Effects of Environmental Parameters on Nitrification and Denitrification in Duckweed Based and Algae Based Stabilization Containers

Abstract

ln outdoor batch experiments , algae-based and duckweed (Lemna gibba)-based wastewater containers have been monitored over a period of 15 days in eight experiments with to variable environmental factors (00 and pH) . Experiments (1 to 4) were with zero 00, pH ranges (8-9, 7-8, 6-7 and 5-6) and initial total nitrogen concentration of approximately 100 mg-N/I respec tively . Whereas experiments (5 to 8) were conducted at approximately the same initial total nitrogen concentration and pH ranges , but at saturated 00. At pH range between (5-7), algae -based and duckweed -based containers removed between (21 %-31 %) and between (28 %- 40 %) of the initial total nitrogen concentration respectively, while the overall removals at pH rang e (7-9) were between (76 %- 86 %) in ABC and (72% -74%) in DBC. The nitrogen removal rate in ABC and DBC at pH range (5-7) was 0.4 and 0.5 g-N m-2 d-1 respectively, while at pH range (7 -9 ) wa s 1.2 in ABC and 1. 1 g-N m-2 d-1 in OBC. At pH range between (5 -7) , the nitrogen losses resulted from the combined effect of ammonia volatilization and denitrification in ABC and DBC were 8% and 5% of the initial total nitrogen concentration s respectively , while at pH range between (7-9) it was 58% in ABC and 40% in OBC. The nitrogen losses via ammonia volatilization in ABC and DBC at pH range between (5-7) were 6% and 3% of the initial total nitrogen concentrations respectively, while at pH range (7-9) it was 55 °/o in ABC and 37% in OBC. The loss due to denitrification in ABC and OBC at zero 00 was between (3%-6%) and (3%-4%) of the initial total nitrogen concentrations respectively , while at saturated 00 the losses were approximately 0.5% in both container systems. The nitrogen removal via sedimentation in ABC and DBC at zero DO and pH ranges (5 -9) was between (16%-21 %) and between (11%-21%) of initial total nitrogen concentration respectively, whereas at saturated 00 and the same pH ranges it was between (17%-27%) in ABC and between (10% -23%) in DBC respectively . At high pH range between (8-9), it was observed that part of the sediments consisted of settled died duckweed. Therefore, nitrogen content in the sediments of ABC was nearly equal to that in ABC, but, in general the nitrogen in ABC was higher than that in DBC.