Existing municipal effluent treatment plants designed earlier for the BOD removal are usually not suitable for nitrification at low temperatures, because of :
Small plant dimensions and low sludge age, respectively
Consequences are that in the cases of nitrification expensive plant extensions are required.
2. Our problem solution results in
Plants being upgraded into fluidised bed reactors using microorganisms immobilised on adsorbing LEVAPOR-carrier.
Nitrifying bacteria immobilised on adsorbant carriers become more robust and efficient, produce lower quantities of excess sludge and are able to maintain their activity even after a storage over 12 months.
A. Upgrading of a small municipal WWTP with aerated basin of 45 m³, for nitrification in winter, by filling it with 12 vol.% of LEVAPOR carrier
As a possible alternative to plant extension, it was considered to establish the nitrification by a susequent WWTP- upgrading via immobilisation of nitrifying sludge on 12 vol.% of adsorbing LEVAPOR-carrier.
After addition into the basin the carrier cubes became colonised and fluidised directly and despite the low temperatures (November) the nitrification was established at 17°C within two to three weeks and kept efficient achieving 70 to 80% nitrification over several months, despite even the lower temperatures in December (12 °C).
Nitrification performance of the plant at different temperatures
Immobilising the activated sludge, nitrification was established within 2 to 3 weeks.
The nitrification remained stable and efficient, even at lower temperatures, of 8 to 13°C with increased volumetric N-loading rates.
The existing aeration system was proven as sufficient for almost a complete fluidisation of the colonised carrier cubes.
Removal of excess biomass from the surface of the carrier cubes occurred automatically by fluidisation without any additional measure.
B. Nitrification and removal of hazardous pollutants from municipal effluents ( pilot plant trials)
Comparison of immobilised -LEVAPOR-carrier - vs. suspended sludge
In two parallel operated fluidised bed reactors, each of 3,1 m³, nitrification and hazardous pollutant removal of immobilised and suspended biomass have been compared. In addition to higher degree of nitrification and denitrification ( due to inner pores of carrier cubes ), immobilised biomass achieved also a remarkably higher removal of polycondensed aromatic compounds.
N2O-production was investigated during nitrogen removal using aerobic granular sludge (AGS) technology. A pilot sequencing batch reactor (SBR) with AGS achieved an effluent in accordance with national discharge limits, although presented a nitrite accumulation rate of 95.79% with no simultaneous nitrification–denitrification. N2O production was 2.06 mg L−1 during the anoxic phase, with N2O emission during air pulses and the aeration phase of 1.6% of the nitrogen loading rate. Batch tests with AGS from the pilot...
Nitrifying granules have a high sedimentation property and an ability to maintain a large amount of nitrifying bacteria in a reaction tank. Our group has examined the formation process of nitrifying granules and achieved high-rate nitrification for an inorganic synthetic wastewater using these granules. In this research, a pilot-scale test plant with an 850-liter reaction tank was assembled in a semiconductor manufacturing factory in order to conduct a continuous water conduction test using real electronics...
The effect of inorganic suspended solids (ISS) on nitrification in freshwater samples has been described inconsistently and remains unclear. This study therefore investigated the effects of the chemical characteristics and concentration of ISS on the nitrification rate by focusing on Nitrosomonas europaea and Nitrobacter winogradskyi as the two most dominant nitrification species in freshwater. Batch-wise experiments were conducted using three chemically well-characterized ISS (i.e. the clay minerals montmorillonit...
Nitrifiers are the slowest growing bacteria used in conventional biological wastewater treatment. Furthermore, their growth rate is seriously hampered by low temperature. As a result, the volume needed for nitrification dominates the volume of the biological reactors at a wastewater treatment plant. As a way of enhancing nitrification and reducing this volume, bioaugmentation can be used. Nitrifiers from a side-stream plant can be inoculated to the mainstream process, which is thereby boosted. The effect of...
Raw water resources in Kafr El-Sheikh Governorate are affected by many contaminants particularly during the winter season and low demand period of the Nile River, in which water level decreases and organic matter increases resulting in decreased dissolved oxygen, and increased ammonia, nitrite and bacterial load in the water. In this study, physicochemical and microbiological characteristics of water samples taken seasonally from selected sampling sites on seven main canals in Kafr El-Sheikh Governorate were...