טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentNesterenko Anastasia
SubjectUse of Aquatic Plants for Treatment of Wastewater Streams
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Mr. Yoram Zimmels (Deceased)


Abstract

The aim of this research was to study the application of Water hyacinth (Eichhornia crassipes) and Water lettuce (Pistia stratiotes) plants for urban sewage treatment. Batch and cascade experiments verified that the plants are capable of decreasing all tested indicators of water quality (BOD, COD, TSS, Turbidity, Ammonia, Phosphorus, and pH) to levels that permit the use of the purified water for irrigation according to the standards of the Israel Ministry of Environmental quality. It was shown that the plants can overcome changes in the feed and still maintain the required levels of the measured water quality indicators. A major effect of treatment with plants was elimination of the disturbing smell from the wastewater, which poses serious problems in various locations throughout the country.

Results obtained in this research show that performance of wastewater treatment with and without plants is always higher when plants are present. Eichhornia and Pistia effectively removed BOD, TSS, and Turbidity from wastewater at 2-4, and Ammonia at 5-8 day residence time (under aerated conditions). Almost complete removal of these water quality parameters was observed in different experimental systems with floating aquatic plants, independently on their initial levels.

Despite the fact that Eichhornia and Pistia are less effective in COD and phosphorus removal, the relatively high reduction percent of these parameters was observed during this research (60-96% for COD and 50-98% for phosphorus).

Results of this research show that aquatic plants are capable of effective pollutants removal from wastewater under initial low levels of the water quality parameters. For example, COD was reduced from 32-36 to 12-13 mg/L O2, BOD5 from 9-10 to 1.3-1.4 mg/L O2, and Ammonia from 9.2-9.6 to 0.2 mg NH4-N/L.

Effect of aeration on wastewater purification by aquatic plants was examined in this work. According to the data observed in the experiments, in the presence of aquatic plants, artificial aeration does not influence the final removal efficiencies of the pollutants, but enhances their removal kinetics. Under the aerated and non-aerated conditions, the same final concentrations of all analyzed parameters were observed, but removal kinetics involved was different.

In this research bacteria removal from the Water hyacinth roots by Ultrasound and sterilized solution was checked. Results show that bacteria removal from plant roots may enhance the performance of aquatic plants in sewage purification systems.

The importance of this research lies in proving the ability to exploit the aquatic macrophytes in removing the various pollutants from wastewater.