Effect of the Sewage and Wastewater Plant Effluent on the Algal Growth Potential in the Nakdong River Basin

Abstract

Effect of the effluent of the sewage and wastewater plants on the algal growth was investigated from the 19 plants located in the Nakdong river basin. Most of the samples showed high values of the algal growth potential (AGP) when they were mixed with natural river water at 20% of final concentration. At 20% of the mixing ratio, the mixed effluents of sewage and wastewater showed 3.5 and 1.8 times higher AGP than those of the natural river water. The higher AGP values are attributable to the high contents of phosphorus and ammonium in the effluent. The mixing ratio of effluents of the discharge/river flow was highest in the Kumho River (42.8%) followed by the middle of Nakdong River (22.7%), Kam Stream (13.9%), Byungsung Stream (13.3%), Yangsan Stream (7.9%), and Young River (5.4%). Comparison of the trophic state of the effluents with natural river water indicated that the effluents showed higher trophic values than natural water. Concentrations of total phosphorus, total nitrogen and conductivity in the effluents were 12.3, 4.9 and 5.3 times higher than the those found in natural river water respectively. The AGP values were highly related with the trophicity of the water especially on the concentrations of phosphate and ammonium. Toxicities of the treated sewage water, wastewater and livestock waste water tested by the luminescent bacteria, Vibrio fischerii were generally low.

Algal Growth Potential of Microcystis aeruginosa from Reclaimed Water

“…Irrespective of the treatment processes, the AGP values decreased as the volume of dilution increased. These results were consistent with previous studies that explained a correlation between the increase in dilution ratio and the decrease in AGP values (Seo et al, 2003;Shin et al, 2000). Although the growth rate and biomass accumulation of M. aeruginosa are considered to be complex functions related to nutrient availability and settings of aquatic ecosystems (e.g., water temperature, sunlight, water velocity, turbidity, salinity, etc.…”

“…Although there are multiple limiting nutrients (e.g., nitrogen, phosphorus, iron, etc.) in natural aquatic systems (Biggs, 2000;Donald et al, 2013;Parrish, 2014;Xu et al, 2010), SRP-limited growth of M. aeruginosa using reclaimed water from various WRRFs was proposed (Paerl et al, 2011;Seo et al, 2003). Thus, the SRPlimited growth of M. aeruginosa was evaluated in this study using the Monod's equation (Monod, 1949), as shown in eq 2,…”

“…In the Republic of Korea, AGP tests have been extensively used to determine the maximum density of algae and to assess the degree of eutrophication of rivers and lakes (Shin and Cho, 2000). Additionally, AGP tests have been applied to assess the effect of effluents from water resource recovery facilities (WRRFs) on the eutrophication of rivers and lakes (Seo et al, 2003). Based on previous studies (Seo et al, 2003;Shin and Cho, 2000), most effluents from WRRFs have been found to have greater AGP values than high productivity (i.e., 20 mg L À1 of algal dry weight, 20 mgdw L À1 ).…”

“…Additionally, AGP tests have been applied to assess the effect of effluents from water resource recovery facilities (WRRFs) on the eutrophication of rivers and lakes (Seo et al, 2003). Based on previous studies (Seo et al, 2003;Shin and Cho, 2000), most effluents from WRRFs have been found to have greater AGP values than high productivity (i.e., 20 mg L À1 of algal dry weight, 20 mgdw L À1 ). Thus, the augmentation of wastewater effluents can cause both eutrophic (10 mgdw L À1 ) and hypertrophic (20 mgdw L À1 ) conditions for rivers and lakes.…”