Extended Aeration Treatment Research Articles

Performance evaluation of an extended aeration treatment plant: a case study in Sarawak, Malaysia

Performance evaluation of an extended aeration treatment plant: a case study in Sarawak, Malaysia

Performance evaluation of an extended aeration treatment plant (EATP): A case study in Sarawak, Malaysia

Performance evaluation of an extended aeration treatment plant (EATP): A case study in Sarawak, Malaysia

A multi-criteria GIS model for suitability analysis of locations of decentralized wastewater treatment units: case study in Sulaimania, Iraq

Sulaimania is a City located in Kurdistan region in the north of Iraq. The city is facing a lack of water, and it will reach a very critical condition shortly. One of the potential solutions is to reuse the treated wastewater for non-direct human uses such as irrigation, washing, firefighting, groundwater recharging, and others. There is no sewage treatment plant in the city. The wastewater flows into a stream through some sewer outlets, and that causes big environmental issues. Decentralized wastewater treatment units (DTUs) are suggested to solve the issue. The treated wastewater will be used for the irrigation of the green areas of the city. The selected plant type is Extended Aeration treatment system, which is recommended for residential areas. Specifying the locations of the treatment units is very important from environmental, social and technical aspects. The main objective of this study is to select the best suitable places for the DTUs. Preliminary selections of 134 nominated areas for DTU locations were made in different places in the city. The locations are distributed into 10 groups near the main sewer pipes of the city. A model is created to evaluate those selected locations and eliminate the non-suitable locations by using GIS software integrated with the Analytical Hierarchy Process (AHP). Five criteria were used in the model, which are, (1) The size of the available lands, (2) The distance from the decentralized units to the green areas (3) Population density around the decentralized treatment unit locations, (4) The slope of the land and (5) Depth of the main sewer pipe at the nominated area. In addition, the model adopted two restriction factors, which are: (1) The distance from the decentralized treatment unit to the buildings should not be less than 10 m and (2) The distance between the main sewer pipes and the treatment units are taken to be <50 m. The results of the suitability analysis produced six classes of suitability levels of the nominated areas started from restricted to extremely suitable. The suitability percentages of the 6 classes of the total nominated areas were found to be; 8.5% (6.95 ha) restricted, 0.4 % (0.23 ha) moderately suitable, 12.8% (10.50 ha) suitable, 38.8% very suitable (31.60 ha), 32.2% (26.33 ha) highly suitable and 7.3% (5.92 ha) extremely suitable. Each nominated area has more than one suitability class. Normalized Weighted Average (NWAV) of the suitability level percentage of each nominated area is found. The values of the NWAV are ranged from 0.0 to 1.0, and the selection of final DTUs locations will be for areas that have NWAV larger than 0.5. Optimum 30 suitable locations are selected out of the 134 nominated areas.

Cost comparison of full-scale water reclamation technologies with an emphasis on membrane bioreactors.

The paper assesses the costs of full-scale membrane bioreactors (MBRs). Capital expenditures (CAPEX) and operating expenses (OPEX) of Spanish MBR facilities have been verified and compared to activated sludge plants (CAS) using water reclamation treatment (both conventional and advanced). Spanish MBR facilities require a production of 0.6 to 1.2 kWh per m3, while extended aeration (EA) and advanced reclamation treatment require 1.2 kWh per m3. The energy represents around 40% of the OPEX in MBRs. In terms of CAPEX, the implementation costs of a CAS facility followed by conventional water reclamation treatment (physical-chemical + sand filtration + disinfection) ranged from 730 to 850 €.m-3d, and from 1,050 to 1,250 €.m-3d in the case of advanced reclamation treatment facilities (membrane filtration) with a capacity of 8,000 to 15,000 m3d-1. The MBR cost for similar capacities ranges between 700 and 960 €.m-3d. This study shows that MBRs that have been recently installed represent a cost competitive option for water reuse applications for medium and large capacities (over 10,000 m3d-1), with similar OPEX to EA and conventional water reclamation treatment. In terms of CAPEX, MBRs are cheaper than EA, followed by advanced water reclamation treatment.

Conditioning the alternating aerobic–anoxic process to enhance the removal of inorganic nitrogen pollution from a municipal wastewater in France

Inorganic nitrogen pollution from surface waters can adversely affect human health and the environment. Coupled nitrification–denitrification can significantly remove the total inorganic nitrogen pollution amount from municipal wastewater; however, researchers only have a limited understanding of the alternating aerobic–anoxic process in a single reactor. This study performed a typical treatment using a completely mixed alternating aerobic–anoxic extended aeration treatment process in a single reactor, biological fluidised bed reactor to remove inorganic nitrogen pollution from a municipal wastewater in France. Comparative analysis of the coupled nitrification–denitrification reactions was carried out to investigate the two different alternating aerobic–anoxic processes of 3-h aerobic digestion and 6-h anoxic time and 3-h aerobic digestion and 3-h anoxic time. The results indicate that the change in anoxic time, specifically, from 6 to 3 h, can increase the alternating aerobic–anoxic process performance by approximately 53.4%. The average effluent inorganic nitrogen concentration decreased from 10.3 to 4.8 mg N/L, achieving the desired inorganic nitrogen concentration of less than 10 mg N/L in the outflow to meet the stringent effluent standards. The study offers a proper treatment that can be used to help reduce inorganic nitrogen pollution from municipal wastewater processed in a single-sludge reactor. The study's results advance the understanding of this simple technique that effectively removes inorganic nitrogen pollution from municipal wastewater.

Model to Quantify Removal and Inactivation of Microorganisms Occluded in Effluent Wastewater Particles Using Filtration and Disinfection Systems

A model is presented to quantify microbial occlusion in effluent particles and improve understanding of the removal and inactivation of occluded microorganisms in filtration and disinfection systems. Microbial occlusion in particles is described in the model as a function of the particle size distribution, the microbial density ( N1 ) , which is the average quantity of target microorganisms within the subset of particles that contain microorganisms, and the frequency of association ( N2 ) , which is the ratio of particles that contain at least one target microorganism. To demonstrate the model, undisinfected secondary effluent samples were collected from an extended aeration treatment facility and analyzed to determine values for the model variables, N1 and N2 for heterotrophic bacteria and aerobic endospores and N2 for total coliform bacteria. Heterotrophic bacteria were present in most effluent particles (73–100%) at high densities (7–93 per particle), whereas aerobic endospores and total coliform bacte...

Reuse of treated sewage in Delhi city: Microbial evaluation of STPs and reuse options

Microbiological quality of the treated wastewater is an important parameter for its reuse. The data on the Fecal Coliform (FC) and Fecal Streptococcus (FS) at different stages of treatment in the Sewage Treatment Plants (STPs) in Delhi watershed is not available, therefore in the present study microbial profiling of STPs was carried out to assess the effluent quality for present and future reuse options. This study further evaluates the water quality profiles at different stages of treatment for l6 STPs in Delhi city. These STPs are based on conventional Activated Sludge Process (ASP), extended aeration, physical, chemical and biological treatment (BIOFORE), Trickling Filter and Oxidation Pond. The primary effluent quality produced from most of the STPs was suitable for Soil Aquifer Treatment (SAT). Extended Hydraulic Retention Time (HRT) as a result of low inflow to the STPs was responsible for high turbidity, COD and BOD 5 removal. Conventional ASP based STPs achieved 1.66 log FC and 1.06 log FS removal. STPs with extended aeration treatment process produced better quality effluent with maximum 4 log order reduction in FC and FS levels. “Kondli” and “Nilothi” STPs employing ASP, produced better quality secondary effluent as compared to other STPs based on similar treatment process. Oxidation Pond based STPs showed better FC and FS removals, whereas good physiochemical quality was achieved during the first half of the treatment. Based upon physical, chemical and microbiological removal efficiencies, actual integrated efficiency (IE a) of each STP was determined to evaluate its suitability for reuse for irrigation purposes. Except “Mehrauli” and “Oxidation Pond”, effluents from all other STPs require tertiary treatment for further reuse. Possible reuse options, depending upon the geographical location, proximity of facilities of potential users based on the beneficial uses, and sub-soil types, etc. for the Delhi city have been investigated, which include artificial groundwater recharge, aquaculture, horticulture and industrial uses such as floor washing, boiler feed, and cooling towers, etc.

Removal of refractory organics and color in pigment wastewater with Fenton oxidation

This study was designed to evaluate (1) the removal of the non-biodegradable organics and color by Fenton's oxidation (2) the feasibility of Fenton's oxidation as a pretreatment or tertiary treatment following the activated sludge process in the pigment wastewater. The study was divided into two parts. The first part consisted of investigations on raw Yellow wastewater and Red wastewater, the second part was carried out on the final effluent from the existing extended aeration treatment plant. The batch test was conducted to determine the optimum conditions for plant operation such as pH, H2O2 dosage, molar ratio of Fe2+/H2O2 and contact time. It was found that the removal efficiencies of COD were 54.2%, 52.6% and 58.9%, the removal efficiencies of the color were 91.2%, 18.1% and 45.7%, for Red, Yellow Wastewater and Final Effluent, respectively. In the Yellow wastewater, BOD5COD ratio was not changed much after Fenton's oxidation, but in the case of the Red wastewater, BOD5COD ratio was increased from 0.04 to 0.36. Therefore Fenton's oxidation process is a very effective means for a pretreatment or tertiary treatment in the Pigment wastewater.

Removal of refractory organics and color in pigment wastewater with Fenton oxidation

This study was designed to evaluate (1) the removal of the non-biodegradable organics and color by Fenton's oxidation (2) the feasibility of Fenton's oxidation as a pretreatment or tertiary treatment following the activated sludge process in the pigment wastewater. The study was divided into two parts. The first part consisted of investigations on raw Yellow wastewater and Red wastewater, the second part was carried out on the final effluent from the existing extended aeration treatment plant. The batch test was conducted to determine the optimum conditions for plant operation such as pH, H2O2 dosage, molar ratio of Fe2+H2O2 and contact time. It was found that the removal efficiencies of COD were 54.2%, 52.6% and 58.9%, the removal efficiencies of the color were 91.2%, 18.1% and 45.7%, for Red, Yellow Wastewater and Final Effluent, respectively. In the Yellow wastewater, BOD5/COD ratio was not changed much after Fenton's oxidation, but in the case of the Red wastewater, BOD5/COD ratio was increased from 0.04 to 0.36. Therefore Fenton's oxidation process is a very effective means for a pretreatment or tertiary treatment in the Pigment wastewater.

Enhanced nutrient removal by oxidation-reduction potential (ORP) controlled aeration in a laboratory scale extended aeration treatment system

Two laboratory scale extended aeration treatment systems (EATS) were built to study their nutrient removal performance before and after the introduction of oxidation-reduction potential (ORP) controlled aeration. Effects of various ORP set points (40, 70, 110 and 180 mV) and zoning of the aeration tank (AT) were examined. Each system had a 901 aeration tank and the operating HRT and SRT were 20 h and 20 days, respectively. Synthetic wastewater was used and the F/M ratios ranged from 0.13 to 0.15 gCOD/gMLSS/d. All experimental runs including the control yielded a similar COD removal efficiency of 96.4 ± 0.4% and an effluent COD of 14.4 ± 1.3 mg. This indicates that ORP controlled aeration had no significant impact on the carbonaceous removal of the EATS. Very good nitrogen (N) and phosphorus (P) removal was obtained when there was a small anoxic selector (3.8 l) at the head of the AT and the tank zoned into a main ORP zone (72 l) followed by an aerobic zone (18 l). The selector was found very useful in the prevention and curing of bulking as well as in the removal of P. It effectively denitrified the nitrate from the return sludge stream and caused significant P release, that is important to subsequent P uptake in the ORP and aerobic zones. An optimum ORP set point of 110 mV was found. The aeration pattern was characterized by having an equal time length of aeration and non-aeration. The achievable total nitrogen (TN) removal was 93% with a residual TN of only 2.94 mg/l (N). Excellent P removal of 99.5 ± 0.1% was attained under an ORP set point range of 70–180 mV. P was reduced to 0.05 ± 0.01 mg/l (P) in the effluent.

Enhanced nutrient removal by oxidation-reduction potential (ORP) control in laboratory-scale extended aeration reactors

A study was conducted to examine N and P removal by a laboratory-scale extended aeration treatment system employing oxidation-reduction potential (ORP) controlled aeration. The system was provided with a 90-L aeration tank. When ORP controlled aeration was applied, the aeration tank was divided into three zones, namely the ORP zone (45 L), the anaerobic zone (27 L) and the aerobic zone (18 L). An external anoxic selector of 3.8 L in volume was also added. An ORP set point of 70 mV was used for the ORP zone. The extended aeration treatment system operating without the ORP controlled aeration was used as the control. COD removal (97%) was not affected, but both N and P removal were enhanced significantly in the ORP reactor. Total N removal efficiency was increased from 49.1% (control) to 83.5%. Almost all P was captured (99%), leaving an average of 0.09 mg L −1 P in the effluent. The ORP reactor yielded a sludge P content of 3.1%, compared to only 1.8% for the control. This indicated luxury P uptake in ORP reactor. Very significant P release and denitrification were found in the anoxic selector. Fairly good simultaneous nitrification and denitrification had occurred in the ORP zone. However, P release was very limited in the anoxic zone. However, anoxic P uptake and nitrification were found in this zone. Low F/M bulking was observed in both the control and ORP operation before the installation of a selector. Bacterial Type 0041 was identified as the predominant bulking organism. For the Control, an aerobic selector cured the bulking problem in one sludge age while an anoxic selector fixed up the problem during the ORP operation.

Pilot-Scale Studies on Extended Aeration at Fermentor Fill

This study examined the effects of oxygen supplementation on fermentation performance. Two types of fermentations were performed in 6-gal. pilot-scale fermentors: 1) wort was aerated to saturation and pitched; 2) wort was aerated to saturation, pitched, and given additional air for 6 hr. The fermentations were monitored through primary and secondary stages. Several parameters were examined: yeast count, extract, alcohol concentration, degree of fermentation, and pH. The fermentations with extended aeration were somewhat more vigorous during primary fermentation and had a lower pH. By the end of secondary fermentation, the differences observed were reduced; however, the pH remained substantially lower with extended aeration. Pyruvic acid in the finished beer was considerably higher under extended aeration, whereas sulfur dioxide and acetaldehyde were lower. Flavor evaluation showed preference for the extended aeration treatment.

Pilot-Scale Studies on Extended Aeration at Fermentor Fill

This study examined the effects of oxygen supplementation on fermentation performance. Two types of fermentations were performed in 6-gal. pilot-scale fermentors: 1) wort was aerated to saturation and pitched; 2) wort was aerated to saturation, pitched, and given additional air for 6 hr. The fermentations were monitored through primary and secondary stages. Several parameters were examined: yeast count, extract, alcohol concentration, degree of fermentation, and pH. The fermentations with extended aeration were somewhat more vigorous during primary fermentation and had a lower pH. By the end of secondary fermentation, the differences observed were reduced; however, the pH remained substantially lower with extended aeration. Pyruvic acid in the finished beer was considerably higher under extended aeration, whereas sulfur dioxide and acetaldehyde were lower. Flavor evaluation showed preference for the extended aeration treatment.

Long term BOD determinations on biologically treated and untreated kraft mill effluent discharged to Lake Saimaa, Finland

Long-term BOD determinations have been carried out on kraft pulp mill effluent over a period of more than 200 days using the conventional dilution method and utilizing a special bottle sealing technique. Determinations were made at the temperatures 2, 5, 10 and 20°C on untreated effluent and on effluent treated by an experimental biological extended aeration treatment plant which treated effluent discharged to Lake Saimaa in eastern Finland. BOD curves have been constructed for up to a period of 200 days and the results indicate that untreated effluent exerts a two-stage BOD on receiving waters, the second stage commencing after approx. 28 days. Treated effluent was found to have a low BOD and showed no second stage of oxygen uptake.