Oxidation Ditch Process Research Articles

Jilin city central wastewater treatment plant renovation design scheme

Jilin City is one of the top ten famous Chinese cities worth introducing to the world. To further improve the construction of urban infrastructure and meet the needs of the economic and social development of Jilin City, the Jilin City Government Joint Development and Reform Commission and the Ecological Environment Bureau decided to expand and renovate the former Jilin City wastewater treatment plant. This study designs a wastewater treatment plant by comprehensively considering the policy needs and the local basic background characteristics of Jilin to solve the wastewater overflow problem. The design modified the anaerobic tank and Carroussel oxidation ditch processes, which have more advantages than traditional treatment processes, mainly including better BOD, nitrogen and phosphorus removal efficiency, less power consumption, and lower operating costs. This treatment plant design contains two special characteristics: the design considers the overall plan and pipeline layout of the wastewater treatment plant, and the size data of each module are calculated through theoretical study conforming to the real case.

Understanding microplastic presence in different wastewater treatment processes: Removal efficiency and source identification

Municipal effluents discharged from wastewater treatment plants (WWTPs) are a considerable source of microplastics in the environment. The dynamic profiles of microplastics in treatment units in WWTPs with different treatment processes remain unclear. This study quantitatively analyzed microplastics in wastewater samples collected from different treatment units in two tertiary treatment plants with distinct processes. The influents contained an average of 15.5 ± 3.5 particles/L and 38.5 ± 2.5 particles/L in the two WWTPs with in the oxidation ditch process and the integrated fixed-film activated sludge process, respectively. Interestingly, microplastic concentrations in the influent were more influenced by the population density in the served area than sewage volume or served population equivalent. Throughout the treatment process, concentrations were reduced to 1.5 ± 0.5 particles/L and 1.0 ± 1.0 particles/L in the final effluents, representing an overall decrease of 90% and 97%, in WWTPs with the oxidation ditch process and integrated fixed-film activated sludge process, respectively. A significant proportion of the microplastics were removed during the primary treatment stage in both WWTPs, with better performance for foam, film, line-shaped and large-sized microplastics. Most microplastics were accumulated in activated sludge, indicating its key role as the primary sink in WWTPs. The multiple correspondence analysis identified laundry washing and daily necessities such as packaging and containers as the major contributors to microplastics in WWTPs. The study proposed recommendations for upgrading WWTPs, modifying designs, and implementing strategies to reduce microplastic sources, aiming to minimize the release of microplastics into the environment. These findings can shed lights on the sources of microplastics in WWTPs, and advance our understanding of the mechanisms for more effective microplastic removals in wastewater treatment technologies in future applications.

Effects of alternative disinfection methods on the characteristics of effluent organic matter and the formation of disinfection byproducts

The characteristics of effluent organic matter (EfOM) and the type of disinfection methods are closely related to the formation of disinfection byproducts (DBPs) in reclaimed water. In this study, five disinfection methods, i.e., chlorination, ultraviolet (UV) followed by chlorination (UV + Cl), UV/chlorine (UV/Cl), chloramination, and chlorine dioxide (ClO2), were applied to investigate the changes in the properties of EfOM, the formation of DBPs, and the relationship between EfOM properties and DBP formation during the disinfection of four secondary biological effluents. The results showed that EfOM with medium molecular weight (MW) (0.5–6 kDa) was the dominant fraction for all WWTPs. From a fluorescence perspective, the EfOM of the AAO process was rich in humic matter, while the EfOM of the oxidation ditch (OD) process was rich in protein matter. Disinfectants tended to transfer EfOM with high molecular weight (MW) (>6 kDa) to those with low MW (<0.5 kDa). Chlorination, UV + Cl and UV/Cl were more reactive to humic matter, while chloramination and chlorine dioxide were more reactive to protein matter. The formation of known DBPs was mainly dependent on humic matter, while protein matter was more likely to generate unknown DBPs. N-DBPs only accounted for 5.7%–17.7% of the total DBPs, but contributed more than 70% of the calculated toxicity, among which bromochloroacetonitrile (BCAN), dichloroacetonitrile (DCAN), and monobromoacetamide (MBAcAm) were the most important contributors to the calculated cytotoxicity. Monobromoacetic acid (MBAA) and MBAcAm were the primary drivers of the calculated genotoxicity. Overall, UV + Cl was the suggested optimal disinfection method for WWTPs.

Research Progress of Sewage Treatment Technology in Small and Medium Sized Towns

A / O process, oxidation ditch process and other leading technologies used in China's cities, Europe and the United States and other developed countries have been proved to be effective water pollution control technologies. They have their own advantages and disadvantages, and their applicability is also different. However, for small and medium-sized urban sewage treatment plants, these methods may not be suitable. Therefore, for small and medium-sized urban sewage treatment plants, we should consider the problems of technology, management, investment and operation. Therefore, we should look for more convenient, simple operation, low investment and operation cost methods that are more suitable for small towns. In this paper, several common sewage treatment processes are compared to determine the type of sewage treatment process in small and medium-sized towns.

Case Study of a Cost Reduction Trial Based on Postponement of Sludge Withdrawal from an Oxidation Ditch Process with a Small Sludge-Reduction Process

Case Study of a Cost Reduction Trial Based on Postponement of Sludge Withdrawal from an Oxidation Ditch Process with a Small Sludge-Reduction Process

Design of Sewage Treatment Process of Shaowu Second Sewage Treatment Plant Based on the Modified Carrousel Oxidation Ditch

This paper is designed for the sewage treatment process of Shaowu City Second Sewage Treatment Plant, focusing on the modified card oxidation ditch process. This sewage treatment plant is mainly purified by living sewage in Shaowu City, and the processing scale is 10,000 m3d-1. According to the sewage quality and the reality of urban development, this paper selects the hydrolyzate + oxidation ditch + concrete precipitation process. The sewage first hydrolyzedate the acidified tank before entering the secondary treatment to increase the sewage’s sewage, then remove the main organic matter in the water and complete the nitrogen removal phosphorus. Finally, further remove the suspension in water. The material and total phosphorus have enabled water quality to meet the “Sewage Treatment Plant Pollutant Emission Standard” (GB18918-2002). The project is expected to invest 3001,500 yuan, and the wastewater operating cost of the equivalent is 0.57 yuan/ton.

Nitrogen removal characteristics of biofilms in each area of a full-scale AAO oxidation ditch process.

Plastic carriers were installed in different areas of a full-scale anaerobic/anoxic/aerobic (AAO) oxidation ditch process, and the dynamics of nitrogen removal, biofilm morphologies, and microorganism species were investigated. The results showed that the biofilm at the front of the aerobic area (dissolved oxygen [DO]=0.93mgL-1) provided the best denitrification, with specific nitrate and nitrite reduction rates of 10.16 and 3.78mg·(g·h)-1, respectively. The biofilm in the middle of the aerobic area (DO=1.27mgL-1) exhibited the best nitrification performance, with a maximum specific ammonia oxidation rate of 3.21mg·(g·h)-1. The biofilm at the end of the aerobic area (DO=0.01mgL-1) exhibited the highest anammox potential with a maximum specific anammox rate of 0.67mg·(g·h)-1. No correlation was observed between the specific nitrogen removal rates and abundance of nitrogen-removing microorganisms at the genus level. Biofilm denitrification during the process was primarily completed by heterotrophic denitrifying bacteria (Thauera, Acinetobacter, Hyphomicrobium, and Thermomonas). Aerobic denitrifying bacteria (0.19% Thauera and 0.34% Hyphomicrobium) were identified as the main denitrifying bacteria in the middle of the aerobic area. The dominant nitrifying microorganisms in the middle of the aerobic area were Nitrosomonas (0.50%) and Nitrospira (1.04%). A biofilm in the end of the aerobic area exhibited specific anammox potential, which may have been related to the dominance of 0.024% Candidatus Brocadia. Kinetic analysis revealed that adding plastic carriers to the front and middle of the aerobic area contributed to stable nitrogen removal efficiency.

B3 공정의 유가공 폐수 처리 특성 평가

As the milk processing wastewater contains large amount of soluble substances and its quality and quantity changes widely, it is not easy to treat efficiently. In this work, we investigated two biological processes for milk processing wastewater treatment, the oxidation ditch process for S Milk Y plant and the B3 process for S Milk G plant. The comparison was made using the one year operation results of these two full-scale plants focusing on the removal of organic matters and nutrients(N, P). Based on the steady state data of the B3 process, hydraulic retention time (HRT) of 3.2 days and sludge retention time (SRT) of 13.8 days were found to be appropriate for milk processing wastewater. Under these conditions the removal efficiencies of organic matters in terms of BOD, CODMn and SS were 99.7%, 98.4% and 99.5%, respectively. In addition, the removal of T-N and T-P amounted to 91.9% and 96.9%, respectively. Therefore, it was confirmed that organic matter and nutrients in milk processing wastewater can be effectively treated with the B3 process if proper operating conditions are maintained. When compared with the oxidation ditch process, the B3 process showed greater removal efficiencies especially for nitrogen and phosphorus.

Using molecular weight-based fluorescent detector to characterize dissolved effluent organic matter in oxidation ditch with algae.

Implementation of microalgae has been considered for enhancing effluent wastewater quality. However, it can cause environmental issues due to the release of extracellular and algal organic matter in the biological process. This study aimed to investigate the characteristics of dissolved effluent as algae- and bacteria-derived organic matter during the oxidation ditch process. Furthermore, experiments were conducted under three combinations filled by Spirulina platensis, Chlorella vulgaris, and without microalgae. The results showed that dissolved effluent organic matter was more aromatic and hydrophobic than before treatment. Fluorescence spectroscopy identified two components-aromatic protein-like and soluble microbial product-like components-at excitation/emission of 230/345nm and 320/345nm after treatment, instead of fulvic acid-like at 230/420nm and humic acid-like at 320/420nm in raw wastewater. These components were fractionated based on the average of molecular weight cut-offs (MWCOs), and high (MWCOs > 50,000Da), medium (MWCOs 50,000-1650Da), and low molecular weights (MWCOs < 1650Da) were reported. Biological oxidation ditch under symbiosis algal bacteria generated humic and fulvic acid with a higher MWCOs than the process without algal. The quality and quantity of dissolved effluent organic matter in an oxidation ditch reactor were significantly affected by algal-bacteria symbiotic.

The changing pattern of bioaerosol characteristics, source and risk under diversity brush aerator speed

Bioaerosols containing pathogens released from wastewater treatment plants (WWTP) may pose potential health risks to workers on-site and residents downwind. In this study, sampling points were set up in the wastewater treatment facility to investigate the generation pattern of bioaerosols in the aeration tank section. High-throughput sequencing was utilized to assay the intestinal bacteria population, while the health risks associated with airborne bacteria were estimated based on average daily dose rates. The contribution of wastewater to bioaerosols was evaluated using the traceability analysis. As the rotational speed increased from 200 rpm to 800 rpm, the concentration of culturable bacteria increased from 397 CFU/m3 to 1611 CFU/m3, the proportion of bacteria attached to particles with an aerodynamic diameter larger than 4.7 µm increased from 30.41% to 48.44%, and the Shannon index of air samples increased from 1.032485 to 1.282065. Microbial composition, sources, and health risks of bioaerosols also changed as the rotational speed increased. The results showed that the predominant bacteria in the air at 200 rpm were Bacillus (78.78%), Paenibacillus (11.77%) and Lysinibacillus (1.40%). When the rotating speed reached 800 rpm, the dominant bacteria became Bacillus (55.50%), Acinetobacter (31.01%), and Paenarthrobacter (13.17%). The contribution of the wastewater to bioaerosols increased from 46.49% to 65.10%, in which surface water was the main source of bioaerosols (34.64% on average). Although the contribution of bottom water was lower than that of surface water, its contribution increased more, from 15.36% to 29.31%. The health risk of bioaerosols was 1.28 × 10−2 on average, which increased with the increase of rotational speed. At the same exposure concentration, children (2.31 × 10−2) have a higher exposure risk than adults (7.67 × 10−3). This study is aimed at exploring the variation law of bioaerosols discharged from WWTP with oxidation ditch process and providing preliminary data for reducing its risk.

Effects of different treatment processes in four municipal wastewater treatment plants on the transport and fate of microplastics

The behavior of microplastics in wastewater treatment plants has been investigated, but specific effects of treatment process on microplastics' fate are still unclear due to varied analysis methods and regional differences. In this study, four wastewater treatment plants in Ningbo of southeastern China with different treatment processes were selected to investigate transport and fate of microplastics. Based on number of microplastic particles, fibers and fragments were the main microplastics types in wastewater, while synthetic cellulose represented the largest fraction. The dominance of fibers (76.7%–90.0%) and small particle sizes (<2.0 mm, 62.5%–81.5%) in effluents suggested that they escaped easily from the wastewater treatment plants. The abundance of microplastics particles decreased from 78.0 ± 2.9 items/L in influent to 6.0 ± 2.8 items/L in effluent for anaerobic-anoxic-oxic process, 100.0 ± 3.1 items/L to 4.3 ± 3.4 items/L for sequencing batch reactor activated sludge process, 105.0 ± 5.3 items/L to 3.5 ± 2.6 items/L for cyclic activated sludge technology, 65.0 ± 4.3 items/L to 3.0 ± 1.6 items/L for oxidation ditch process. The microplastics removal capacity of primary and secondary treatment processes for four wastewater treatment plants ranged from 83.7% to 96.3%. Application of different tertiary treatment processes (coagulation/flocculation, membrane related technology and disinfection) enhanced microplastics removal to achieve overall removal rate of 92.3%–96.7%. The removed microplastics from the wastewater treatment plants were mainly transferred to sludge (226.1 ± 95.7–896.0 ± 144.0 items/g dry weight). The biological treatment unit played an important role in microplastics removal with rates varying between 86.9%–95.2%, while tertiary treatment reduced daily microplastics emission 1.4 × 108–2.3 × 108 items/day. This study suggests that proper selection of wastewater treatment unit could significantly reduce the emission number of microplastics, which supports an efficient control strategy of microplastics in wastewater treatment plants.

The prevalence and removal of antibiotic resistance genes in full-scale wastewater treatment plants: Bacterial host, influencing factors and correlation with nitrogen metabolic pathway

This study investigated the prevalence of antibiotic resistance genes (ARGs) in the influent, effluent, and waste activated sludge (WAS) of eight full-scale municipal wastewater treatment plants (WWTPs) in Shanghai, China. A comprehensive understanding of the correlation between various influencing factors (characteristics of wastewater and WAS, antibiotics, metals, mobile genetic elements) and ARGs was explored. Among the eight full-scale WWTPs, the Unitank process was inefficient in removing typical ARGs compared with continuous-flow anaerobic-anoxic-aerobic and oxidation ditch processes. Antibiotic was identified as the most influential factor affecting the occurrence of ARGs in wastewater, followed by flow rate and nutrients. Positive correlations were observed between antibiotics and their corresponding ARGs in the influent, while this correlation disappeared in the WAS. Class I integron, wastewater characteristics (nitrogen and flow rate), antibiotics (ofloxacin, sulfamethazine, and erythromycin), metals (Mg, Al, Fe, and Mn) were identified as crucial factors comprehensively affecting the distribution of ARGs in WAS. Dissimilatory nitrate reduction profoundly influenced the fate of ARGs during wastewater treatment processes, and K04561 (norB), K02567 (napA), K00262 (gdhA), K00284 (gltS) were identified as the most significant genes in the nitrogen metabolism pathway (ko00910). This study provides a new perspective for comprehensively understanding the occurrence and dissemination of ARGs in WWTPs.

Aerobic biofilm providing a habitat for anammox bacterial survival in mainstream of municipal wastewater treatment plants

Enrichment and accumulation of anaerobic ammonium oxidation (anammox) bacteria is a key to success in anammox-based nitrogen removal in mainstream in municipal wastewater treatment plants (WWTPs). In this study, relatively high percentage of anammox bacteria was detected in biofilm employed in aerobic zone of two WWTPs (one with Orbal Oxidation ditch process, and the other with anaerobic-anoxic-oxic (A2/O) process) in Xi'an, China. The high-throughput sequencing results showed that Ca. Brocadia responsible for nitrogen removal detected with relative abundance of 0.95 ± 0.21% (Orbal Oxidation ditch) and 0.71 ± 0.14% (A2/O) of the total bacteria in biofilm. The anammox activities could be estimated to be 5.98 ± 1.32 mg NH4+-N/g VSS/d (Orbal oxidation ditch) and 1.36 ± 0.25 mg NH4+-N/g VSS/d (A2/O) after short-term precultivation. The contribution to nitrogen removal by anammox process were 2.49 ± 0.87% (Orbal oxidation ditch) and 2.89 ± 2.06% (A2/O) through mass balance calculation. In addition, enhanced batch test demonstrated that partial-nitritation process might play an important role in anammox enrichment but need further research. Overall, this study suggested that aerobic biofilm (AB) might be a candidate to enhance nitrogen removal in mainstream.

Microplastics in Wastewater and Drinking Water Treatment Plants: Occurrence and Removal of Microfibres

Microplastics (MPs), and specifically microfibres (MPFs), are ubiquitous in water bodies, including wastewater and drinking water. In this work, a thorough literature review on the occurrence and removal of MPs, and specifically MPFs in WWTPs and DWTPs, has been carried out. When the water is treated, an average microfiber removal efficiency over 70% is achieved in WWTPs and DWTPs. These high percentages are still inefficient for avoiding the presence of a large number of microfibres in treated wastewater and also in tap water. RSF, DAF, oxidation ditch and CAS processes have been described as the most efficient treatments for eliminating MPFs from wastewater treatment. It is remarkable the wide range of the data reported on this topic; for example, treated wastewater contains between not detected and 347 MPFs/L, whereas tap water contains between not detected and 168 MPFs/L. Microfibres constitute more than half of the MPs found in treated wastewater and sewage sludge, whereas in DWTP effluents the percentage of MPFs is around 32%. Nevertheless, the relative amount of MPFs reported in tap water is notably higher (71%). Microfibres from WWTPs are discharged to the environment, being a source of MP pollution. Additionally, MPs released by DWTPs directly enter the drinking water lines, which constitute a direct route for MP human consumption, so that it has been estimated that an adult may ingest an average value of 7500 MPFs per year only via tap water. Thus, this review provides an update on the performance of WWTPs and DWTPs in removing MPs from water, which is an issue of great interest.

Application of Flow Field Analysis in the Process Design of Modified Microporous Aeration Oxidation Ditch

According to the environment and water quality factors of the project location, an improved microporous aeration oxidation ditch process is designed, which has the characteristics of biochemical reaction of space division, microporous aeration, infinite water circulation in the ditch, and multiple water inlets; under simplified boundary conditions, based on the CFD method, the SSTK-W model is used to close the RANS equation to simulate the flow field in the hypoxic and aerobic areas. With the optimal equipment configuration and the lowest energy consumption, the flow velocity in the trench is more than 0.3m/s, to ensure high buffering capacity of the process; study the flow field state and the unfavorable flow velocity under the optimized operation state of the flow thruster; the rationality of the design is verified through the commissioning and operation of the sewage treatment plant.

Effect of oxidation ditch and anaerobic-anoxic-oxic processes on CX3R-type disinfection by-product formation during wastewater treatment

The high chlorine dosages in wastewater treatment plants during the COVID-19 pandemic may result in increased formation of disinfection by-products (DBPs), posing great threat to the aquatic ecosystem of the receiving water body and the public health in the downstream area. However, limited information is available on the effect of biological wastewater treatment processes on the formation of CX3R-type DBPs. This study investigated the effect of oxidation ditch (OD) and anaerobic-anoxic-oxic (AAO), two widely used biological wastewater treatment processes, on the formation of five classes of CX3R-type DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetaldehydes (HALs), haloacetonitriles (HANs) and halonitromethanes (HNMs), during chlorination. Experimental results showed that biological treatment effectively reduced the dissolved organic carbon (DOC) and UV254, while it increased the dissolved organic nitrogen (DON), and therefore the ratio of DON/DOC. In addition, increases in the contents of soluble microbial product- and humic acid-like matters, and the transformation of high molecular weight (MW) fractions in the dissolved organic matter into low MW fractions were observed after OD and AAO processes. Although biological treatment effectively decreased the formation of Cl-THMs, Cl-HAAs, Cl-HANs and Cl-HNMs, the formation of DBCM, DBAA, BDCAA, DBCAA, DCAL, TCAL and DBAN (where C = chloro, B = bromo, D = di, T = tri) all increased significantly, due to the increased formation reactivity. Moreover, biological treatment increased the ratio of bromide/DOC and bromine incorporation into THMs, HAAs and DHANs except for HALs and THANs. Different from previous studies, this study revealed that biological treatment increased the formation of some DBPs, especially brominated DBPs, despite the efficient removal of organic matters. It provides insights into the DBP risk control in wastewater treatment, particularly during the COVID-19 pandemic.

Experimental study on aeration efficiency in a pilot‐scale decelerated oxidation ditch equipped with fine bubble diffusers and impellers

AbstractThis work is an experimental study on the oxygen transfer capability and efficiency in a pilot‐scale decelerated oxidation ditch equipped with fine bubble diffusers and impellers (inducing horizontal liquid flows). Aqueous solutions of carboxymethyl cellulose (CMC) exhibiting shear‐thinning rheological properties are selected to simulate activated sludge in the oxidation ditch process. The effect of air flow rate and horizontal liquid velocity along the loop channel on oxygen transfer capability and aeration efficiency is examined in tap water and CMC aqueous solutions. The standard volumetric mass transfer coefficient KLa20, standard oxygen transfer efficiency (SOTE), and standard aeration efficiency (SAE) are introduced to study the oxygen mass transfer performance and energy consumption efficiency in the oxidation ditch. The results show that KLa20, SOTE, and SAE in CMC aqueous solutions follow similar trends observed in tap water. Due to the effect of shear‐thinning rheological properties, KLa20, SOTE, and SAE in CMC aqueous solutions are smaller than those in tap water. Two dimensionless numbers, Froude number and Ohnesorge number are introduced to study the oxygen transfer efficiency through the consideration of the combined influence of aeration, crossflow, gas bubble size, and physical properties of the liquid phase.

Nitrous oxide (N2O) emissions from a pilot-scale oxidation ditch under different COD/N ratios, aeration rates and two shock-load conditions

Nitrous oxide (N2O) generated from wastewater treatment plants (WWTPs) has drawn attention due to its high emission load and significant greenhouse effect. In the present study, N2O emissions from a pilot-scale Carrousel oxidation ditch under various chemical oxygen demand (COD) to nitrogen ratio (COD/N) and aeration rates were systematically investigated. The highest N2O emission factor was 0.142 ± 0.013%, at COD/N of 5 and aeration rate of 1.8 m3 h−1, which was much lower than the majority of previous studies. The results could be attributed to the high internal recycle ratio of the oxidation ditch process which lightened the burden of influent load to the system. The profiles of N2O emissions and dissolved N2O concentration along the channels showed a distinct spatial variation that N2O emissions primarily occurred in the aeration zones due to the air stripping effect. However, both the aeration and anoxic zones contributed to N2O generation due to autotrophic nitrification (AN), which was considered to be the main N2O generation process. In addition, two simulated shock-load conditions, ammonia overload shock and aeration failure shock, were carried out to explore the response of the biological nitrogen removal (BNR) system. The results indicated that both shock-loads lead to excessive N2O emissions, especially at higher aeration rates, which could be explained by the improved N2O generation by AN process during the shock-load period. This study offered new insights into the role of operational parameters to N2O emission and the alternative approach for N2O mitigation during both the steady-state operation and shock-load conditions in the oxidation ditch process.

Determine the most effective process control parameters on activated sludge based on particle swarm optimisation algorithm (Case Study: South wastewater treatment plant of Tehran)

ABSTRACT Wastewater treatment plants (WWTPs) are major energy consumers and cause environmental impact on receiving waters. Many WWTPs are operated in a less-than-optimal manner with respect to both treatment and energy efficiency. A better solution is to optimize the operation and processes of the existing WWTPs.Therefore, the most effective process parameter for providing control strategies was determined.The South WWTP of Tehran was designed and simulated based on the activated sludge model using MATLAB/Simulink software for the first time in the country to obtain the factors affecting WWTP. To calibrate this model some kinetic andstoichiometric coefficients were determined. Then the simulator validation was performed by three error calculation methods. Finally,the values of three main controllers, including the optimum rate or return activated sludge (RAS), internal recycle (IR) and oxygen transfer coefficient (KLa) are determined using the Particle Swarm Optimization algorithm.According to the results, coefficients such as Y, kd, K and KS for Oxidation-Ditch process were in the range of 0.303-0.331mgVSS /mg sCOD, 0.030-0.033 1/day, 1.65-1.93 1/day and 37.6-44.92mg sCOD/l, respectively and the Mean of COD, BOD5, TSS and TN removal was obtained 94.8 ± 0.4, 97.3 ± 0.65, 94.7 ± 1.5 and 56 ± 7.46, respectively. Also, the percentage of Root Mean Square forTN, TSS, COD, BOD5 was 3.14%, 2.95%, 3.13% and 5.2%, respectively, Pearson correlation coefficient was 0.88, 0.93, 0.89, 0.99 and absolute mean error of 2.62%, 2.47%, 2.6% and 3.58%,respectively, which shows that the simulation outputs are compatible with the effluent of plant. To achieve the best process performance conditions, RAS and IR must be considered for1.7 and 0.8 percent of influent wastewater and KLa is suggested to be 154 d-1.Therefore, by using the optimization performed, the effect of other controllers on the process can be investigated and selected.

Microalgae Oil Production Using Wastewater in Japan—Introducing Operational Cost Function for Sustainable Management of WWTP

A comparative evaluation of economic efficiency was performed for native polyculture microalgae oil production in an oxidation ditch (OD) process wastewater treatment plant (WWTP). A cost function was developed for the process. The operational cost per 1 m3 of wastewater (w.w.) was 1.34 $/m3-w.w. in the existing scenario, 1.29 $/m3-w.w. in algal scenario A (no cost for CO2 and waste heat) and 1.36 $/m3-w.w. in algal scenario B (no cost for CO2). The conditions were set as follows: hydraulic retention time (HRT): 4 days, microalgal productivity: 0.148 g/L and daily treatment volume: 81.6 m3-w.w./d. The cost differences were related to the increase in polymer flocculants for algae separation (+0.23 $/m3-w.w), carbon credits from CO2 absorption (−0.01 $/m3-w.w), the sales of biocrude (−0.04 $/m3-w.w) and sludge disposal (−0.18 $/m3-w.w). Hence, the introduction of the algae scenario was the same cost-effective as the existing scenario. Microalgae oil production in an OD process WWTP can serve as a new energy system and reduce the environmental load in a society with a declining population.