Nitrogen removal from hydroponic culture wastewater by autotrophic denitrification using thiosulfate

Abstract

Using the upflow biological filter reactor, sulfur denitrification using thiosulfate of hydroponic culture wastewater was examined. Start-up periods of the reactor were one to two weeks. About 90% of nitrogen removal ratio were achieved over 80 days, at 6.3 kg/m3·days of nitrogen loading. Shock loading among 0.56-2.8 kgN/m3· day did not affect the reactor performance. However, when temperature went below 15°C, the effluent characteristics became poor. Suitable S/N and IC/N ratios were calculated as 3.3 and 0.15, respectively. The activities of sulfur denitrification, heterotrophic denitrification and sulfur reduction were examined by the bath experiments under several conditions using biomass grown in the reactor. In the anoxic conditions, denitrification using thiosulfate was occurred stoichiometrically in the presence of thiosulfate. The denitrification activity was highest (17 mgN/gBiomass·hr). When the electron donor was not added to the substrate, denitrification occurred using sulfur granules accumulated in the biomass. Seventy mg of sulfur granule were accumulated in one g of biomass. The denitrification activity using sulfur granules was 2.9-5.0 mgN/gBiomass·hr. Heterotrophic denitrification occurred in the presence of organic matter. The activities were 1.4-5.4 mgN/gBiomass·hr. In the anaerobic conditions, the accumulated sulfur was reduced to sulfide at a rate of 1.4 mgS/gBiomass·hr. These results suggested that sulfur denitrification, heterotrophic denitrification and sulfur reduction bacteria coexisted in the biofilm and sulfur cycle was established in the reactor. Accumulated sulfur plays an important role in the sulfur denitrification.

Enhancement of nitrate removal in constructed wetlands utilizing a combined autotrophic and heterotrophic denitrification technology for treating hydroponic wastewater containing high nitrate and low organic carbon concentrations

“…Yamamoto-Ikemoto et al (2000) also observed that specific sulfur denitrification activities using thiosulfate were 2-5 times greater than that using elemental sulfur. However, elemental sulfur was mainly used for autotrophic denitrification because of its cost effectiveness, high sulfur content to mass ratio among the reduced sulfur compounds, and ease of handling (Hashimoto et al, 1987;Batchelor and Lawrence, 1978).…”

Beneficial co-treatment of simple wet flue gas desulphurization wastes with freshwater sewage through development of mixed denitrification–SANI process

“…Mixed sulphide and thiosulphate provide an opportunity to expedite nitrogen removal in the subsequent anoxic reactor. Not only does thiosulphate act as an electron donor for autotrophic denitrification (AD) as does sulphide [12,13], but it also induces faster AD than that on sulphide [14]. Compared with sulphate reduction, sulphite reduction demands less organics, thus making a small portion of organics remained possibly after biological sulphur reduction (BSR).…”

Autotrophic Biological Denitrification for Complete Removal of Nitrogen from Septic System Wastewater

“…Advantages of autotrophic sulfur oxidizing denitrification for wastewater treatment include: (1) high nitrate removal efficiencies, (2) elemental sulfur, which is a by-product of oil processing, is less expensive than ethanol or methanol, (3) little or no external carbon source is required, minimizing the possibility of carry-over of excess organic carbon into the effluent, (4) sulfur oxidizing denitrification can take place under aerobic conditions (Yamamoto-Ikemoto et al, 2000). Although more biomass is produced, this eliminates the need to deoxygenate the influent wastewater, (5) due to lower biomass yields for autotrophic bacteria, less sludge is produced and (6) autotrophic sulfur oxidizing denitrifying bacteria produce less N 2 O (a greenhouse gas) than heterotrophic denitrifying bacteria (Park et al, 2002).…”