Pilot-scale Biological Nutrient Removal Research Articles

Preliminary Investigation of an Installed Pilot-Scale Biological Nutrient Removal Technology (BNRT) for Sewage Treatment

Water utilities, commercial and industrial establishments are required to upgrade or install new treatment systems to comply with the revised effluent standards issued by the Department of Environment and Natural Resources – Environment Management Bureau (DENR – EMB) which now includes removal and monitoring of nutrients (nitrogen and phosphorus components). One solution is to utilize a biological nutrient removal technology (BNRT) system capable of removing nutrients from sewage. The on-going study aims to investigate the performance of the pilot-scale system in the removal of nutrients from sewage. The designed pilot-scale anaerobic-anoxic-oxic (A2O) process with a total hydraulic retention time of 8.37 hrs. was operated in an existing sewage treatment plant (STP). System modification was adapted to ensure continuous operation. Dissolved oxygen (DO) and temperature of each compartment were evaluated after 45 days of system modification. The DO of the anaerobic and oxic compartment remained within the required range, while the internal recycling flowrate and/or aeration must be adjusted to achieve a DO concentration of 0.20 – 0.50 mg/L in the anoxic compartment. The research is financially supported by the Philippine Council for Industry, Energy and Emerging Technology Research and Development of the Department of Science and Technology (PCIEERD Project No. 04176).

Redworm elimination in an integrated fixed-film activated sludge reactor

Two pilot-scale biological nutrient removal bioreactors were operated side by side under selected flow rate conditions. One reactor was operated under an integrated fixed-film activated sludge (IFAS) reactor configuration, and the second reactor was operated under a conventional activated sludge reactor configuration. The relatively high dissolved oxygen (DO) and low food-to-microorganism ratio created a favourable environment for the proliferation of redworm identified as Aeolosoma hemprichi in the IFAS reactor from day 116, which led to significant deterioration on ammonia removal in the IFAS reactor. The removal efficiencies of chemical oxygen demand (COD) and phosphorus were not significantly affected by the redworm bloom. Several strategies were applied to eliminate the redworms from the IFAS reactor. The most effective strategy was shutting off the DO supply in the aerobic zone and stopping the influent feed for 48 h. Finally, it took about 1·5 months for the IFAS reactor to recover from performing the worm elimination strategy.

Modeling the biotransformation of trimethoprim in biological nutrient removal system.

A pilot scale biological nutrient removal (BNR) process, batch experiments and modeling exercises were employed to investigate the removal and biotransformation of trimethoprim (TMP) in a BNR activated sludge process. The concentrations of the active microbial groups - ammonia oxidizing bacteria (AOB), ordinary heterotrophic organisms (OHOs) and polyphosphate accumulating organisms (PAOs) - in the BNR bioreactor were quantified through modeling of the pilot bioreactor. The overall TMP removal efficiency for the pilot BNR process was 64 ± 14% while the TMP biotransformation efficiencies in the anaerobic, anoxic and aerobic zones were 22 ± 20%, 27 ± 8% and 36 ± 5% respectively. Batch tests with and without nitrification inhibition showed that AOB played a role in the biotransformation of TMP in BNR activated sludge. A pseudo first order model which incorporated the contributions of PAOs, OHOs and AOB to the overall biodegradation of TMP was found to describe the biodegradation of TMP in batch tests with and without nitrification inhibition. This model showed that PAOs, OHOs and AOB contributed towards the biotransformation of TMP in aerobic BNR activated sludge with the biotransformation rate constants following the trend of kAOB > kOHOs > kPAOs.

Effect of Flow Rate Increase on the Performance of a Pilot-Scale Biological Nutrient Removal Reactor

AbstractNutrient removal in two identical pilot-scale reactors is assessed at influent flow rates of 30, 45, and 60 L/min. The bacteria community structure of nitrifiers and denitrifiers and the p...

Effects of temperature on nutrient removal performance of a pilot-scale ABR/MBR combined process for raw wastewater treatment

For the purpose of achieving relatively high efficiency, low energy demands, and easy maintenance for nutrient removal, the performance of a pilot-scale biological nutrient removal process consisting of anaerobic baffled reactor and membrane bioreactor has been evaluated for 301 d in treating two kinds of raw wastewaters. The results showed that the process enabled a relatively stable and high performance in both organics and nutrient removals, and high quality effluent was achieved under temperature of 25 ± 5°C. When the ambient temperature were 10 ± 5 and 35 ± 5°C, average COD, NH4+-N, TN, and TP removal efficiencies of both kinds wastewaters were more than 88, 87, 70, and 75%, respectively. Analysis of the results by fluorescence in situ hybridization showed that ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and phosphorus-accumulating organisms were always the enriched micro-organisms in the process during the change of temperature, ensuring the efficient nutrient removal under ambient environment with low energy exhaustion.

Determination of kinetic parameters in a pilot scale BNR system treating municipal wastewater

Kinetics for the biological processes of nitrification, denitrification and carbon oxidation were
 studied in the aerobic and anoxic phases of a pilot scale Biological Nutrient Removal (BNR)
 plant treating municipal wastewater. The configuration of the treating system is based on the
 combination of the UCT (University of Cape Town) design and the step feeding process in a
 cascade denitrification.
 In order to study the process kinetics and to obtain reliable values for the investigated kinetic
 parameters batch experiments were performed. For this purpose, continuous feeding of the
 treating system was interrupted for a given period of time and the pilot plant was turned into a
 batch mode of operation. Thereafter, addition of NO3
 --N and NH4
 +-N into the anoxic and
 aerobic compartments of the treating plant, respectively, followed, whereas adequate initial
 concentration of a carbon source (municipal wastewater or synthetic substrate) was ensured
 in the mixed liquor. Experimental data indicated that the examined biological processes
 followed saturation kinetics.
 The maximum specific denitrification rate, qDN,max , was found to obtain values, depending on
 the type of the carbon source, between 0,045 and 0,390 gNO3
 --N/(gXHET·d), whereas the
 extremely low value of the half saturation constant for the denitrification process (Km,NO3-N <<
 1mgN/l) indicated its description by zero order kinetics. The maximum specific nitrification
 rate, qN,max, was determined to vary in a narrow frame, between 1,28 and 1,60 gNH4
 +-
 N/(gXAO·d). The half saturation constant for the nitrification process, Km,NH4-N, was estimated
 graphically at 3,1 – 6,1 gNH4
 +-N l-1, corresponding to 62 – 122 μgNH3-N l-1. These values are
 considered to be in good agreement with the literature.
 The determination of kinetic parameters can be considered as a useful tool for the process
 design, operation and improvement of wastewater treatment plants. Furthermore, the study of
 the biological process kinetics contributes to the better understanding and outline of the
 complicated biological processes that contemporarily take place within the various phases of
 BNR wastewater treatment plants.

Long term operation of pilot-scale biological nutrient removal process in treating municipal wastewater

The performance of a pilot-scale biological nutrient removal process has been evaluated for 336 days, receiving the real municipal wastewater with a flowrate of 6.8 m 3/d. The process incorporated an intermittent aeration reactor for enhancing the effluent quality, and a nitrification reactor packed with the porous polyurethane foam media for supporting the attached-growth of microorganism responsible for nitrification. The observation shows that the process enabled a relatively stable and high performance in both organics and nutrient removals. When the SRT was maintained at 12 days, COD, nitrogen, and phosphorus removals averaged as high as 89% at a loading rate of 0.42–3.95 kg COD/m 3 d (corresponding to average influent concentration of 304 mg COD/L), 76% at the loading rate of 0.03–0.27 kg N/m 3 d (with 37.1 mg TN/L on average), and 95% at the loading rate of 0.01–0.07 kg TP/m 3 d (with 5.4 mg TP/L on average), respectively.

Simultaneous removal of organic and strong nitrogen from sewage in a pilot-scale BNR process supplemented with food waste

As the sewerage system is incomplete, sewage in Korea lacks easily biodegradable organics for nutrient removal. In this country, about 11,400 tons of food waste of high organic materials is produced daily. Therefore, the potential of food waste as an external carbon source was examined in a pilot-scale BNR (biological nutrient removal) process for a half year. It was found that as the supply of the external carbon increased, the average removal efficiencies of T-N (total nitrogen) and T-P (total phosphorus) increased from 53% and 55% to 97% and 93%, respectively. VFAs (volatile fatty acids) concentration of the external carbon source strongly affected denitrification efficiency and EBPR (enhanced biological phosphorus removal) activity. Biological phosphorus removal was increased to 93% when T-N removal efficiency increased from 78% to 97%. In this study, several kinds of PHAs (poly-hydroxyalkanoates) in cells were observed. The observed PHAs was composed of 37% 3HB (poly-3-hydroxybutyrate), 47% 3HV (poly-3-hydroxyvalerate), 9% 3HH (poly-3-hydroxyhexanoate), 5% 3HO (poly-3-hydroxyoctanoate), and 2% 3HD (poly-3-hydroxydecanoate).

Operational Optimisation of Pilot Scale Biological Nutrient Removal at the Ciudad Real (Spain) Domestic Wastewater Treatment Plant

The aim of this work is optimising operating conditions for a possibleimplementation of a Biological Nutrient Removal (BNR) process in the Wastewater Treatment Plant (WWTP) of Ciudad Real (Spain). Several factors (hydraulic retention times, anaerobic nitrate concentration, sludge age and wastewater biodegradability) were tested using a pilot scale VIP (Virginia Initiative Plant) activated sludge process and domestic wastewater from the full scale plant. Hydraulic retention times used did not cause changes in N and P removal. P removal was adversely affected by anaerobic NO3- and improved with higher BOD5/COD ratios in wastewater. Influence of sludge age was very low in P removal, but N removal was mainly affected by this factor. Final operating conditions were selected taking into account their effects over one of both nutrients. COD and SS removal were always successful. N removal was also easily reached and the main difficulty was P removal. P sludge content was very low (2.5–4%) approximately and was also affected by the same factors tested. The main factor to improve P removal was supposed to be the organic wastewater composition. Wastewater characteristics were modified by using different sources from the WWTP. Volatile fatty acids (VFA) addition to the wastewater by using supernatant of the anaerobic sludge digesters seemed to be the best practical solution for a future BNR implementation in the WWTP.

The biomass fractions of heterotrophs and phosphate-accumulating organisms in a nitrogen and phosphorus removal system

In this study, the biomass fractions of heterotrophs ( X H) and phosphate-accumulating organisms ( X PAO) were estimated through experimental results and theoretical calculation on the mass balance of organic matter, nitrogen and phosphorus in a pilot scale biological nutrient removal process. The process, comprised of conventional anaerobic–anoxic–aerobic activated sludge and a rotating biological contactor in the aerobic stage, was controlled under steady state under conditions of a solid retention time of 10 days and a dissolved oxygen concentration of 2.0 mg/l in the aerobic stage. For long term operation, the process exhibited high performance in organic matter, nitrogen and phosphorus removal. The removal efficiency was 96.5, 70 and 100% of organic matter, total nitrogen and total phosphorus, respectively. According to the mass balance calculation, approximately 62.0% of organic matter, 48.0% of nitrogen and 47.2% of phosphorus of influent were removed in the form of carbon dioxide, nitrogen gas and polyphosphate, respectively. Regarding X H and X PAO as the major organisms responsible for biomass production, the yield fractions of X H growth in anoxic and aerobic conditions were 48.4 and 39.4%, respectively. Moreover, the yield fraction of X PAO growth in aerobic conditions was 12.2%. These results showed that X H was the major community; moreover, only a minute amount of X PAO was present in this nitrogen and phosphorus removal system for municipal wastewater treatment.