Tag Archives: organic matter

1082-1092 V. Denisova, K. Kokina, K. Gruskevica and L. Mezule
Simultaneous nutrient and organic matter removal from wastewater by aerobic granular sludge process
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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.

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99–110 L. Szajdak, P. Kuldkepp, E. Leedu, T. Teesalu, A. Toomsoo and R. Kõlli2
Some biochemical aspects of Fragi-Stagnic Albeluvisols’ organic matter
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Some biochemical aspects of Fragi-Stagnic Albeluvisols’ organic matter

L. Szajdak¹, P. Kuldkepp², E. Leedu², T. Teesalu², A. Toomsoo² and R. Kõlli2*

¹Research Centre for Agricultural and Forest Environment, Polish Academy of Sciences, ul. Bukowska 19, 60-809 Poznań, Poland; e-mail: szajlech@man.poznan.pl
²Institute of Agricultural and Environmental Sciences, Estonian Agricultural University, Kreutzwaldi 64, 54014 Tartu, Estonia; e-mail: raimo@eau.ee
*Author for correspondence

Abstract:

The concentrations of N-NH4+, N-NO3–, Ntotal, total (TOC) and water extractable (DOC) organic carbon, P, K, Ca, Mg, S, the activity of nitrate reductase, the activity of urease activity as well as indole-3-acetic acid (IAA) were investigated in Fragi-Stagnic Albeluvisols’ organic matter under different organic and mineral fertiliser regimes from a long-term soil formation of a field experiment with three-field crop rotation (potato – spring wheat – spring barley) at Eerika near Tartu, Estonia, and also in the forest of Tiksoja. The concentrations of Ntotal, IAA, the activity of urease and also C/N ratios were generally highest in the forest soil of Tiksoja.
Consequently, characteristics, distributions and conversions in organic matter were found in the proportions of chemical and biochemical factors, particularly after mineral and organic fertilisers. The following kinds of fertilisers increased the activity of urease in the order: WOM/N-120 < FYM/N-120 < RS/N-120 (accordingly, WOM – without organic manure, FYM – farmyard manure, RS – recultivation substance), and increased the activity of nitrate reductase: WOM/N-120 > RS/N-120 > FYM/N-120. The highest increase of IAA was determined in the soil fertilised with RS/N-120.
The experiment was characterised by the highest activity of urease, and the highest increase of IAA and also TOC in soils fertilised with RS/N-120. The various fertiliser regimes were different both for their biochemical factors as well as the crop yields. WOM/N-120 as a mineral fertiliser and RS/N-120 as an organic one revealed the highest crop yield of potato, spring wheat, and spring barley.

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63–67 E. Lauringson and L. Talgre
Problems of abandoned fields
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Problems of abandoned fields

E. Lauringson and L. Talgre

Department of Field Crop Husbandry, Estonian Agricultural University, Kreutzwaldi 64, 510014 Tartu, Estonia; e-mail: ennlaur@eau.ee

Abstract:

The study was based on data gathered in 1995–2002 in areas where plant cultivation was discontinued for various reasons and at various times. The objective of the study was to track changes in plant community, biomass production and soil weed seedbank in the abandoned fields.
The discontinuation of cultivation resulted in the emergence of plant communities, which were characterized for the first 1–2 years by a considerable proportion of annual species. The length of the period with annual species having a large representation in a community depended in many cases on the spread of Elytrigia repens in the abandoned fields. In land left idle for 5–6 years, perennial species supplanted annual species. Apart from E. repens, aggressive species turned out to be Cirsium arvense and Artemisia vulgaris (predominantly scattered all over the field). Weed seed density in the ploughed layer (30 cm) of abandoned fields amounted 157,000 to 666,000 seeds m-2, with the upper 10-cm layer accommodating up to 51% of the total seedbank. The biomass produced by plants depended on the texture of the soil and the age of the plant community, being 32.6 t ha-1 at the maximum. The accumulation of organic matter on and in the soil is a positive development in abandoned fields. Abundant residue contributes to an improvement of the physical and mechanical properties of the topsoil layer, reducing soil bulk density and decelerating soil compaction. The surface residue is a favorable environment for soil fauna.

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