Full-scale Sewage Treatment Plants Research Articles

Modeling of novel processes for eliminating sidestreams impacts on full-scale sewage treatment plant using GPS-X7

The novel process consisted of two steps was established by combining all sidestreams lines (supernatant gravity thickener, underflow mechanical thickener, and centrate), treating them together away from the mainstream treatment plant, and returning treated sidestreams effluents to the plant outfall instead of plant head. The two steps novelty treatment combined degradation, nitrification, and dilution processes. To treat combined sidestreams, a novel pilot extended nutrient moving bed biofilm reactor was developed. The effects of sidestream elimination on a full-scale anaerobic/anoxic/oxic system were simulated using GPS-X7. The statistical results of R values greater than 0.8 and NMSE values near zero proved the calibrated model’s validation. The novel system successfully removed 98, 93, 100, 85, 98, 100, and 98% of BOD, COD, NH4, NO3, TSS, H2S, and PO4-P from sidestreams, respectively. Furthermore, the simulation results showed that eliminating sidestreams has reduced volumes of full-scale A2/O facilities, controlled hydraulic and pollutants shocks, and minimized cost and energy. The novel process proved successful in treating combined sidestreams and eliminating their impacts on the A/O2 system.

Technical Note 6 - Applicability aerobic granular sludge technology in the Brazilian context

Aerobic granular sludge (AGS) is currently considered one of the most promising technologies for biological wastewater treatment. This fact is mainly due to the combined removal of organic matter and nutrients in the same reactor, eliminating secondary settlers, making it one of the most compact technology on the market. However, there are several reports of problems, including: (i) instability of the granular biomass; (ii) long start-up periods due to slow granule formation, especially when using sewage with a low concentration of organic matter; (iii) accumulation of nitrite in the final effluent; (iv) high demand for automation; and (v) operational process not yet fully established. Thus, despite considerable advances in sewage treatment with AGS systems and the increase in the number of full-scale sewage treatment plants (STPs) in several countries around the world, an integrated assessment of its application in Brazil is necessary. This technical note aims to present the state-of-the-art of AGS system, as well as to bring up a more in-depth discussion, in the Brazilian context, on the need or not to adopt it, and in what situations it should be implemented to replace other sewage treatment technologies with greater mastery of national engineering and usual lower investment and operating costs.

Performance and Sustainability Assessment of Full-Scale Sewage Treatment Plants in Northern India Using Multiple-Criteria Decision-Making Methods

In this study, an intensive performance assessment of 36 sewage treatment plants (STPs) is carried out. The STPs were based on the process technologies: moving-bed bioreactor (MBBR), sequencing batch reactor (SBR), waste stabilization pond (WSP), and upflow anaerobic sludge blanket reactor (UASB) with posttreatment technologies of extended aeration (EA), surface aeration, and polishing ponds, with treatment capacities of 3 to 40 million L per day. The pollutant removal performance of the STPs was ranked using the gray relational analysis method, which revealed that the SBR systems ranked higher, followed by UASB with EA, whereas MBBRs, UASB with other posttreatment options, and WSP performed satisfactorily to poor. Further, the preference ranking organization method for enrichment evaluation (PROMETHEE) multiple-criteria decision-making (MCDM) approach using the fuzzy analytic hierarchy process followed by preference ranking organization method for enrichment evaluation method evaluated the major wastewater treatment technologies using three sustainability criteria: environmental, economic, and technical aspects. The MCDM method evaluation revealed that the UASB + EA method, with its lower greenhouse gas emissions, energy requirement, sludge generation, and energy and resource recovery characteristics, outranked other treatment technologies, followed by SBR. The MCDM results were later confirmed using geometrical analysis for the interactive aid method. Hence, this study summarizes that the anaerobic process followed by microaerobic technologies still possesses the capability to achieve stringent disposal standards almost equivalent to intensive aerobic technologies.

Anaerobic digestion of sewage sludge has no effect on glucocorticoid and anti-progestagenic activity but increases estrogenicity three-fold

Although the recovery and beneficial reuse of organic matter and nutrients from sludge represents an important move towards environmental sustainability, the accumulation of chemicals in biosolid-amended soils could pose serious environmental and human health risks. However, (eco)toxicological profiling of complex chemical mixtures in biosolids is currently limited. In particular, the effect of anaerobic digestion (AD), the most common stabilization process for sewage sludge, on the (eco)toxicity of those complex mixtures is poorly studied. In this work, we fill this research gap by applying an effect-based monitoring approach to screen sludge samples (n = 4) from a full-scale sewage treatment plant before and after conventional mesophilic (37 °C) AD using a battery of cell-based in vitro bioassays for four types of hormonal activity: estrogenic, androgenic, progestagenic and glucocorticoid activity, both in agonist and antagonist modes. We detected estrogenic, glucocorticoid and anti-progestagenic activity in all sludge samples. The glucocorticoid and anti-progestagenic activity remained mostly unchanged after AD treatment, but estrogenicity increased three-fold, likely as a result of bioactivation processes in the digestor. This study presents the first report on the concentration and fate of glucocorticoid and anti-progestagenic activity in AD. Future research should apply bioanalytical tools to a wider range of sludge samples to get a better understanding of the typical hormonal activity in sludge and develop effect-based trigger (EBT) values for biosolids to help interpret the risk posed by the hormonal activity detected in sludge.

Model-Based Solution for Upgrading Nitrogen Removal for a Full-Scale Municipal Wastewater Treatment Plant with CASS Process

Aiming at providing cost-effective approach for upgrading the existing municipal wastewater treatment plants in the cold region of China to meet more stringent discharge standards of nitrogen removal, a full-scale sewage treatment plant with the CASS process was selected through focusing on biological process, key equipment and hydrodynamics in bioreactors by the activated sludge model 1 (ASM1) and computational fluid dynamics (CFD) model. Influent COD fractions and the key characteristic parameters (YH and bH) of the activated sludge were determined through the respirometry at temperatures of 10 °C and 20 °C, respectively. The layout of submerged agitator installation in the bioreactor of the CASS process was optimized through CFD simulation. The calculation of the average relative deviation (less than 20%) between simulated data and the operation data, demonstrated that the ASM1 model could be reasonably used in the wastewater treatment plant simulation. The upgrade solution based on modelling of ASM1 and CFD was successfully applied in practice, which not only made the effluent COD, NH4+-N and TN concentrations meet with the discharge standard of Grade I-A, but also reduced the energy consumption by 25% and 16.67% in summer and winter, respectively. After upgrading, microbial diversity increased in both summer and winter, with an especially significant increase of the relative abundance of denitrifying bacteria.

Simultaneous occurrence and analysis of both anammox and n-damo bacteria in five full-scale wastewater treatment plants

Anaerobic ammonium oxidation (anammox) and nitrite-dependent anaerobic methane oxidation (n-damo) processes are two newly discovered biochemical pathways for removal of reactive nitrogen species and methane. An investigation was initiated to investigate the simultaneous removal of ammonium and methane and the corresponding microorganisms in a full-scale sewage treatment plant and four landfill leachate treatment plants. In this study, hzsB and pmoA genes were used to amplify the genomic DNA of these samples to reveal the diversity of anammox bacteria and n-damo bacteria in these WWTPs. Both anammox bacteria and n-damo bacteria were detected successfully in all samples. The hzsB gene-based PCR amplified sequences featured three genera of Candidatus (Ca.) Brocadia, Ca. Kuenenia and Ca. Jettenia in these WWTPs, while the pmoA gene amplification showed two species of Ca. Methylomirabilis oxyfera and Ca. Methylomirabilis sinica. It was observed that after inoculation of anammox sludge, Brocadia becomes more dominant from the initial co-existing consortium of Kuenenia and Brocadia, and the community diversity decreased accordingly. Based on quantitative 16S rRNA gene PCR, the abundance of anammox bacteria ranged from 2.64 × 106 to 1.73 × 1013 copies per gram dry sludge in the five plants, particularly high on the carriers of landfill leachate wastewaters and the abundance of n-damo bacteria ranged from 2.52 × 107 to 2.19 × 108 copies per gram dry sludge in the five plants. Results shows that abundances of anammox bacteria and AOB (ammonium oxidizing bacteria) were limited by the lower ammonium in the sewage treatment plant, but were higher corresponding to ammonium concentration. Successful inoculation of anammox bacteria was achieved in practical engineering systems and the co-occurrence of anammox bacteria and n-damo bacteria plays an important role in N and C removal in WWTPs.

Study of the performance of disinfection with sodium hypochlorite on a full-scale sewage treatment plant

A full-scale sewage treatment plant was investigated to assess the performance of the disinfection stage. Sodium hypochlorite was used as a disinfectant agent and the process efficiency was evaluated by E.coli removal. The research took place over a period of two years in order to evaluate the effect of retention time (t) and residual chlorine (Cr) under different seasonal conditions. The effectiveness of E.coli removal with sodium hypochlorite proved to be strictly dependent on the factor CR t (product of residual chlorine with the contact time). The regression line of the experimental points was, on the whole, well comparable with the model proposed by Collins, especially in the field of CRt lower than 30 mg L-1 min.

하수처리장에서 탈수여액의 총부하량 저감에 관한 연구

하수처리장에서 탈수여액의 총부하량 저감에 관한 연구

Microbial diversity reveals the partial denitrification-anammox process serves as a new pathway in the first mainstream anammox plant

A full-scale sewage treatment plant in Xi'an city is discovered as the first mainstream anaerobic ammonia oxidation (anammox) treatment process in China. Whether its biological mechanism is the nitritation-anammox or partial denitrification (PD)-anammox brought violent controversy between two groups. As a third party, here we uncovered the mystery of the moving-bed biofilm reactor (MBBR) as a PD-anammox process by analyzing the diversity and phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt) of microbes in anoxic pond. Anammox bacteria was found in the MBBR anoxic tank, which abundance is 8.9 times of that in the common anaerobic-anoxic-oxic process, confirming the existence of anammox process. The denitrifying bacteria (DNB) content in the anoxic tank is 5.9 times of the content of ammonia oxidizing bacteria (AOB), thus the DNB-anammox system is proved at the microbial composition level. The PICRUSt analysis found that ammonium nitrogen is mainly derived from the deamination of urea. The functional genes NAR and AMO of DNB and AOB are 910.84 and 5.80 rpms, respectively. The NAR gene content is 157.0 times of the AMO gene content and it is proved at the genetic level that the nitrite in the anoxic pool is mainly derived from denitrification. This study demonstrated the feasibility and advantages of the PD-anammox in the anammox process, which is different from the traditional nitritation-anammox demonstrated in Strass Wastewater Treatment Plant, Austria and Changi Water Reclamation Plant, Singapore and provided an alternative option for the mainstream application of anammox.

Emerging contaminants in aquatic environments and coastal waters affected by urban wastewater discharge in Thailand: An ecological risk perspective

Emerging contaminants such as synthetic musks and UV-filters as ingredients personal care products were widely used in human daily life in Thailand. The occurrence and fate of four synthetic musks and nine UV-filters were investigated in eight full-scale sewage treatment plants (STPs) and their receiving aquatic environments in Bangkok and Pattaya, Thailand. All target compounds were detected in every single sample from STPs and surface water with magnitude from ng/L to μg/L. HHCB-lactone and HMS were found as the predominant musk and UV filter in influent and effluent of STPs, respectively. HHCB-lactone was also found with the highest concentration up to 79501 ng/g (dw) in the sludge. Low removal efficiency range from −37% (HHCB-lactone) to 58% (AHTN) were found for four musks in the STPs. The total emission of Σ4musks and Σ9UV-filters were estimated to be up to 16.7 mg/person/day and 0.28 mg/person/day by the STPs. Three synthetic musks and seven UV-filters were detected in fish from the receiving river. Concentration and emission of musks and UV filters found in this study from Thailand were much higher than those reported in many other countries worldwide. The preliminary ecological risk assessment showed that Musk xylene, 4-MBC and OC may pose high risk to aquatic organisms in the riverine and estuarine environment in Thailand.

Modeling of a full-scale sewage treatment plant to predict the nutrient removal efficiency using a long short-term memory (LSTM) neural network

A long short-term memory (LSTM)-based neural network was proposed and developed to predict the ammonium (NH4-N), total nitrogen (TN), and total phosphorus (TP) removal efficiency of an anaerobic-anoxic-oxic membrane bioreactor (A-A-O MBR) system after data visualization using Python programming. The influent wastewater characteristics, including, total organic contents, NH4-N, TN, TP, chemical oxygen demand, suspended solids, and operating parameters, such as dissolved oxygen, oxidation-reduction potential, and mixed-liquor suspended solids, were considered as inputs, while removal efficiency was taken as an output parameter. First, data analysis and its normalization were conducted to improve the learning speed of the model. Performance criteria of the proposed model were evaluated based on statistical values, including the mean-square error (MSE) and root-mean-square error-observations standard deviation ratio (RSR). Based on the goodness-of-fit values, the proposed LSTM model achieved good performance in the testing dataset; calculation results deviated little, indicated by the MSE values of 0.0047, 0.015, and 0.018 for NH4-N, TN, and TP, and RSR values of 0.0104, 0.129, and 0.141, respectively. The proposed LSTM model predicted the most precise removal efficiency for NH4-N of A-A-O MBR system, while TN and TP predictions were comparatively less accurate, but still acceptable. The proposed LSTM model is promising for predicting the nutrient removal efficiency of the A-A-O MBR system in real-time and can aid in establishing process control strategies. Therefore, the proposed LSTM model is an adequate interpolation tool to predict the nutrient removal efficiency of the A-A-O MBR process in wastewater treatment systems.

Removal and recovery of nutrients from municipal sewage: Algal vs. conventional approaches

This paper presents a pilot scale study of an algal-based sewage treatment and resource recovery (STaRR) system capable of treating municipal sewage and recovering its nitrogen- and phosphorous-content as fertilizer. Core components of the STaRR system include i) mixotrophic cultivation of algal biomass in settled sewage; ii) hydrothermal liquefaction (HTL) of the resulting algal biomass, and iii) processing of the products of HTL to recover energy in the form of biocrude and nutrients in the form of struvite. Performance of a pilot-scale STaRR system in recovering nitrogen (N) and phosphorus (P) from settled sewage as struvite is documented and compared with that of existing and emerging technologies. Nutrient removal per unit energy input in the STaRR system is estimated as 257.1 g N/kWh and 36.6 g P/kWh while that in eight full-scale sewage treatment plants (STPs) averaged 74.3 g N/kWh and 135.1 g P/kWh. Energy required to treat primary effluent in the STaRR system (531.5 kWh/MG) is estimated to be lower than the average in the 8 STPs (1,037.9 ± 503.3 kWh/MG). While existing technologies had been originally designed for removal of nutrients rather than any recovery, a review of the literature revealed 12 emerging technologies for nutrient recovery. Nutrient recovery performance of the STaRR system (5.9% N and 71.6% P) is shown to be superior to that of those 12 emerging technologies. Recoveries recorded in the STaRR system translate to a yield of 2.4 kg struvite per 100 m3 of primary effluent. Results of this study imply that the STaRR system deserves due consideration as a greener and sustainable pathway for nutrient removal and recovery from sewage.

Energy potential of biogas and sludge from UASB reactors in the State of Paraná, Brazil

Upflow Anaerobic Sludge Blanket (UASB) reactors are widely used for domestic sewage treatment in Brazil, and generate sludge and biogas as by-products. Typically, the sludge is sent to sanitary landfills, and the biogas is burned in flares. This study assessed the energy potential of these by-products in sewage treatment plants (STPs) located in the state of Paraná, Brazil. First, an overview of biogas energy recovery potential in a full-scale STP based on UASB reactors was carried out. Afterwards, a total of 239 STPs in the state of Paraná were assessed, and the energy potential of the by-products was estimated by a mathematical model. Data were spatially classified using ArcGIS®, taking into account the different effluent characteristics (worst, typical and best scenario), sludge dehydration systems (drying bed and centrifuge) and sizes (small, medium and large). Among the states in Brazil, Paraná presented the highest biogas potential, although nowadays it exploits only 0.4% of its capacity. Biogas was the main by-product generated by UASB reactors in Paraná, and if used in the entire state, it could supply the energy demands of a city with 111,000 inhabitants. Biogas corresponded to 65, 64 and 74% of the total potential (sludge and biogas) for small, medium and large STPs, respectively. The study of the energy potential of the by-products associated with GIS tools positively contributes to the decision-making process in sanitation management and to improve energy sustainability.

Biodegradability assessment of food additives using OECD 301F respirometric test.

The ready biodegradability of twenty food additives, belonging to the classes of artificial sweeteners, natural sweeteners, preservatives and colorings, was investigated using activated sludge as inoculum and OECD 301F respirometric test. According to the results, saccharin, aspartame, sodium cyclamate, xylitol, erythritol, maltitol, potassium sorbate, benzoic acid and sodium ascorbate are characterized as readily biodegradable compounds, partial biodegradation (<60% during the test) was noticed for steviol, inulin, alitame, curcumin, ponceau 4R and tartrazine, while no biodegradation was observed for the other five compounds. The duration of lag phase before the start of biodegradation varied between the target compounds, while their ultimate biodegradation half-life values ranged between 0.7 ± 0.1 days (benzoic acid) and 24.6 ± 1.0 days (curcumin). The expected removal of target compounds due to ultimate biodegradation mechanism was estimated for a biological wastewater treatment system operated at a retention time of one day and percentages higher than 40% were calculated for sodium cyclamate, potassium sorbate and benzoic acid. Higher removal percentages are expected in full-scale Sewage Treatment Plants (STPs) due to the contribution of other mechanisms such as sorption to suspended solids, (bio)transformation and co-metabolic phenomena. Further biodegradation experiments should be conducted under different experimental conditions for the food additives that did not fulfill the requirements of the applied protocol. Future studies should also focus on the occurrence and fate of food colorants and natural sweeteners in full-scale STPs.

Constraints, performance and perspectives of anaerobic sewage treatment: lessons from full-scale sewage treatment plants in Brazil.

There are hundreds of full-scale upflow anaerobic sludge blanket (UASB) reactors in operation in various parts of the tropical world, notably in India and Latin America, Brazil being the holder of the largest park of anaerobic reactors for sewage treatment in the world. Despite the recognized advantages of UASB reactors, there are problems that have prevented their maximum operational performance. Neglecting the existence and delaying the solution of these challenges can jeopardize the important advances made to date, impacting the future of anaerobic technology in Brazil and in other countries. This work aims to evaluate the operational performance of five full-scale UASB reactors in Brazil, taking into account a monitoring period ranging between two and six years. The main observed design, construction, and operational constraints are discussed. Some outlooks for important upcoming developments are also provided, considering that most of the observed drawbacks can be tackled without significant increases on reactor costs.

Experimental study on accumulation of heavy metals in vegetables irrigated with treated wastewater

Treated sewage and industrial effluents are used for irrigation of crops in developing countries which may contain heavy metals in high concentration. It can contaminate soil and accumulate in vegetables. In the present study, the vegetables were irrigated with treated wastewater brought from a nearby full-scale sewage treatment plant. The concentration levels of the Cd, Co, Cu, Mn and Zn in the leaves were found below toxic limits as prescribed in the literature. Daily intake metals values suggest that the consumption of plants grown in treated wastewater and tap water is nearly free of risks, as the dietary daily intake limits of Cu, Fe, Zn, and Mn in adults can range from 1.2 to 3 mg, 10 to 50 mg, 5 to 22 mg and 2 to 20 mg, respectively. The enrichment factor for the treated wastewater irrigated soil was found to decrease in order of Zn > Ni > Pb > Cr > Cu > Co > Mn > Cd.

Salinity-driven heterogeneity toward anammox distribution and growth kinetics.

Anaerobic ammonium oxidation (anammox) has been widely applied for biological nitrogen removal in freshwater systems, and there is a potential for its extension in saline water systems. In this study, the abundance and biodiversity of anammox bacteria were investigated in both saline and freshwater full-scale sewage treatment plants (STPs). The anammox bacteria were widely found in four tested STPs with abundance of 105-107 copies per mL of 16S rRNA gene. Phylogenetic results showed that Ca. Scalindua and Ca. Brocadia dominated in saline and freshwater STPs, respectively. Ca. Kuenenia dominated in one of freshwater STPs. However, redundancy discriminate analysis (RDA) indicates the distribution of Ca. Kuenenia in both saline and freshwater conditions. To further elucidate these observations, the Monod model was integrated with Gauss equation for the evaluation of salinity-induced kinetics. Model results reveal that when nitrite concentration (SNO2-) is higher than nitrite affinity constant (KNO2-), salinity (over ~ 3.0%) is responsible for Candidatus Scalindua dominance over Candidatus Kuenenia. Conversely, in nitrite-depleted conditions (KNO2- ≥ SNO2-), high nitrite affinity leads to the predominance of Ca. Scalindua in all salinities. This study provides fundamental insights into saline anammox applications.

Occurrence and risk assessment of NP, BPA and TCS in sewage treatment plants

A long-term investigation, which covered 6 sampling campaigns over one year, was carried out to evaluate the occurrence, removal and risk of nonylphenol (NP), bisphenol A (BPA) and triclosan (TCS) in two full-scale sewage treatment plants (STPs) in Guangdong, South China. The target compounds were detected in every sample. The influent concentrations of NP were in the ppb level, while TCS in the ppt level. The seasonal variation in the influent was observed due to human consumption and the rainfall. Domestic sewage discharge was an important source of TCS to the STPs. Three kinds of endocrine disrupting compounds (EDCs) could not be completely removed in the STPs, and the activated sludge treatment process contributed to most of the removal of compounds. In addition, the oxic tank and the anaerobic tank both showed good removal performances for target EDCs. According to the results produced from the calculation of the risk quotient, in the STP1 effluents TCS could pose a high risk to the aquatic environment, and STP2 effluents existed high risk of estrogen activity.

Temporal dynamics of activated sludge bacterial communities in two diversity variant full-scale sewage treatment plants.

Bacterial community in activated sludge (AS) is diverse and highly dynamic. Little is known about the mechanism shaping bacterial community composition and dynamics of AS and no study had quantitatively compared the contribution of abiotic environmental factors and biotic associations to the temporal dynamics of AS microbial communities with significantly different diversity. In this study, two full-scale sewage treatment plants (STPs) with distinct operational parameters and influent composition were sampled biweekly over 1year to reveal the correlating factors to whole and sub-groups of AS bacterial community diversity and dynamics. The results show that the bacterial communities of the two STPs were entirely different and correlated with the influent composition and operating configurations. Bacterial associations represented by cohesion metrics and the environmental factor temperature were the primary correlated factors to the temporal bacterial community dynamics within each STP. The STP with high diversity and evenness could treat influent with higher suspended solid and a shorter sludge retention time, and was less correlated with environmental factors, implying the importance of diversity for AS system.

Free-living bacteria and potential bacterial pathogens in sewage treatment plants.

To comprehensively understand the profile of free-living bacteria and potential bacterial pathogens in sewage treatment plants (STPs), this study applied high-throughput sequencing-based metagenomics approaches to investigate the effects of activated sludge (AS) treatment process and ultraviolet (UV) disinfection on the community of bacterial pathogens in two full-scale STPs. A total of 23 bacterial genera were identified as free-living bacteria, and 243 species/OTU97% were identified as potential bacterial pathogens, 6 of which were confidently detected in the STPs (with the total abundances ranging from 0.02 to 14.19%). Both diversity and relative abundance of the detected bacterial pathogens decreased obviously after AS treatment process (p < 0.05), and increased slightly after sedimentation (p < 0.05). UV disinfection shows no obvious effects on the total relative abundance of the free-living pathogenic bacteria in sewage. Although large amounts of the particle-bound pathogens were eliminated through the sewage treatment process, the STPs could not effectively remove the free-living bacterial pathogens, and some pathogenic bacteria (e.g., Pseudomonas aeruginosa) present in the effluent had higher relative abundance after UV disinfection. Overall, the results extend our knowledge regarding the community of potential pathogens (especially free-living pathogens) in STPs.