Oxidation Ditch Research Articles

Energetic evaluation of wastewater treatment using microalgae, Chlorella vulgaris

This research evaluates the feasibility of utilizing municipal wastewater source as growth medium for microalgae production and wastewater treatment. First, the effect of the addition of external organic carbon on the microalgae growth and wastewater treatment was studied. Second, actual municipal wastewater from two different (primary and secondary) levels of treatment of an oxidation ditch wastewater treatment plant was used as a growth medium to evaluate both the microalgae growth and wastewater treatment. Third, the effect of light under day/night cycles was evaluated using actual municipal wastewater. A comparative analysis of volumetric biomass productivities, specific growth rates and energetic evaluation of the three different experimental conditions was performed. COD removal rates were 37.5 mg/L, 87.5 mg/L, and 118.75 mg/L per day while microalgae volumetric biomass concentrations were approximately 50–80 mg/L per day with specific biomass growth rates of 0.81, 0.89, and 1.28 1/d for 125, 250, and 500 mg/L COD concentrations, respectively. COD removal, biomass production and specific growth rates are lower for the municipal wastewater due to poor availability of carbon source. However, microalgae present a promising alternative when the energetic evaluation is considered for both actual and synthetic wastewater treatment. A total of 13.5, 17.4, and 35.2% of net energy recovery was possible with microalgae harvested in synthetic wastewater at 125, 250, and 500 mg/L COD concentrations, respectively while a total of 4.7% net energy recovery was possible with microalgae harvested in raw wastewater after accounting for the energy required for wastewater treatment.

Seasonal bacterial community succession in four typical wastewater treatment plants: correlations between core microbes and process performance

To understand the seasonal variation of the activated sludge (AS) bacterial community and identify core microbes in different wastewater processing systems, seasonal AS samples were taken from every biological treatment unit within 4 full-scale wastewater treatment plants. These plants adopted A2/O, A/O and oxidation ditch processes and were active in the treatment of different types and sources of wastewater, some domestic and others industrial. The bacterial community composition was analyzed using high-throughput sequencing technology. The correlations among microbial community structure, dominant microbes and process performance were investigated. Seasonal variation had a stronger impact on the AS bacterial community than any variation within different wastewater treatment system. Facing seasonal variation, the bacterial community within the oxidation ditch process remained more stable those in either the A2/O or A/O processes. The core genera in domestic wastewater treatment systems were Nitrospira, Caldilineaceae, Pseudomonas and Lactococcus. The core genera in the textile dyeing and fine chemical industrial wastewater treatment systems were Nitrospira, Thauera and Thiobacillus.

Intestinal bacteria in bioaerosols and factors affecting their survival in two oxidation ditch process municipal wastewater treatment plants located in different regions

Samples from two oxidation ditch process municipal wastewater treatment plants (MWTPs) (HJK and GXQ) in two regions of China were analysed for bacteria, particles, total organic carbon, and water-soluble ions in bioaerosols. Diversity and potential pathogen populations were evaluated by high-throughput sequencing. Bioaerosol sources, factors affecting intestinal bacterial survival, and the relationship between bioaerosols and water were analysed by Source tracker and partial least squares-discriminant, principal component, and canonical correspondence analyses. Culturable bacteria concentrations were 110–846 and 27–579 CFU/m3 at HJK and GXQ, respectively. Intestinal bacteria constituted 6–33% of bacteria. Biochemical reaction tank, sludge dewatering house (SDH), and fine screen samples showed the greatest contribution to bioaerosol contamination. Enterobacter aerogenes was the main intestinal bacteria (> 99.5%) in HJK and detected at each sampling site. Enterobacter aerogenes (98.67% in SDH), Aeromonas sp. (76.3% in biochemical reaction tank), and Acinetobacter baumannii (99.89% in fine screens) were the main intestinal bacteria in GXQ. Total suspended particulate masses in SDH were 229.46 and 141.6 μg/m3 in HJK and GXQ, respectively. Percentages of insoluble compounds in total suspended particulates decreased as height increased. The main soluble ions in bioaerosols were Ca2+, Na+, Cl-, and SO42-, which ranged from 3.8 to 27.55 μg/m3 in the MWTPs. Water was a main source of intestinal bacteria in bioaerosols from the MWTPs. Bioaerosols in HJK but not in GXQ were closely related. Relative humidity and some ions positively influenced intestinal bacteria in bioaerosols, while wind speed and solar illumination had a negative influence.

Comprehensive evaluation of the main technology for new sewage treatment plants in small towns along the Duliujian river basin

In recent years, water contamination problem has been becoming more and more serious due to increasing wastewater discharge. So our country has accelerated the pace of constructing sewage treatment plant in small towns. But in China it has not been issued any corresponding technical specifications about the choice of treatment technology. So the article is based on the basin of Duliujian river, through field research, data collection and analysis of relevant documentations, preliminarily elects seven kinds of technology: Improved A2/O, Integrated oxidation ditch, Orbal oxidation ditch, CASS, A/O+refined diatomite, BIOLAK and UNITANK as alternatives for Tianjin sewage discharge local standard.Then the article use the analytic hierarchy process (AHP) to evaluate the seven kinds of alternatives, finally it is concluded that CASS technology is most suitable for the main technology of new sewage treatment plants in small towns along the Duliujian River basin.

Fate of artificial sweeteners through wastewater treatment plants and water treatment processes.

Five full-scale wastewater treatment plants (WWTPs) in China using typical biodegradation processes (SBR, oxidation ditch, A2/O) were selected to assess the removal of four popular artificial sweeteners (ASs). All four ASs (acesulfame (ACE), sucralose (SUC), cyclamate (CYC) and saccharin (SAC)) were detected, ranging from 0.43 to 27.34μg/L in the influent. Higher concentrations of ASs were measured in winter. ACE could be partly removed by 7.11–50.76% through biodegradation and especially through the denitrifying process. The A2/O process was the most efficient at biodegrading ASs. Adsorption (by granular activated carbon (GAC) and magnetic resin) and ultraviolet radiation-based advanced oxidation processes (UV/AOPs) were evaluated to remove ASs in laboratory-scale tests. The amounts of resin adsorbed were 3.33–18.51 times more than those of GAC except for SUC. The adsorption ability of resin decreased in the order of SAC > ACE > CYC > SUC in accordance with the pKa. Degradation of ASs followed pseudo-first-order kinetics in UV/H2O2 and UV/PDS. When applied to the secondary effluent, ASs could be degraded from 30.87 to 99.93% using UV/PDS in 30 minutes and UV/PDS was more efficient and economic.

CFD method for the relationship between the radius size of impellers and cross-sectional average velocity of flow in an oxidation ditch

CFD method for the relationship between the radius size of impellers and cross-sectional average velocity of flow in an oxidation ditch

Performance Evaluation and Dissolved Oxygen Effect in Deep-bed Denitrification Filter: a Full-scale Plant Case Study

The aims of this study were twofold. Firstly, the denitrificaion performance in deep-bed denitrificaiton filter (DBDF), serving as the advanced total nitrogen (TN) and total phosphorus (TP) removal technology, was evaluated. Secondly, the effect of dissolved oxygen (DO) into the DBDF on both the denitrificaion performance and the external carbon source addition was investigated. The operational results over eight months demonstrated good TN removal efficiency (87.8%) in the studied full-scale plant, in which 70.7% and 17.1% of TN were removed in the pre-denitrifation in oxidation ditch and post-denitrifation in DBDF, respectively. The DO concentration was inversely related to both the external carbon source dosage and the nitrate removed in DBDF. A dose of 3.60Kg methane (97%) was required to remove 1Kg nitrate, with approximately 26.2% of methane dosed was depleted by the DO in DBDF influent. It is suggested to take some measures to eliminate or mitigate the waterfall reoxygenation at process configurations before the DBDF, which is expected to save the cost of external carbon source.

Stochastic evolutionary-based optimization for rapid diagnosis and energy-saving in pilot- and full-scale Carrousel oxidation ditches

Energy consumption is a primary issue needed to be considered for wastewater treatment targeting qualified effluent. In this paper, a hybrid model is proposed for rapid diagnosis of operational conditions meeting requirements of discharge standards and energy saving in Carrousel Oxidation Ditches (ODs). Based on a three-dimensional (3D) three-phase computational fluid dynamics (CFD) model, we developed an artificial neural network (ANN) model with back propagation algorithm and an accelerating genetic algorithm (AGA) model to achieve real-time simulation and system optimization in the Carrousel ODs. By incorporating the 3D-CFD and multi-site ANN models, the hybrid model provided reasonable predictions of liquid flow, sludge sedimentation and water quality in the Carrousel ODs. With help of the AGA model based on evolution theory, system optimization could be reached to meet multiple purposes such as energy saving, water-quality improving and normal sludge distribution, which was successfully demonstrated in both pilot- and full-scale Carrousel ODs.

CFD method for the liquid–gas two-phase flow fields in an Orbal oxidation ditch

CFD method for the liquid–gas two-phase flow fields in an Orbal oxidation ditch

Ammonia-Based Aeration Control of an Oxidation Ditch to Improve Effluent Quality and Reduce Operating Cost

Ammonia-Based Aeration Control of an Oxidation Ditch to Improve Effluent Quality and Reduce Operating Cost

Simulation of effective volume increasement inside oxidation ditch reactor

Oxidation ditch reactor is wastewater treatment unit that based on activated sludge process. Water flow characteristic inside reactor is either completely-mixed reactor or plug flow reactor. Water flow characterization plays important role in wastewater treatment process. To ensure the biological process going well, the water flow in reactor must be completely mixed type. Characterization study of water flow in reactor consume time thus financial, so the simulation using CFD (Computational Fluid Dynamics) becomes a good solution. Based on the calibrated model, the CFD simulation was generate to define the water flow characteristic of the oxidation ditch reactor in longitudinal section. The simulation was conducted using VoF (Volume of Fluid) scheme, an open surface model in unsteady flow with k-ε turbulence model. The simulation result shows that water flow inside the oxidation ditch reactor was plug flow. The role of aeration system is to increase water flow to be more homogen, indicated by higher effective volume inside the reactor. The simulation result shows that the aerator could increase effective volume inside the reactor from 32,94% into 55,5%. The higher effective volume means dead zone inside the reactor is reduced.

Use of Alum for Odor Reduction in Sludge and Biosolids from Different Wastewater Treatment Processes.

Applicability of alum addition to wastewater sludge and biosolids produced from different treatment processes was evaluated as a means of odor reduction. Four water resource recovery facilities (WRRFs) were chosen for this study: two used mesophilic anaerobic digestion and two used oxidation ditch processes. The experiments were conducted on a laboratory scale and in all cases the alum was added prior to dewatering. This is the first report of the application of alum for odor reduction in oxidation ditch processes. Alum addition was effective in reducing odors in anaerobically digested biosolids. Addition of 4% alum to anaerobically digested liquid biosolids prior to dewatering resulted in a 60% reduction in the peak odor concentration in the laboratory dewatered cake, relative to the control sample. Alum addition did not reduce odors in dewatered sludge from oxidation ditch processes.

Investigating the performance of three modified activated sludge processes treating municipal wastewater in organic pollutants removal and toxicity reduction

This study investigated the treatment performance of three types of modified activated sludge processes, i.e., anoxic/oxic (A/O), anaerobic/anoxic/oxic (A2/O) and oxidation ditch process, in treating municipal wastewater by measuring physicochemical and spectroscopic parameters, and the toxicity of the influents and effluents collected from 8 full-scale municipal wastewater treatment plants (MWTPs). The relationships between spectroscopic and physicochemical parameters of the wastewater samples and the applicability of the nematode Caenorhabditis elegans (C. elegans) bioassays for the assessment of the toxic properties of municipal wastewater were also evaluated. The results indicated that the investigated MWTPs employing any of A/O, A2/O and oxidation ditch processes could effectively control the discharge of major wastewater pollutants including biochemical oxygen demand (BOD), chemical oxygen demand, nitrogen and phosphorus. The oxidation ditch process appeared to have the advantage of removing tyrosine-like substances and presented slightly better removal efficiency of tryptophan-like fluorescent (peak T) substances than the A/O and A2/O processes. Both ultraviolet absorbance at 254nm and peak T may be used to characterize the organic load of municipal wastewater, and peak T can be adopted as a gauge of the BOD removal efficacy of municipal wastewater treatment. Using C. elegans-based oxygen consumption rate assay for monitoring municipal wastewater toxicity deserves further investigations.

The comparison of greenhouse gas emissions in sewage treatment plants with different treatment processes

Greenhouse gas emissions from different sewage treatment plants: oxidation ditch process, double-circulated anoxic-oxic process and anoxic-oxic process were evaluated based on the survey. The methane and nitrous oxide characteristics were discussed based on the gaseous and dissolved gas profiles. As a result, it was found that methane was produced in the sewer pipes and the primary sedimentation tank. Additionally, a ventilation system would promote the gasification of dissolved methane in the first treatment units. Nitrous oxide was produced and emitted in oxic tanks with nitrite accumulation inside the sewage treatment plant. A certain amount of nitrous oxide was also discharged as dissolved gas through the effluent water. If the amount of dissolved nitrous oxide discharge is not included, 7–14% of total nitrous oxide emission would be overlooked. Based on the greenhouse gas calculation, electrical consumption and the N2O emission from incineration process were major sources in all the plants. For greenhouse gas reduction, oxidation ditch process has an advantage over the other advanced systems due to lower energy consumption, sludge production, and nitrogen removal without gas stripping.

Community structures and population dynamics of “Candidatus Accumulibacter” in activated sludges of wastewater treatment plants using ppk1 as phylogenetic marker

Candidatus Accumulibacter has been identified as dominant polyphosphate-accumulating organisms (PAOs) in enhanced biological phosphorus (P) removal (EBPR) from wastewater. This study revealed the relevance of community structure, abundance and seasonal population dynamics of Candidatus Accumulibacter to process operation of wastewater treatment plants (WWTPs) in China using ppk1 gene as phylogenetic marker. All sludge samples had properties of denitrifying P removal using nitrate as an electron acceptor. Accumulibacter abundance in the anaerobic-anoxic-oxic (A2O) process was the highest (26% of total bacteria), and higher in winter than in summer with a better EBPR performance. Type-II was the dominant Accumulibacter in all processes, and type-I accounted for a small proportion of total Accumulibacter. The abundance of Clade-IIC as the most dominant clade reached 2.59×109 cells/g MLSS and accounted for 87.3% of total Accumulibacter. Clade IIC mainly contributed to denitrifying P removal. Clades IIA, IIC and IID were found in all processes, while clade-IIF was only found in oxidation ditch process through phylogenetic analysis. High proportion of clade IID to total Accumulibacter led to poor performance of aerobic P-uptake in inverted A2O process. Therefore, Accumulibacter clades in WWTPs were diverse, and EBPR performance was closely related to the clade-level community structures and abundances of Accumulibacter.

Composition, Evolution, and Complexation of Dissolved Organic Matter with Heavy Metals in Landfills

Samples of wastes and leachates were collected from a landfill site and a leachate treatment plant[i.e., equalization basin, anaerobic zone, oxidation ditch, and membrane bioreactor (MBR) section]. Dissolved organic matter (DOM) was extracted from the wastes and leachates, and its composition, evolution, and complexation characteristics with heavy metals were studied using UV-Visible and fluorescence spectroscopy combined with1H nuclear magnetic resonance. The aliphatic compounds were found to be the main substances in DOM in the fresh landfill wastes (<5 a), and the relative content of aromatics and substituent groups, i.e., carbonyl, hydroxyl, and carboxyl functional groups, decreased during the initial process. On the other hand, carbohydrates and organic amines were observed to be the main substances in DOM obtained from the intermediate and old landfill wastes (>5 a), and the relative content of aromatics and substituent groups (carbonyl, hydroxyl, and carboxyl functional groups) increased persistently during the process of organic matter humification. The aliphatics, carbohydrates, and organic amines all existed in DOM from the equalization basin Carbohydrates and aromatic compounds increased rapidly after the anaerobic, aerobiotic, and membrane treatment. However, low molecular weight organic matter and alkyl chain substances decreased during the leachate treatment process and the side chain of the aliphatics was shortened despite the increase in its content. The distribution of zinc in the wastes and leachates was influenced by the complexation with the nitrogen-and oxygen-containing functional groups, whose effect on other metals was not obvious.

Evaluation of the process performance of a down-flow hanging sponge reactor for direct treatment of domestic wastewater in Bangkok, Thailand

ABSTRACTThis study assesses the performance of an aerobic trickling filter, down-flow hanging sponge (DHS) reactor, as a decentralized domestic wastewater treatment technology. Also, the characteristic eukaryotic community structure in DHS reactor was investigated. Long-term operation of a DHS reactor for direct treatment of domestic wastewater (COD = 150–170 mg/L and BOD = 60–90 mg/L) was performed under the average ambient temperature ranged from 28°C to 31°C in Bangkok, Thailand. Throughout the evaluation period of 550 days, the DHS reactor at a hydraulic retention time of 3 h showed better performance than the existing oxidation ditch process in the removal of organic carbon (COD removal rate = 80–83% and BOD removal rate = 91%), nitrogen compounds (total nitrogen removal rate = 45–51% and NH4+–N removal rate = 95–98%), and low excess sludge production (0.04 gTS/gCOD removed). The clone library based on the 18S ribosomal ribonucleic acid gene sequence revealed that phylogenetic diversity of 18S rRNA gene in the DHS reactor was higher than that of the present oxidation ditch process. Furthermore, the DHS reactor also demonstrated sufficient COD and NH4+–N removal efficiency under flow rate fluctuation conditions that simulates a small-scale treatment facility. The results show that a DHS reactor could be applied as a decentralized domestic wastewater treatment technology in tropical regions such as Bangkok, Thailand.

Wastewater treatment facility upgrade uses combination of technologies to solve nutrient removal challenges

New regulations required the 7.5 ML/d North East River Advanced Wastewater Treatment Facility to upgrade to meet lower annual average effluent nitrogen and phosphorus limits. At the same time, facility planning was underway to expand the facility to 17.0 ML/d to accommodate planned growth in the service area. Following a pilot study to establish the performance capabilities of the existing process and a technology alternatives evaluation, a combination of a Carrousel® 5-stage oxidation ditches followed by a membrane filtration system was used to convert the facility to a membrane bioreactor. This combination of technologies is unique among the more than 300 facilities recently upgraded for nutrient removal in the Chesapeake Bay region. The new process went into service in late 2015 and has demonstrated the ability to meet effluent performance requirements for total nitrogen and total phosphorus.

Multi-criteria group decision-making based sustainability measurement of wastewater treatment processes

There are various processes which can be used for wastewater treatment (WT), and the selection of the most sustainable one among different processes is a hard task. This study aims at helping the decision-makers (DM) to address this by developing an intuitionistic fuzzy set (IFS) theory based group multi-attribute decision analysis (MADA) method. Ten criteria in environment, economy, society-politic, and technology dimensions were employed to achieve sustainability measurement (SM) of WT processes. The multi-criteria sustainability assessment method developed in this study allow different experts to attend the SM, and enable the participants to employ the natural language/words to depict their intuitionistic opinions. Accordingly, the proposed method can achieve group SM under uncertainties. An illustrative case including four processes for wastewater treatment, namely Anaerobic-Anoxic-Oxic (AAO) process, Triple Oxidation Ditch (TOD) process, Anaerobic single-ditch oxidation (ASD) process, and Sequencing batch reactor activated sludge process (SBR), has been studied, and the results reveal that this method can determine sustainability sequence of different WT processes.

Removal of Estrogenic Effect by Typical Domestic Wastewater Treatment Processes

Targeting at the characteristics of low concentration but high risk of endocrine disrupting compounds in the aquatic environment, the current study investigated the distribution of estrogenicity and E2 level using recombinant yeast estrogen screen (YES) and enzyme linked immunosorbent assay (ELSIA) during domestic wastewater treatment processes. The results showed that the levels of estrogenicity and E2 in influents of wastewater treatment plants were 4.35-7.58 ng·L-1 and 36.95-83.43 ng·L-1, respectively. It was found that biological treatment processes played a crucial role in the removal of estrogenicity and E2, such as oxidation ditch, A2/O and A2/O followed by MBR, where the removal of estrogenicity and E2 was 71.10%-75.54% and 75.88%-80.72%, respectively. The activated sludge, with an estrogencity level of 1.84-2.43 ng·g-1 and an E2 level of 8.45-12.84 ng·g-1, had the function of eliminating estrogenic effect to a certain extent by adsorption. The estrogenic activity in the effluent of domestic wastewater was 1.06-2.19 ng·L-1, which will pose potential risk to the aquatic life in the environment. Last but not least, ELISA had a good correlation with YES assay, which provides a new method for rapid screening and assessment of water environmental estrogen.