Kaba, Tasissa (PhD)Ali, Solomon2018-06-272023-11-082018-06-272023-11-082013-03http://etd.aau.edu.et/handle/123456789/3864Environmental pollution resulting from the discharge of untreated industrial effluents has been putting serious risks on the survivability and perpetuation of all living things including human beings for the past few years. From the various treatment methods natural means of treating industrial wastewater have been exercised in many parts of the world for they are environmentally permissible and help to keep its natural values. Among those natural ways of treating wastewater constructed wetlands have been utilized for the past few decades. In this research three horizontal subsurface flow constructed wetlands (HSSFCWs) have been used for the treatment of dairy wastewater discharged from Ada milk factory. The first HSSFCW was kept as control with only gravel and the rest two HSSFCWs were planted with widely used emergent plant species, Typha latifolia and Scirpus lacustris. The wetlands flow rate was adjusted to 25 L/d and as hydraulic retention time (HRT) 8 days was used for three replicates of the experiments. After laboratory investigations were carried out it was found that the wetland planted with Scirpus lacustris showed better capacity in removing pollutants from the dairy wastewater than the wetland planted with Typha latifolia. The average removal efficiencies of the wetland planted with Scirpus lacustris and the unplanted wetland were found as follows, respectively. BOD (84.2%, 65.2%), COD (84.4%, 68.2%), TN (43.4%, 22.8%), NH4+-N (84.2%, 59.2%), NO3_N (97.5%,88.7%), TSS (65%,70%,),VSS(32%,43%), TP (53.8%,27%), OP (80.7%,75.2%), FOG (95.3%,93%), TCa (39%,21.8%) and TC (89.7%,69.3%). Besides their importance in wastewater treatment, these emergent plants have versatile uses among these their medicinal and dietary values were widely recorded. Thus, it is environmentally advisable mechanism to utilize constructed wetlands for wastewater treatment. From laboratory investigations it was found that BOD, TN, NH4+-N, NO3--N, TP and PO43--P are the main factors for the pollution of the Dairy wastewater. Keywords: Constructed wetland, Scirpuslacustris, Typhalatifolia, dairy wastewaterenConstructed wetlandScirpuslacustriTyphalatifoliadairy wastewaterThesis