Biological Nitrogen Transformation Efficiency in Removing Nitrogen and Improving Water Quality from Zakho Municipal Wastewater in Kurdistan Region/Iraq

Abstract

Samples of municipal waste water was taken and subjected to biological nitrogen transformation (BNT) of ammonification nitrification, and denitrification processes in order to remove the excesses level of harmful nitrogen forms and to improve physio-chemical properties of wastewater. Results revealed that the BNT is efficient in removing all forms of Nitrogen from waste water, especially in end of denitrification process, nitrite reduced about 96% and nitrate reduced to 75%. nitrification process can convert about 17 % to nitrate in one-month period while in the end of denitrifying process this range was elevated to 40 %. Total Kjeldahl nitrogen reduced by ammonification about 17%, and nitrifying bacteria are able to convert about 74% of total Kjeldahl nitrogen to nitrate. the denitrifying bacteria are able to convert this nitrate to gaseous form of nitrogen and to remove 92% of total Kjeldahl nitrogen. Different BNT process were able to reduce 24%, 64%, and 81% of organic nitrogen by ammonification, nitrification, and denitrification respectively. The COD/ N is 1 and the nitrogen removal efficiency is high. BNT is efficient in reducing TS, TSS, and TDS in the water was brought to the excellent ranges for drinking water between 50-150 mg/l. Regarding hardness, hard wastewater higher than 350 mg/l removed significantly by all BNT to bring it to soft water 180 mg/l in the end of experiment. Alkalinity was elevated by the BNT as CO3 react with H coming from nitrification to form more HCO3 ions in the water. EC values during whole experiment were changed about 10 units to return to its natural values around 160 ds.m-1 as the soluble salts cannot be removed by BNT. Turbidity of waste water was significantly removed by BNT process as microbes decompose the majority of total suspended and dissolved solid that create the turbidly.