Treatment of municipal wastewater in a CIRCOX® airlift reactor with integrated denitrification

1997 ◽  
Vol 36 (1) ◽  
pp. 173-181 ◽  
Author(s):  
C. T. M. J. Frijters ◽  
D. H. Eikelboom ◽  
A. Mulder ◽  
R. Mulder
Keyword(s):  
Activated Sludge ◽  
Municipal Wastewater ◽  
Loading Rate ◽  
Airlift Reactor ◽  
Loading Rates ◽  
Activated Sludge System ◽  
Conversion Rates ◽  
Substrate Conversion ◽  
Airlift Pump ◽  
Interesting Alternative

In this study it was investigated whether the CIRCOX® airlift technology with integrated denitrification was suitable to treat municipal wastewater. The standard CIRCOX® reactor was extended with an anoxic compartment. The sludge on carrier is circulated alternately over the anoxic and oxic compartments by means of an airlift pump. The study was performed in two pilot reactors, a standard CIRCOX® reactor and a CIRCOX® reactor with integrated denitrification. Concerning BOD conversion and nitrification, no differences between the two systems were observed. It was shown that both BOD and nitrogen were removed efficiently. In the effluent, mean soluble BOD concentrations of 7 mg/l were attained at varying COD loading rates. Nitrification was complete in both reactors at temperatures above 15°C and at COD conversion rates of more than 2.5 kg COD/m3/d. Nitrification rates below 15°C were higher as compared to a low loaded activated sludge system. Substrate conversion rates were found to be constant throughout the denitrifying reactor. Denitrification matched the rates theoretically feasible. This could be achieved by controlling the recirculation and the aeration in relation to the loading rate. It can be concluded that the denitrifying CIRCOX® airlift technology seems to be an interesting alternative to treat municipal wastewater.

Municipal wastewater treatment in Berlin with deep tanks and flotation for secondary clarification

1996 ◽  
Vol 33 (12) ◽  
pp. 199-210
Author(s):  
R. Gnirss ◽  
A. Peter-Fröhlich ◽  
V. Schmidt
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Energy Requirements ◽  
Municipal Wastewater Treatment ◽  
Space Saving ◽  
Process Energy ◽  
Near Future ◽  
Interesting Alternative ◽  
Pilot Tests

For municipal wastewater treatment, space-saving 10m deep activated sludge tanks are an interesting alternative to conventional tanks of shallow construction. Results from pilot tests in the Berlin-Ruhleben WWTP have shown that the biological P-elimination, nutrification and denitrification processes can be implemented as in shallow tanks. However, the activated sludge did not settle satisfactorily. Flotation was implemented in the process for secondary clarification and in the meanwhile has shown to be advantageous. Tests run over a period of some years with the pilot plant have proven the feasibility of this process. Energy requirements for both systems were found to be approximately the same. A cost estimate based on a preplan revealed a 10% advantage in favour of the 10m WWTP with flotation. For these reasons, one 10m WWTP with flotation for secondary clarification and a capacity of 80,000 m3/d will be built in Berlin in the near future.

Performance evaluation of a UASB - activated sludge system treating municipal wastewater

2001 ◽  
Vol 43 (11) ◽  
pp. 323-328 ◽  
Author(s):  
M. von Sperling ◽  
V. H. Freire ◽  
C. A. de Lemos Chernicharo
Keyword(s):  
Activated Sludge ◽  
Municipal Wastewater ◽  
Large City ◽  
Pilot Scale ◽  
Uasb Reactor ◽  
Warm Climate ◽  
Conventional Activated Sludge ◽  
Activated Sludge System ◽  
Solids Concentration ◽  
Sufficient Detail

Recent research has indicated the advantages of combining anaerobic and aerobic processes for the treatment of municipal wastewater, especially for warm-climate countries. Although this configuration is seen as an economical alternative, is has not been investigated in sufficient detail on a worldwide basis. This work presents the results of the monitoring of a pilot-scale plant comprising of an UASB reactor followed by an activated sludge system, treating actual municipal wastewater from a large city in Brazil. The plant was intensively monitored and operated for 261 days, divided into five different phases, working with constant and variable inflows. The plant showed good COD removal, with efficiencies ranging from 69% to 84% for the UASB reactor, from 43% to 56% for the activated sludge system only and from 85% to 93% for the overall system. The final effluent suspended solids concentration was very low, with averages ranging from 13 to 18 mg/l in the typical phases of the research. Based on the very good overall performance of the system, it is believed that it is a better alternative for warm-climate countries than the conventional activated sludge system, especially considering the total low hydraulic detention time (4.0 h UASB; 2.8 h aerobic reactor; 1.1 h final clarifier), the savings in energy consumption, the absence of primary sludge and the possibility of thickening and digesting the aerobic excess sludge in the UASB reactor itself.

Oligonucleotide probe hybridization and modeling results suggest that populations consuming readily degradable substrate have high cellular RNA levels

2002 ◽  
Vol 45 (6) ◽  
pp. 115-126 ◽  
Author(s):  
D. Frigon ◽  
D.B. Oerther ◽  
E. Morgenroth ◽  
L. Raskin
Keyword(s):  
Activated Sludge ◽  
Municipal Wastewater ◽  
Loading Rate ◽  
Wastewater Treatment Plants ◽  
Oligonucleotide Probe ◽  
Municipal Wastewater Treatment ◽  
Bacterial Populations ◽  
Model Simulations ◽  
Low Level ◽  
High Level

Analyses based on ribosomal RNA (rRNA)-targeted hybridization performed in our laboratory identified two types of bacterial populations: a population with a high RNA level per biomass and a population with a low level of RNA per biomass. To extend these descriptions, the diurnal dynamics of the RNA pool were monitored by rRNA-targeted oligonucleotide probe membrane hybridization. Under the typical diurnal variation in COD loading rate experienced by municipal wastewater treatment plants, the RNA level of the bacterial population with a high level of RNA per biomass varied with changes in the COD loading rate. Under the same conditions, the RNA level of the population with low RNA level per biomass remained constant. A structured biomass model was developed to describe these data. Substrate COD was divided into a readily biodegradable and a slowly biodegradable COD fraction. It was assumed that two specialized populations coexist in municipal activated sludge treatment systems. One population consumes readily degradable COD and the other consumes slowly degradable COD. According to model simulations, the population consuming readily degradable COD has a high level of RNA per biomass under variable substrate concentrations. Comparatively, the population consuming slowly degradable COD has a low level of RNA level per biomass. Furthermore, model simulations reproduced the two diurnal RNA profiles observed in a full-scale municipal activated sludge system. Therefore, we suggest that two populations can be distinguished in municipal activated sludge systems: a population consuming readily degradable substrate and a population consuming slowly degradable substrate.

Influence of temperature and sludge loading on activated sludge settling, especially on Microthrix parvicella

1998 ◽  
Vol 37 (4-5) ◽  
pp. 27-35 ◽  
Author(s):  
S. Knoop ◽  
S. Kunst
Keyword(s):  
Wastewater Treatment ◽  
Low Temperature ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Loading Rate ◽  
Wastewater Treatment Plants ◽  
Full Scale ◽  
Causative Organism ◽  
Foam Formation ◽  
Microthrix Parvicella

During recent years modern full scale wastewater treatment plants with biological nitrification, denitrification and phosphorus removal have had increasing problems with foam formation on the surfaces of aerobic tanks and with bulking activated sludge. The results of a survey in 1995 (Kunst and Knoop, 1996) showed that most often the filamentous bacterium Microthrix parvicella is responsible for these problems. Up to today there is only little knowledge about its selection criteria in activated sludge. Therefore several experiments were done in full scale activated sludge plants and in laboratory systems under defined conditions to investigate the influence of low (< 0.1 kg/(kg·d)) and high (≤ 0.2 kg/(kg·d)) BOD5-sludge loading rates on the growth and morphology of M. parvicella and the settlement of activated sludge. Furthermore the influence of temperatures of 5°C, 12°C and 20°C on the growth of M. parvicella was investigated. It was shown that M. parvicella grows at low BOD5-sludge loading rate and low temperature and is the main causative organism of bulking and foaming sludge in nutrient removal plants. On the basis of this investigation it was concluded that the growth of M. parvicella and the settling problems of the activated sludge resulting from excessive growth of this filament will always appear in modern municipal wastewater treatment plants with BOD5-sludge loading rate ≤ 0.1 kg/(kg·d) especially under low temperature conditions.

Modeling of biofouling by extracellular polymers in a membrane separation activated sludge system

1998 ◽  
Vol 38 (4-5) ◽  
pp. 497-504 ◽  
Author(s):  
H. Nagaoka ◽  
S. Yamanishi ◽  
A. Miya
Keyword(s):  
Activated Sludge ◽  
Loading Rate ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Organic Loading Rate ◽  
Sudden Increase ◽  
Organic Loading ◽  
Reactor Performance ◽  
Filtration Resistance ◽  
Activated Sludge System

A Laboratory-scale experiment was conducted to investigate the mechanism of the bio-fouling in the submerged membrane separation activated sludge system. Flat-sheet-type membrane module was used and the change of the pressure and the filtration resistance was measured. Two reactors were operated in parallel to investigate the influence of organic loading rate on the reactor performance. A mathematical model was developed to simulate temporal changes of suction pressure, flux and filtration resistance considering accumulation, detachment and consolidation of EPS on the membrane surface. Parameters in the model were determined so that the calculated results fit to the measured variation curves. The high load reactor (1.5g-TOC L−1 day−1) showed a sudden increase of the pressure and a decrease of flux after 40th days, which could not be recovered even by membrane cleanings, while the low load reactor (0.5g-TOC L−1 day−1) showed little increase of the pressure until 120th days. The measured pattern of the flux, the pressure and the resistance were well explained by the developed model. Using the model, influence of operational parameters, such as organic loading rate, flux and shear stress working on the membrane, on the reactor performance was evaluated. It was concluded that the flux is the most influential parameter and when the flux is more than a critical value, which is as low as 0.1 m day−1, maximum time during which the set flux can be maintained becomes very short.

Achieving nitrification in pure oxygen activated sludge by seeding

1998 ◽  
Vol 37 (4-5) ◽  
pp. 573-577 ◽  
Author(s):  
J. B. Neethling ◽  
Carlo Spani ◽  
Joe Danzer ◽  
Bruce Willey
Keyword(s):  
Activated Sludge ◽  
Full Scale ◽  
Pure Oxygen ◽  
Waste Activated Sludge ◽  
Seeding Rate ◽  
Loading Rates ◽  
Solids Loading ◽  
Activated Sludge System ◽  
Oxygen System ◽  
Full Scale Tests

An innovative “seeding” approach was used to increase the nitrification capacity of a pure oxygen activated sludge plant. In this approach, waste activated sludge from a parallel air activated sludge system was used to seed nitrifiers to the pure oxygen plant to increase the apparent sludge age and achieve nitrification under the high loading in the pure oxygen system. Calculations indicate that nitrification can be achieved at a traditional sludge age of 3 days with a seeding rate of 20 percent. Full-scale tests showed that nitrification can be achieved at a seed rate of 35 percent and a traditional sludge age of 4.6 days, producing effluent ammonia below 5 mg/l. Secondary clarification remained good during the operation of the system even at the higher solids loading rates, with effluent TSS concentrations at 6 mg/l.

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