Rural Wastewater Treatment Plants Research Articles

Performance of full-scale rural wastewater treatment plants in the reduction of antibiotic-resistant bacteria and antibiotic resistance genes from small-city effluents

The main objective of this study was to evaluate the performance of full-scale rural wastewater treatment plants (WWTPs) in the reduction of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) from small-city effluents. Twenty full-scale WWTPs in rural Chile with different biological treatment technologies (vermifiltration (VF), activated sludge (AS) and biodisc (BD)) and disinfection treatments (chlorination (Cl) and UV irradiation (UV)) were monitored and studied in two campaigns: Campaign 1 (20 WWTPs) and Campaign 2 (6 WWTPs). In both campaigns, the rural WWTPs improved the water quality of the effluents very significantly (90%, 70%, and 40% reductions in TU, COD, and NH4+-N, respectively) and reduced ARB and ARG loads by 2–4 log units. All three biological treatments contributed to the final quality of the effluents, especially in terms of microbiological parameters, with statistically indistinguishable efficiencies between them. These results show the importance of rural WWTPs in improving the water quality of urban effluents while reducing microbiological risk and the spread of antibiotic resistance into the environment. The study demonstrates the utility of a non-centralized, self-managed wastewater treatment scheme that can be implemented in many sparsely populated areas around the world.

Surveillance of COVID-19 and influenza A(H1N1) prevalence in China via medicine-based wastewater biomarkers

The simultaneous monitoring of individual or multiple diseases can be achieved by selecting therapeutic medicines used to treat the primary symptoms of the condition as biomarkers in wastewater. This study proposes a novel approach to monitor the prevalence of COVID-19 and influenza A (H1N1) by selecting nine medicines to serve as biomarkers, including three antipyretics, three antivirals, and three cough suppressants. To verify our approach, wastewater samples were collected from seventeen urban and five rural wastewater treatment plants (WWTPs) in a Chinese city over a period of one year. The use of antipyretics increased notably during the COVID-19 pandemic, while the consumption of antivirals for influenza A (H1N1) rose in the post-COVID-19 pandemic period, indicating a minor spike in the occurrence of influenza A (H1N1) after the COVID-19 pandemic. Fever is a significant symptom of COVID-19 and can serve as a reliable indicator of disease prevalence. Our research found that the prevalence of COVID-19 in urban areas was significantly higher (at 78.5 %, 95 % CI: 73.4 % - 83.9 %) than in rural areas (with a prevalence of 48.1 %, 95 % CI: 42.4 % - 53.8 %). The prevalence of COVID-19 in urban areas in this study was consistent with the data reported by the Chinese center for Disease Control and Prevention (82.4 %). Continuous monitoring of WWTPs in urban areas with fluctuating populations and complex demographics can provide early disease warning. Our results demonstrate the feasibility of evaluating community disease prevalence by selecting major therapeutic medicines as biomarkers in wastewater.

Seasonal behavior of pharmaceuticals and personal care products within Chilean rural WWTPs under COVID-19 pandemic conditions

During the COVID-19 pandemic, the consumption of pharmaceuticals and personal care products (PPCPs) increased exponentially. There is an associated risk concerning the presence of PPCPs from wastewater, mainly in rural zones of emerging countries, where sanitation tends to be poor or inefficient. Therefore, this study aimed to evaluate the seasonal behavior of PPCPs within Chilean rural wastewater treatment plants (WWTPs) under COVID-19 pandemic conditions. Ten Chilean rural WWTPs were monitored during 2021, both in the cold (May–September) and warm (November – December) months, being collected semi-composite samples (influent/effluent). WWTPs were based on activated sludge, aerobic lagoons, rotatory discs, activated sludge + bio discs, constructed wetlands, and vermifilter. Physicochemical parameters and PPCPs (azithromycin, ciprofloxacin, caffeine, ibuprofen, losartan, and triclosan) compounds were monitored. Results showed that PPCPs, such as antibiotics (azithromycin, ciprofloxacin: 14.7 – 100%), stimulants (caffeine: 41.5 – 100%), NSAIDs (ibuprofen: 32.9–100%), β-blockers (losartan: 43.5–100%), and disinfectants (triclosan: 45.9–100%) were variably removed. Non-significant differences (p > 0.05) of the PPPCs (effluent concentrations/efficiencies) were reported regarding seasonality and treatment typologies. Moreover, azithromycin, ciprofloxacin and triclosan reported positive correlations (Ɵ ≈ 0 °) with solids. Finally, this study evidenced that COVID-19 pandemic conditioned seasonally variability of PPCPs from wastewater.

Norovirus, Hepatitis A and SARS-CoV-2 surveillance within Chilean rural wastewater treatment plants based on different biological treatment typologies

During the COVID-19 pandemic, wastewater from WWTPs became an interesting source of epidemiological surveillance. However, there is uncertainty about the influence of treatment type on virus removal. The aim of this study was to assess viral surveillance within wastewater treatment plants (WWTPs) based on different biological treatments. Seasonal monitoring (autumn-winter and spring-summer) was conducted in 10 Chilean rural WWTPs, which were based on activated sludge, aerated lagoons, bio-discs, constructed wetlands, vermifilters and mixed systems. Viruses were measured (influent/effluent) by the RT-qPCR technique, using a commercial kit for SARS-CoV-2, NoV GI, NoV GII, and HAV. The detection of SARS-CoV-2 viral variants by genotyping was performed using SARS-CoV-2 Mutation Assays (ThermoFisher Scientific, USA). JC polyomavirus detection (control), as well as a qPCR technique. Results showed that SARS-CoV-2, NoV GI and GII were detected in influents at values between <5 and 462, 0 to 28, and 0 to 75 GC/mL, respectively. HAV was not detected among the studied WWTPs. The monitored WWTPs removed these viruses at percentages between 0 and 100 %. WWTPs based on activated sludge with bio-discs demonstrated to be the most efficient at removing SARS-CoV-2 (up to 98 %) and NoV GI and GII (100 %). Meanwhile, bio-discs technologies were the least efficient for viral removal, due to biofilm detachment, which could also adsorb viral aggregates. A correlation analysis established that solids, pH, and temperature are the most influential parameters in viral removal. Wastewater-based surveillance at WWTP allowed for the detection of Omicron before the Chilean health authorities notified its presence in the population. In addition, surveillance of viruses and other microorganisms could help assess the potential public health risk of wastewater recycling.

High diversity of the emerging pathogen Acinetobacter baumannii and other Acinetobacter spp. in raw manure, biogas plants digestates, and rural and urban wastewater treatment plants with system specific antimicrobial resistance profiles

Carbapenem-resistant Acinetobacter baumannii causing immense treatment problems in hospitals. There is still a knowledge gap on the abundance and stability of acquired resistances and the diversity of resistant Acinetobacter in the environment. The aim of the study was to investigate the diversity and antimicrobial resistances of Acinetobacter spp. released from livestock and human wastewater into the environment. Raw and digested manure of small scale on farm biogas plants as well as untreated and treated wastewater and sewage sludge of rural and urban wastewater treatment plants (WWTPs) were studied comparatively. A total of 132 Acinetobacter isolates were phylogenetically identified (16S rRNA gene and rpoB sequence analyses) and 14 different phylotypes were detected. Fiftytwo isolates represented A. baumannii which were cultured from raw and digested manure of different biogas plants, and most stages of the rural WWTP (no hospital wastewater receiving) and the two studied urban WWTPs receiving veterinarian and human hospital wastewater. Multi-locus sequence typing (Pasteur_MLST) identified 23 novel and 12 known STs of A. baumannii. Most novel STs (18/23) were cultured from livestock samples and the rural WWTP. A. baumannii isolates from livestock and the rural WWTP were susceptible to carbapenems, colistin, ciprofloxacin, ceftazidime, and piperacillin. In contrast, A. baumannii isolates from the two urban WWTPs showed clinical linkage with respect to MLST and were multi-drug resistant (MDR). The presence of viable A. baumannii in digested manure and sewage sludge confirmed the survival of the strict aerobic bacteria during anoxic conditions. The study indicated the spread of diverse Acinetobacter from anthropogenic sources into the environment with a strong linkage of clinial associated MDR A. baumannii strains to the inflow of hospital wastewater to WWTPs. A more frequent detection of Acinetobacter in sewage sludge than effluent waters indicated that particle-attachment of Acinetobacter must be considered by the risk assessment of these bacteria.

Characteristics of rural sewage discharge and a case study on optimal operation of rural sewage treatment plant in Shaanxi, China

Rural wastewater treatment has become an important issue in China. This study investigated 76 rural wastewater treatment plants (WWTPs) in Shaanxi over a one-year period. We found that although rural sewage is suitable for biological treatment (BOD5/COD = 0.38–0.41), it has an obvious intermittent flow cutoff (5–19 h/d) characteristic, resulting in low sewage loading and poor pollutant removal in rural WWTPs. In order to improve operation efficiency and increase economic benefits of the existing rural WWTPs, a pilot-scale A2/O bioreactor was established, and the effect of rural sewage discontinuity (cutoff duration 10 h/d) on A2/O process was studied. An intermittent aeration and dissolved oxygen (DO) regulation operation strategy was developed. The results demonstrated that ammonia oxidizing bacteria (AOB), nitrite oxidizing bacteria (NOB), and polyphosphate accumulating bacteria (PAOs) were all enriched when Taeration:Tstop = 5 h:5h and DO = 2.0–3.0 mg/L. During the subsequent process of reducing DO concentration to 0.5–1.0 mg/L, AOBs (2.43 %) and PAOs (1.91 %) were enriched and NOBs (1.61 %) were panned. The transformation of functional bacteria in the system stimulated partial nitrification and denitrification phosphorus removal (DPR) (nitrite accumulation rate = 46.56 ± 6.88 %, DPR rate = 43.15 ± 3.54 %), which improved the nutrient removal rates. Finally, the optimal operation strategy was applied to a typical town-level WWTP in Ankang, China. The removal rates of NH4+-N, TN, and TP increased from 85.85 ± 1.31 %, 59.77 ± 2.86 %, and 23.91 ± 1.77 % to 94.17 ± 2.02 %, 65.32 ± 4.75 % and 61.05 ± 2.34 %, respectively, and the operating cost was reduced by 118,600 CNY (17,541 USD) per year.

Microbial community origin and fate through a rural wastewater treatment plant.

Conventional wastewater treatment relies on a complex microbiota; however, much of this community is still to be characterized. To better understand the origin, dynamics and fate of bacteria within a wastewater treatment plant: untreated primary wastewater, activated sludge and post-treatment effluent were characterized. From 3163 exact sequence variants (ESVs), 860 were annotated to species-level. In primary wastewater, 28% of ESVs were putative bacterial species previously associated with humans, 14% with animals and 5% as common to the environment. Differential abundance analysis revealed significant relative reductions in ESVs from potentially human-associated species from primary wastewater to activated sludge, and significant increases in ESVs from species associated with nutrient cycling. Between primary wastewater and effluent, 51% of ESVs from human-associated species did not significantly differ, and species such as Bacteroides massiliensis and Bacteroides dorei increased. These findings illustrate that activated sludge increased extracellular protease and urease-producing species, ammonia and nitrite oxidizers, denitrifiers and specific phosphorus accumulators. Although many human-associated species declined, some persisted in effluent, including strains of potential health or environmental concern. Species-level microbial assessment may be useful for understanding variation in wastewater treatment efficiency as well as for monitoring the release of microbes into surface water and the wider ecosystem.

Microplastics removal and characteristics of constructed wetlands WWTPs in rural area of Changsha, China: A different situation from urban WWTPs

Wastewater treatment plants (WWTPs) are important pathways that discharged microplastics into the natural environment, but few relevant research has been conducted in rural areas, especially with horizontal subsurface flow constructed wetlands (HSSFCWs). This study systematically investigates the removal efficiency and characteristics of microplastics in two rural WWTPs with HSSFCW in Changsha city of China and compared the microplastic pollution data of urban and rural WWTPs, to provide some advice for improving the microplastics removal efficiencies in rural WWTPs. 3 L wastewater were collected at each sampling point. Then microplastics in wastewater were extracted by density separation. The size, shape, color, and type of microplastics were analyzed and identified using the integrated microscope and FTIR. The whole experiment was carried out about a month. The results showed that the microplastics removal efficiency of rural WWTP1 was 72.38%, and that of rural WWTP2 was 68.10%, which were lower than that of most urban WWTPs. The microplastics removal efficiency of constructed wetlands in rural WWTP1 was 26.59%, and that in rural WWTP2 was 10.61%. Based on the daily discharge volume and the abundance of microplastics in the effluent of WWTPs, approximately 1.45 ∗ 107 items and 1.73 ∗ 107 items of microplastics were released each day from two rural WWTPs, separately. Fiber was the primary microplastic in both influent and effluent. The polyethylene (PE) and polystyrene (PS) were the main ingredients. The primary source of microplastics in rural WWTPs was inferred as domestic sewage. Microplastics removal efficiencies of rural WWTPs can be improved by regular maintenance, reducing the grid spacing, increasing the hydraulic stay time of biochemical pool, and increasing plant density, changing plant species, or adjusting the size and fill order of matrix in HSSFCWs, which can effectively help to prevent secondary pollution of microplastics from rural WWTPs.

Five Years of Rice Cultivation in Paddy Fields for Treated Water from Humus Bioreactor-Type Rural Wastewater Treatment Plants

Five Years of Rice Cultivation in Paddy Fields for Treated Water from Humus Bioreactor-Type Rural Wastewater Treatment Plants

Identification and removal of sulfhydryl groups from wastewaters

Thiols represent a source of environmental pollution especially wastewater. This work proposed to study the elaboration of cellulose acetate polymer-based membranes for their application in the removal of a sulfhydryl groups of real biological treated wastewaters. The addition of nanoparticles to membranes improves the water purification capacity by promoting a good separation of sulfur, more particularly by ZnO-NPs. We used ultrafiltration membrane-assisted ZnO and TiO2 NPs application on real effluents from different biological treatment plants. We identified the hydrosulfite (thiol) group in wastewater and we used membrane processes ultrafiltration technique for sulfur removal. We evaluated the degradation of sulfur in biological treatment plants in Tunisia: The urban wastewater treatment plant or the conventional plant of Rades Malienne is a secondary biological wastewater treatment plant noted STEP1. The rural wastewater treatment plant based vertical flow planted with Phragmites australis from the Grombalia region noted STEP2 and rural wastewater treatment plant based horizontal flow planted with Phragmites australis from the Grombalia region noted STEP3. STEP1 is found to be more loaded with sulfur. Application of AC-ZnO membrane gives 99.07% and 99.55% of sulfur removal from wastewater of STEP1 and STEP3. STEP3 is 50 times less charged on sulfur than STEP1. We suggested that when the sulfur content is high, this leads to an increase in mineral elements. This could be explained by the interactions between thiols and the major elements that cause mineral pollution.

Decision-making process of partnership in establishing and managing of rural wastewater treatment plants: Using intentional and geographical-spatial location data

The construction of rural wastewater treatment plants (RWTPs) is an effective initiative to achieve sustainable water resources, especially in the rural areas situated upstream of the dams where water and waste substances produced by villages are discharged into the wastewater behind the dams. Neither is the initiative feasible to be launched without the partnership of local people. For this reason, we gained insights into the determinants of villagers’ desire and intention to have a share in the construction and management of RWTPs and determined the best place to locate the RWTPs using Fuzzy Catastrophe Scheme (FCS). The study benefited from the survey of 180 rural people from two villages situated upstream of Alavian dam, Maragheh Township, northwestern Iran. Using the theory of goal-directed behavior (TGDB) and rational choice theory (RCT), we designed a questionnaire, inclusive of the constructs relevant to the hypothetical relationships. The Cronbach's alpha method and discriminant analysis were used to make sure that indicator variables were consistently loaded with pertinent latent variables. The results of PLS-SEM manifested a proper fitted model with the data. As would be hypothesized, attitude towards participation, PBC, positive emotions had a positive impact on desire, which directly influences the intention to participate in the construction and management of RWTPs. To locate RWTPs as geographically and spatially as possible, we made use of suitability index (SI), formulated by the FCS, the resulting evidence demonstrated that the spatial distribution of SI would be classified into five bands using Jenks' optimization method, northwestern areas located in Bands 1 and 2 were appropriate areas, whereas, western and northwestern areas (in Bands 4–5) were caught sight of being not appropriate areas. The implications delivered in conclusion would be useful for the same cases in other parts of the world and further to stimulate rural people to participate in the construction of RWTPs and locate the best area for setting up the plants.

Enhanced nitrogen removal upon the addition of volatile fatty acids from activated sludge by combining calcium peroxide and low-thermal pretreatments

This study investigated a combined low-thermal and CaO2 pretreatment to enhance the volatile fatty acid (VFA) production from waste activated sludge (WAS). The fermentative product was added to a sequencing batch reactor (SBR) as an external carbon source to enhance nitrogen removal. The results showed that the combined pretreatment improved WAS solubilization, releasing more biodegradable substrates, such as proteins and polysaccharides, from TB-EPS to LB-EPS and S-EPS. The maximum VFA production of 3529 ± 188 mg COD/L was obtained in the combined pretreatment (0.2 g CaO2/g VS + 70 °C for 60 min), which was 2.1 and 1.4-fold of that obtained from the sole low-thermal pretreatment and the control test, respectively. Consequently, when the fermentative liquid was added as an external denitrification carbon source, the effluent total nitrogen decreased to Class A of the discharge standard for pollutants in rural wastewater treatment plants in most areas of China.

Wastewater analysis reveals urban, suburban, and rural spatial patterns of illicit drug use in Dalian, China.

Illicit drug use in rural and suburban areas of China has not been studied extensively, as most studies have focused on illicit drug use in urban areas. To compare the differences between urban, suburban, and rural drug use, we collected influent samples from 19 urban, 9 suburban, and 18 rural wastewater treatment plants in Dalian, respectively. A method using solid-phase extraction combined with derivatization for gas chromatography -mass spectrometry analysis was applied to detect biomarker concentrations. The concentrations of methamphetamine and morphine ranged from 3.12 to 605ng/L and < 2.35 to 198ng/L, respectively. Norketamine was found in only four samples (5.56 to 14.5ng/L), while 3,4-methylenedioxymethamphetamine and benzoylecgonine were not detected in any samples. Methamphetamine use in rural areas (16.3mg/day/1000 inhabitant (inh), prevalence: 0.06%) was significantly lower than those in urban (77.1mg/day/1000 inh, prevalence: 0.23%) and suburban (234mg/day/1000 inh, prevalence: 0.70%) areas. Heroin use in suburban areas (57.6mg/day/1000 inh, prevalence: 0.10%) was significantly higher than that in urban (13.9mg/day/1000 inh, prevalence: 0.02%) and rural (8.68mg/day/1000 inh, prevalence: 0.02%) areas. The results indicate relatively low levels of illicit drug use in rural areas of Dalian, related to low incomes and outflow of the working-age population. Illicit drug use was most prevalent in suburban areas of Dalian, which may be influenced by large floating populations and few anti-drug efforts in suburban areas.

Evaluating bioavailability of elements in municipal wastewater sludge (Biosolids) from three rural wastewater treatment plants in East Texas (USA) by a sequential extraction procedure

Biosolids (also known as sludge) are nutrient-rich materials used as soil amendments. A modified Tessier sequential extraction protocol was utilized for speciation and bioavailability of metals in samples from Nacogdoches and Lufkin wastewater sludges (NWWS, LWWS) and the Neches Compost sludge (NCS). Application of five steps (adsorbed, exchangeable, organically bound, carbonate and residual/sulfide) was performed to fractionate 26 elements (macroelements: Ca, Fe, K, Mg, Na, P, S, Li, Cs; microelements: As, B, Ba, Cd, Co, Cu, Hg, Mn, Mo, Pb, Se, V, Zn, Ni, Al, Cr, Sr) in samples via inductively coupled plasma optical emission spectrometry (ICPOES). The proximate amounts for most elements were predominant in the sulfide/residual fractions. Among macroelements 88.62–92.23% of K was found bioavailable vis-à-vis the organically-bound or sulfide fractions. About 100% of Li exists in the sulfide fractions vis-a-vis Group 2A elements. In contrast to microelements and transition metals, about 19–32 % Mo was found readily bioavailable. Additionally, Mo occurred in relatively lesser percent in sulfide/residual fractions vis-à-vis other elements. Cd, Pb, Co, V and Al were the least bioavailable. The percent relative bioavailabilities of microelements varied in the order:Mn > Zn > Cu > Ba > Sr > Pb > V > B > Ni > Co > Cr > V > Mo > Hg > Se > Li > Cd.Assessment of the bioavailability of micro- and macro- elements, is essential to predicting element uptake by plants grown in biosolid amended soils, and the possible environmental exposure levels.

A simple field essay for detecting departures from expected performance in small-scale, remote or rural wastewater treatment plants

A scientific basis is given to the traditional method of inferring effluent quality based on visualization of samples in transparent flasks. A scale of 1-6, with different printed grey intensities, is placed behind transparent PET bottles containing the sample, and gives an indication of the range of turbidity in the sample (1 is the most transparent and can only be visualized if the effluent is well clarified; in the other spectrum, 6 is the darkest and indicates highly turbid effluents). Turbidity has been correlated with total suspended solids (TSS), particulate biochemical oxygen demand (BOD) and particulate chemical oxygen demand (COD) based on thousands of monitored data collected in the effluent from seven different treatment processes in Brazil: upflow anaerobic sludge blanket (UASB) reactor, trickling filters, activated sludge, horizontal wetland, vertical wetland, polishing ponds and coarse filter after pond. The method is simple and instantaneous, can be used in virtually all places and in every visit of the operator to the remote treatment plant, allows recording of the image in smartphones, does not use any equipment, chemicals or energy, and has been showed to represent well the effluent quality of existing treatment plants. This essay is complementary and does not substitute specific traditional sampling and analysis, but allows easy inference of deterioration of effluent quality.

Mitigating rural WWTP impacts: System dynamics modeling of downstream nutrient outputs

A system dynamics modeling approach was used to assess the potential impact of intentional struvite crystallization recovery on wastewater treatment plant (WWTP) allocation of N and P in effluent and biosolids outputs. Struvite crystallization has been used to recover wastewater N and P and produce valuable fertilizer. However, it is often overlooked whether additional benefits may be realized by diverting N and P from other fates. A system dynamics model was used with operational data from three activated-sludge WWTPs in North Florida. Incorporating struvite crystallization reduced the effluent P load by 37 to 100%, dependent upon the WWTP. This may translate into substantial savings for systems facing severe restrictions in effluent P release outside the plant. Additionally, biosolids P load reductions ranged from 17 to 46%. The model also predicted a 37% average increase in the biosolids N:P ratio. Increasing the N:P ratio may allow for greater biosolids land-application rates where P fertilizer restrictions exist. In comparison, the N load reductions were much less dramatic, i.e. below 10% reduction from the effluent and 14% from the biosolids. Most N inputs into an activated-sludge type WWTP are likely lost through denitrification during wastewater processing and struvite does not appear to be a significant means of recovering N from small WWTPs. However, incorporating struvite recovery into even the simplest WWTPs reduces effluent post-treatment needs and results in a more useful biosolids product.

Exploring Elimination Kinetics of Four 5-Nitrofuran Derivatives by Microbes Present in Rural and Municipal Activated Sludge

The wastewater treatment plants (WWTPs) are the biggest reservoirs of pharmaceutical residues discharged into the environment. Among many pharmaceuticals, derivatives of 5-nitrofuran, whose cytotoxicity and neurotoxicity have been proved, are widely used. The ability of such compounds to accumulate in water and sediments motivated us to analyze the ability of microbial communities of rural and municipal WWTPs to eliminate nitrofurantoin (NFT), nitrofurazone (NFZ), furaltadone (FTD), and furazolidone (FZD). Metagenomic analysis of microbial communities in rural and municipal activated sludge has provided information about the bacterial biodiversity in the WWTPs. In both samples, the most dominant phylum in terms of abundance was Proteobacteria followed by Bacteroidetes; however, microbial community of the municipal WWTP exhibited greater biodiversity than the one of the rural WWTP. The results of high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) analysis of the samples and elimination kinetic calculations allowed the determination of FZD, FTD, NFT, and NFZ elimination half-time varying from 104 to 327 h and test system first-order half-lives in the examined WWTP samples (from 31 to 231 h). Moreover, a comparison of the effectiveness of the microbials from two treatment plants, a rural one and a municipal one, revealed the poorer performance of the microbial communities from the smaller, rural WWTP in disposal of the analyzed pharmaceuticals, as after 24 days, the rural WWTP community was able to eliminate from 20 to 62% of 5-nitrofuran derivatives, while the municipal consortium removed over 85% of the compounds from the cultures.

Removal of Bisphenol A and Its Potential Substitutes by Biodegradation

The possibility of removing bisphenol A and its five potential substitutes (bisphenols S, F, AF, E, and B) was tested using microorganism consortia from river water and activated sludge from municipal and rural wastewater treatment plants. For most bisphenols, biodegradation with activated sludge was faster than with river water and a greater extent of biodegradation was also achieved. However, only bisphenol A and bisphenol F underwent 100% primary biodegradation while other bisphenols degraded no more than about 50% which has some important implications in case of their increased usage. Metabolic activity in biodegradation liquors was also tested and it showed higher activity in the tests with activated sludge than with river water. However, there was no clear connection between the decline of metabolic activity and the extent of biodegradation as decreased activity was observed for two easily degrading bisphenols and two others with little biodegradability. It can be assumed that two different phenomena are involved in this process including depletion of nutrients for easily degradable bisphenol A and absence of nutrients for bacteria incapable of primary degradation of bisphenol AF and bisphenol S.

Influent Forecasting for Wastewater Treatment Plants in North America

Autoregressive Integrated Moving Average (ARIMA) is a time series analysis model that can be dated back to 1955. It has been used in many different fields of study to analyze time series and forecast future data points; however, it has not been widely used to forecast daily wastewater influent flow. The objective of this study is to explore the possibility for wastewater treatment plants (WWTPs) to utilize ARIMA for daily influent flow forecasting. To pursue the objective confidently, five stations across North America are used to validate ARIMA’s performance. These stations include Woodward, Niagara, North Davis, and two confidential plants. The results demonstrate that ARIMA models can produce satisfactory daily influent flow forecasts. Considering the results of this study, ARIMA models could provide the operating engineers at both municipal and rural WWTPs with sufficient information to run the stations efficiently and thus, support wastewater management and planning at various levels within a watershed.

Using image processing for determination of settled sludge volume

Determination of the sludge volume index is key to describing the settling characteristics of sludge in the aeration process of wastewater treatment plants (WWTPs). The two core components of this calculation are the settled sludge volume (SSV) and suspended solids. While the measurement procedure for SSV is generally defined by national or international standards, in practice a wide variety of vessel sizes and shapes are used by operators to monitor WWTP performance. Furthermore, differences in how these tests are carried out can lead to poor data, inefficient WWTP operation and a lack of comparable metrics for WWTP operational monitoring. Thus, there is a requirement to improve operational performance of WWTPs to meet the increasingly stringent legislation regarding discharge limits. The aim of this study was to utilise a novel image-processing system (AutoSSV) to (i) determine its efficacy in describing SSV and (ii) measure and compare different methodologies for measurement of SSV. The AutoSSV system was tested using samples from various WWTPs and the results compared to those determined by standard manual measurement. Both standard and modified settlement tests were conducted on 30 mixed liquor samples, with modified settlement tests consistently resulting in lower SSV measurements. Results from the study showed a strong correlation between the SSV measurements provided by the AutoSSV system and results obtained from current manual measurement methods. The proposed technique would help to standardise the measurement in practice and increase the frequency of monitoring, particularly in small-scale rural WWTPs where there may not be permanent operators on site, and thus provide sufficient performance monitoring for efficient and effective operation.