Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6302614 | Ecological Engineering | 2013 | 10 Pages |
A hybrid sub-surface constructed wetland (CW) system consisting of 2 gravel filled vertical sub-surface (VFa & VFb) beds, each 160 m2 in size planted with Phragmites australis and a sand filled horizontal sub-surface (HF) bed, 336 m2 in size, planted with rice was operated from 2007 to 2010 for treating milking parlor waste water in Hokkaido, Japan. Hybrid CW system received huge fluctuations in average yearly inlet loads for TSS (526.0-1259 mg Lâ1 & 2.7-9.0 g mâ2 dâ1), BOD5 (1,080-2,114 mg Lâ1 & 8.4-14.4 g mâ2 dâ1), COD(1,962-7,085 mg Lâ1 & 14.5-50.0 g mâ2 dâ1), TN (116.0-243.0 mg Lâ1 & 0.8-1.6 g mâ2 dâ1), NH4-N (54.0-90.0 mg Lâ1 & 0.40-0.64 g mâ2 dâ1), TC (1,022-2,215 mg Lâ1 & 6.0-15.1 g mâ2 dâ1), TP (15.3-41.7 mg Lâ1 & 0.11-0.28 g mâ2 dâ1) during study period. Average yearly purification and removal rates were least fluctuated for TSS (95.7-99.4%); moderately for BOD5 (86.1-95.7%), COD(87.5-96.1%) and TC (79.5-91.3%); highly for TN (72.6-90.6%), NH4-N (62.9-85.3%) and TP (64.8-87.2%). A sharp decrease in TP purification and removal rates were observed in 2008 due to sharp decrease in influent TP concentration in 2008 compared to 2007. OTR values for VF(a), VF(b), HF bed and total system were observed as 21.7, 19.3, 4.8 and 12.3 g O2 mâ2 dâ1 respectively. Average k value of hybrid CW system for BOD5, TN, NH4-N and TP during study period were 7.0 ± 1.8, 7.4 ± 3.3, 5.6 ± 4.1 and 4.9 ± 2.0 m yrâ1 respectively.Average concentration of TSS, TP, TN and NH4-N in the final effluent for all years were below the discharge limit value of: 150 mg Lâ1 for TSS; 8 mg Lâ1 for TP, 60 mg Lâ1 for TN and NH4-N. However, average BOD5 and COD concentrations could not meet the discharge limit value of 120 mg Lâ1 during 2007 and 2008.