Hallvard Ødegaard

Nitrification in a moving bed biofilm reactor

Abstract A new biofilm reactor, the moving bed reactor, was studied for nitrification purposes. The study was partly on laboratory-scale with a prepared water, and partly on pilot-scale with primary or secondary effluent as feed water. The experimental results showed that when alkalinity was in excess and there was no organic load, either the ammonium or the oxygen concentration would be limiting for the nitrification rate. The shift from the ammonium to the oxygen concentration being rate limiting occurred for an oxygen to ammonium concentration ratio of about 3 g O 2 (g NH 4 -N) −1 . The oxygen concentration had a great influence on the nitrification rate when oxygen was rate limiting. The nitrification rate was then close to a first-order function of the oxygen concentration, indicating liquid film diffusion to be the important rate limiting mechanism. Nitrification rates were reduced by increased organic loads. When the organic load exceeded 5 g total BOD 7 m 2 d −1 , the nitrification became insignificant. With a secondary effluent feed, nitrification rates of 0.7−1.0 g NO x -N (NO 3 -N + NO 2 -N) m −2 d −1 were achieved at oxygen concentrations between 4.5 and 5 g O 2 m −3 . Curves were constructed for nitrification at different organic loads when the oxygen concentration was rate limiting.

Aerobic moving bed biofilm reactor treating thermomechanical pulping whitewater under thermophilic conditions

The continuously operated laboratory scale Kaldnes moving bed biofilm reactor (MBBR) was used for thermophilic (55 degrees C) aerobic treatment of TMP whitewater. In the MBBR, the biomass is grown on carrier elements that move along with the water in the reactor. Inoculation with mesophilic activated sludge gave 60-65% SCOD removal from the first day onwards. During the 107 days of experiment, the 60-65% SCOD removals were achieved at organic loading rates of 2.5-3.5 kg SCODm(-3) d(-1), the highest loading rates applied during the run and HRT of 13-22h. Carbohydrates, which contributed to 50-60% of the influent SCOD. were removed by 90-95%, while less than 15% of the lignin-like material (30-35% of SCODin) was removed. The sludge yield was 0.23g VSSg SCOD(-1)removed. The results show that the aerobic biofilm process can be successfully operated under thermophilic conditions.

Denitrification in a packed bed biofilm reactor (biofor) : experiments with different carbon sources

The objective of this laboratory study was to investigate the efficiency of hydrolysed sludge and solid organic waste as a carbon source for denitrification in a packed bed reactor compared to ethanol and acetic acid. An artificial wastewater with a temperature in the range of 9–11°C was used. The denitrification rate, the COD consumption and utilization efficiency and the pressure drop were response parameters. Under the experimental conditions, a maximum denitrification rate of about 2.5 kg NO3-N/m3·d was achieved with ethanol, whereas acetic acid gave a lower and more variable rate below 2 kg NO3-N/m3·d. The required COD/NO3-N ratio with ethanol was close to 4.5 g COD/g NO3-N. A reduced rate was found at effluent concentrations below 15 mg COD/l. Hydrolysate from sludge and solid organic waste gave the same maximum denitrification rate as ethanol, but a ratio of 8–10 g COD/g NO3-N was required. The rate decreased at effluent concentrations below 75 mg COD/l. While close to 60% of the COD in the hydrolysate was removed, only 45% was utilized for denitrification. The removal of phosphorus was found to be three times higher than the theoretical consumption based on growth.

Phosphorus removal by granular activated alumina

Abstract Phosphorus removal from wastewater may be carried out by fixed-bed adsorption using activated alumina. In order to prevent unacceptable head-losses coarse-grained alumina must be used. Such systems have been referred to by several authors in literature. The mass transport characteristics of the system has so far, however, not been given a thorough investigation. This study uses the homogeneous surface diffusion model (HSDM) to describe the process as influenced by the system parameters. A sensitivity analysis is presented to optimize the process design for given conditions. The pH, the alumina particle size and the column length are found to be very important parameters determining the column performance. The process is very well suited for designing a beds-in-series system.

Thermal hydrolysate as a carbon source for denitrification

Thermal hydrolysate is the liquid fraction (supernatant) of thermally treated wastewater sludge. The objective of the present study was to investigate the quality of thermal hydrolysate as a carbon source for denitrification. Steady state denitrification experiments in moving bed biofilm reactors were carried out. It was demonstrated that 2/3 of the COD in the thermal hydrolysate was utilised as a carbon source in the post denitrification step, with a retention time of 52 minutes. This degree of utilisation is about the same as reported for biological hydrolysate, which generally has been considered to be of better quality as a carbon source than thermal hydrolysate. The yield of soluble COD in the thermal hydrolysis process (180°C in 30 minutes) was found to be 28%. Typical COD-yields for biological hydrolysis are around 11%.

Coagulation with Prepolymerized Metal Salts

It has been known to mankind for 4000 years that alum and iron are useful in the treatment of water. Purified alum was, however, first manufactured in the fifteenth century. In England, treatment of muddy waters by coagulation/flocculation started in the mid-seventeenth century. Today alum (or iron) coagulation represents probably the most commonly used drinking water treatment process throughout the world.

Removal of humic substances from natural waters by reverse osmosis

Abstract An investigation of the potential use of reverse osmosis for the removal of humic substances in order to remove colour and haloform precursors in small waterworks has been carried out, using three different laboratory scale reverse osmosis units and several different membranes. Membrane pore size was found to be the most important factor that influenced both the permeate quality and the product water flux. Pressure was found to have no significant influence on permeate quality, but was linearly related to product water flux. The concentration of humic substances in the influent was not found to affect product water flux but the transport of humics across the membrane was found to be dependent upon influent concentration. For the selected membranes, the removal of humic substances amounted to 80–100% in terms of colour removal, and 50–99% in terms of permanganate value reduction. The most suitable membranes for the different available units were found to be Osmonics SEPA 89 (permeate flux 251 m −2 h −1 at 15 bars), DDS 865 (permeate flux, 1201 m −2 h −1 at 40 bars) and PCI T2A (permeate flux 901 m −2 h −1 at 20 bars). At suspended solids concentrations higher than 100 mg 1 −1 of bentonite, product water flux was significantly reduced.

Fouling Control by Reduction of Submicron Particles in a BF‐MBR with an Integrated Flocculation Zone in the Membrane Reactor

Abstract Submicron particles represent one of the major foulants in the biofilm membrane reactor BF‐MBR. Reduction of the amount of submicron particles (colloids) adjacent to the membrane is one measure in order to provide better fouling control in BF‐MBR systems. A submerged hollow fiber (Zenon Zeeweed) membrane reactor was redesigned by introducing a flocculation zone below the aeration device of the membrane module. This resulted in reduction of submicron particles around the membrane from 8.2% to 6.9%, expressed in differential number percentage. The size of the most abundant particle fraction consequently increased from 0.70 to 0.84 µm. Furthermore, the modified membrane reactor design provided longer operational cycles, >40% reduction of suspended solids around the membrane, and improved retentate/concentrate characteristics, i.e., dewaterability (CST), settleability (SVI/SSV) and filterability (TTF).

Hybrid activated sludge/biofilm process for the treatment of municipal wastewater in a cold climate region: a case study

A hybrid activated sludge/biofilm process was investigated for wastewater treatment in a cold climate region. This process, which contains both suspended biomass and biofilm, usually referred as IFAS process, is created by introducing plastic elements as biofilm carrier media into a conventional activated sludge reactor. In the present study, a hybrid process, composed of an activated sludge and a moving bed biofilm reactor was used. The aim of this paper has been to investigate the performances of a hybrid process, and in particular to gain insight the nitrification process, when operated at relatively low MLSS SRT and low temperatures. The results of a pilot-scale study carried out at the Department of Hydraulic and Environmental Engineering at the Norwegian University of Science and Technology in Trondheim are presented. The experimental campaign was divided into two periods. The pilot plant was first operated with a constant HRT of 4.5 hours, while in the second period the influent flow was increased so that HRT was 3.5 hours. The average temperature was near 11.5°C in the overall experimental campaign. The average mixed liquor SRT was 5.7 days. Batch tests on both carriers and suspended biomass were performed in order to evaluate the nitrification rate of the two different biomasses. The results demonstrated that this kind of reactor can efficiently be used for the upgrading of conventional activated sludge plant for achieving year-round nitrification, also in presence of low temperatures, and without the need of additional volumes.

Chemical Wastewater Treatment — Value for Money

The British often use the expression “value for money”. In this paper we will try to demonstrate that this expression is very valid for chemical wastewater treatment. Different aspects of wastewater treatment will be examined, such as: Treatment efficiency Area requirement Sludge production Cost Ecological impact.