Search

Browse

• Communities
• Authors
• Year
• Titles
• Subjects

My Space

• Login

Comparative study of planted and unplanted sludge treatment wetlands under different sludge loading rates

Fouska Virginia

Full record

---

Summary

In this thesis, a comparative study was conducted on the performance of planted and unplanted artificial wetlands for sludge dewatering under different loading rates. Six vertical flow constructed wetlands were built for the experiment, which took place in the outdoor area of the Chania Wastewater Treatment Plant. Specifically, two of the units were unplanted (control), while the remaining four were planted with *Phragmites australis* (common reed). Half of the units had a solids loading rate of 60 kg/TS/year, while the other half had 80 kg/TS/year. All tanks had the same dimensions (100 cm × 120 cm × 116 cm) and were filled with river-sourced gravel of various granulometries, ranging from coarse aggregates to fine gravel.Regarding operation, primary effluent was applied for 20 days to allow plant adaptation, followed by secondary sludge supplied from the treatment plant. Each tank received sludge based on its assigned solids loading rate, while the irrigation frequency was adjusted according to the tank’s needs. The experiment lasted for 8 months in total. Analyses of influent and effluent focused on parameters such as BOD5, COD, TSS, NH4+- N, NΟ3- - N, TP, ΡΟ43—Ρ, EC, and pH. For the dehydrated solids layer on the surface of the units, additional analyses were conducted for TS, VS, as well as metals and metalloids.The results focus on the residual sludge of units P60A, P60B, C60, P80A, P80B, and C80. The final residual sludge thickness at the end of the experiment is as follows: 0.05 m, 0.055 m, 0.105 m, 0.14 m, 0.145 m, and 0.165 m. The corresponding sludge volume reduction percentages are: 97.5%, 97.2%, 94.7%, 94.7%, 94.5%, and 93.7%. The final TS% values are: 46.35%, 48.77%, 8.71%, 13.22%, 22.55%, and 9.31%. The VS% values are: 77.75%, 78.78%, 77.62%, 77.25%, 75.30%, and 77.17%. Units P60A and P60B were the most successful in terms of dewatering and had the highest total solids content. Additionally, regarding the metal and metalloid concentrations, all pilot units showed values significantly lower than the established limits for sludge application in agriculture. Regarding the chemical characteristics of the residual sludge from units P60A, P60B, C60, P80A, P80B, and C80, the average ammonium concentrations were: 0.39 g/kg, 1.03 g/kg, 0.19 g/kg, 0.81 g/kg, 3.13 g/kg, and 1.22 g/kg. The average nitrate (NO₃⁻-N) concentrations were: 9.30 g/kg, 4.32 g/kg, 24.85 g/kg, 23.0 g/kg, 21.49 g/kg, and 24.81 g/kg. The average total phosphorus (TP) concentrations measured were: 5.42 g/kg, 6.90 g/kg, 10.04 g/kg, 11.02 g/kg, 9.94 g/kg, and 12.93 g/kg. Finally, all units, regardless of loading rate, exhibited similar behavior with comparable plant heights.

Available Files

Services