used as a bacterial support thus making it possible to have a security period to replace the dead plants.

Evaluation ofPopulusandSalixContinuously Irrigated with Landfill Leachate I. Genotype-Specific Elemental Phytoremediation

“…This may have been due to a sensitivity of this clone to salinity stress in the stems (Wang et al, 2002). In addition to being important for cellular division, nitrate assimilation, and being a cofactor for some enzymes (Vaillant et al, 2004), Ca contributes to membrane integrity and, thus, is a structural component for plants (Redfield et al, 2003). These results corroborated those of Zalesny and Bauer (), where root dry mass of SX61 was significantly less with leachate irrigation than water.…”

“…Similar salinity stress was observed for stem Na concentration, where all clones, regardless of genus, responded better to water than leachate. These results are intuitive, given that the Na concentration in our leachate (142 mg L −1 ) was 31 times that of a standard nutrient solution (4.6 mg L −1 ) (Vaillant et al, 2004) and that Ca availability should be greater for alkaline conditions such as with the water treatment (pH 8.4) compared with the acidic leachate irrigation (pH 6.3) (Foth, 1990). However, Populus clones Beaupré (63.4 mg Na kg −1 ) and Trichobel (70.7 mg Na kg −1 ) did not exhibit similar salinity stress (Moffat et al, 2001), despite nearly-identical stem Na levels to the mean of the current study (75.27 ± 8.12 mg kg −1 ).…”

Use of Barley for the Purification of Aquaculture Wastewater in a Hydroponics System

“…Bouzoun [30] evaluated the feasibility of utilizing hydroponically grown reed carnarygrass to reduce the pollution load of a primary treated municipal wastewater and reported an average NH 4 + -N reduction in the wastewater of 34% over a 5 month period. Vaillant et al [47] evaluated the effectiveness of Datura innoxia plants for domestic wastewater purification and reported NH 4 + -N reductions in the effluent of 93% after 48 hrs of treatment. MacKenzie [17] examined the use of a hydroponics system planted with wheat for nutrient removal from an anaerobically digested dairy manure and reported NH 4 + -N reductions ranging from 80.4 to 85.8%, from 64.5 to 72.0% and from 57.4 to 69.8% after 21 days of growth for wastewater applications rates of 300, 600 and 900 mL/compartment/day, respectively.…”

“…Forms of inorganic nitrogen that are associated with particulate matter may be removed from waste streams by sedimentation and filtration/interception by the root mats of plants [33] . Ammonium (NH 4 + ) is one of the major sources of inorganic nitrogen taken up by the roots of higher plants [47] . It may be assimilated by microorganisms and converted back into organic matter or may be removed from waste streams through the process of nitrification [39] .…”

“…Several mechanisms are responsible for the removal of NO 3 --N from the wastewater. NO 3 --N is the preferred form of inorganic nitrogen taken up by the roots of higher plants [47] . It may also be assimilated by microorganisms in the water column or by biofilms associated with the root mats of plants [39] .…”