Simultaneous nutrient and organic matter removal from wastewater by aerobic granular sludge process

V. Denisova*, K. Kokina, K. Gruskevica and L. Mezule

Riga Technical University, Faculty of Civil Engineering, Water Research and Environmental Biotechnology Laboratory, Kipsalas 6a, LV-1048, Riga, Latvia
*Correspondence: viktorija.denisova@rtu.lv

Abstract:

Aerobic granular sludge (AGS) technology offers several benefits, such as simultaneous removal of nutrients and organic matter from wastewater, stronger granule structure, excellent settleability, and high resistance to toxicity. However, the formation of granules can take a long time and needs to be dense and stable.

In this study, the formation of aerobic granules in sequencing batch reactors (SBRs) using a granular activated carbon (GAC) and aluminium sulphate coagulant were evaluated for the simultaneous removal of nutrient (phosphorus (TP) and nitrogen (TN)) and organic matter (chemical oxygen demand (COD)) from wastewater. The reactors were continuously operated for 107 days and were fed with synthetic media and real domestic sewage. However, adaptation process with the synthetic wastewater led to relatively slow granulation process (sedimentation rate of sludge flocks was 3 m h^-1). During the experiments, there was no visible formation of granules in SBRs based on the analysis of the sludge samples, only the formation of aggregate structures similar to flocks. However, the results showed that total phosphorus (TP) removal efficiency was over 90% in SBR operated with aluminium sulphate. However, COD and total nitrogen (TN) removals were higher in GAC SBR, 75% and 10%, respectively. Thus, even if granules are not developed yet, the system is working efficiently. The results of this study could be useful in the development of AGS technology for full-scale wastewater treatment plant.

Key words:

Effect of potassium application rate and timing on alfalfa yield and potassium concentration and removal in Tennessee

M. Pourebrahimi Foumani¹, H. Savoy², N. Atotey³ and X. Yin¹*

¹University of Tennessee, Department of Plant Sciences, West Tennessee Research and Education Centre, 605 Airways Blvd., Jackson, TN 38301-320, USA
²University of Tennessee, Department of Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, USA
³University of Tennessee, Department of Biosystems Engineering and Soil Science, West Tennessee Research and Education Centre, 605 Airways Blvd., Jackson, TN 38301-320, USA
*Correspondence: xyin2@utk.edu

Abstract:

Alfalfa (Medicago sativa L.) is the most important forage crop in the world and potassium plays a significant role in achieving high yields. A field experiment was conducted during the 2012–2014 growing seasons at the University of Tennessee in Springfield. The experimental design was a split-split plot that included four levels of potassium (K) application rates (0, 67.25, 134.50, and 269.00 kg K₂O ha^-1) as the main plots and two K application times (green-up and split) as the subplots, and harvest dates as sub-subplots. The results demonstrated that the dry matter yield (DM) increased significantly with each increment in K application rate up to 134.50 kg K₂O ha^-1; however, the highest K fertilizer application (269 kg K₂O ha^-1) did not result in a significant yield increase relative to 134.50 kg K₂O ha^-1, because some luxury consumption of K occurred at the highest rate due to yield leveling off while K₂O uptake continued to rise. Potassium concentration and K removal increased with K fertilizer at rates beyond those that maximized yield, indicating luxury consumption of K. The greatest K concentration and removal were recorded at 269 kg K₂O ha^-1 in all harvest months. The split application was more beneficial than applying full K at the time of green-up due to higher dry matter, K concentration, and K removal in alfalfa. In conclusion, 134.50 kg K₂O ha^-1 is adequate for maximizing alfalfa yield; split application of K is sometimes superior to the single dose of K fertilizer in alfalfa production.

Key words:

concentration, dry matter yield, fertilizer, Medicago sativa, nutrient removal