Aeration Basin Research Articles

Detection of Legionella by cultivation and quantitative real-time polymerase chain reaction in biological waste water treatment plants in Norway.

Cases of Legionnaires' disease associated with biological treatment plants (BTPs) have been reported in six countries between 1997 and 2010. However, knowledge about the occurrence of Legionella in BTPs is scarce. Hence, we undertook a qualitative and quantitative screening for Legionella in BTPs treating waste water from municipalities and industries in Norway, to assess the transmission potential of Legionella from these installations. Thirty-three plants from different industries were sampled four times within 1 year. By cultivation, 21 (16%) of 130 analyses were positive for Legionella species and 12 (9%) of 130 analyses were positive for Legionella pneumophila. By quantitative real-time polymerase chain reaction (PCR), 433 (99%) of 437 analyses were positive for Legionella species and 218 (46%) of 470 analyses were positive for L. pneumophila. This survey indicates that PCR could be the preferable method for detection of Legionella in samples from BTPs. Sequence types of L. pneumophila associated with outbreaks in Norway were not identified from the BTPs. We showed that a waste water treatment plant with an aeration basin can produce high concentrations of Legionella. Therefore, these plants should be considered as a possible source of community-acquired Legionella infections.

Energy saving on wastewater treatment plants through improved online control: case study wastewater treatment plant Antwerp-South

This work provides a case study on how activated sludge modelling and computational fluid dynamics (CFD) can help to optimize the energy consumption of a treatment plant that is already equipped with an advanced control based on online nutrient measurements. Currently, aeration basins on wastewater treatment plant Antwerp-South are operated sequentially while flow direction and point of inflow and outflow vary as a function of time. Activated sludge modelling shows that switching from the existing alternating flow based control to a simultaneous parallel feeding of all aeration tanks saves 1.3% energy. CFD calculations also illustrate that the water velocity is still sufficient if some impellers in the aeration basins are shutdown. The simulations of the Activated Sludge Model No. 2d indicate that the coupling of the aeration control with the impeller control, and automatically switching off some impellers when the aeration is inactive, can save 2.2 to 3.3% of energy without affecting the nutrient removal efficiency. On the other hand, all impellers are needed when the aeration is active to distribute the oxygen.

Impact of secondary treatment types and sludge handling processes on estrogen concentration in wastewater sludge

Endocrine-disrupting compounds (EDCs), such as estrogen, are known to be present in the aquatic environment at concentrations that negatively affect fish and other wildlife. Wastewater treatment plants (WWTPs) are major contributors of EDCs into the environment. EDCs are released via effluent discharge and land application of biosolids. Estrogen removal in WWTPs has been studied in the aqueous phase; however, few researchers have determined estrogen concentration in sludge. This study focuses on estrogen concentration in wastewater sludge as a result of secondary treatment types and sludge handling processes. Grab samples were collected before and after multiple treatment steps at two WWTPs receiving wastewater from the same city. The samples were centrifuged into aqueous and solid phases and then processed using solid phase extraction. Combined natural estrogens (estrone, estradiol and estriol) were measured using an enzyme-linked immunosorbent assay (ELISA) purchased from a manufacturer. Results confirmed that activated sludge treatments demonstrate greater estrogen removal compared to trickling filters and mass concentration of estrogen was measured for the first time on trickling filter solids. Physical and mechanical sludge treatment processes, such as gravity thickeners and centrifuges, did not significantly affect estrogen removal based on mass balance calculations. Dissolved air flotation thickening demonstrated a slight decrease in estrogen concentration, while anaerobic digestion resulted in increased mass concentration of estrogen on the sludge and a high estrogen concentration in the supernatant. Although there are no state or federally mandated discharge effluent standards or sludge application standards for estrogen, implications from this study are that trickling filters would need to be exchanged for activated sludge treatment or followed by an aeration basin in order to improve estrogen removal. Also, anaerobic digestion may need to be replaced with aerobic digestion for sludge that is intended for land application.

Experimental Study and Adsorption Modeling of COD Reduction by Activated Carbon for Wastewater Treatment of Oil Refinery

Application of Granular Activated Carbon (GAC) in adsorption process has been studied for the advanced treatment of municipal and industrial wastewater. Because of entering poisonous compounds such as furfural, phenol and sulfides into the oily wastewater of Tehran refinery, biological aeration basins of wastewater treatment unit may not have the desired performance of COD reduction. In this study, GAC is examined for reduction of COD effluent from the Dissolved Air Flotation (DAF) unit to achieve to the environmental and design regulations.The equilibrium batch experiments as well as dynamic adsorption tests were performed to determine the maximum adsorption capacity and the breakthrough curves of COD, respectively. The data derived from equilibrium studies were modeled using Langmuir theory and the isotherm parameters were determined at two different temperatures of 25 and 40 C. Dynamic adsorption modeling was carried out considering the axial dispersion model in the bed of GAC with the assumption of lump kinetic mass transfer and linear driving force into the solid phase. The model results of COD breakthrough curve concentration have shown a fairly good agreement with experimental results. The sensitivity analysis of the dynamic model was carried out at different temperatures, bed lengths, feed flow rate and feed concentration to have a proper insight for appropriate design of a GAC fixed bed.It is concluded that GAC fixed bed could be an auxiliary unit for biological treatment of wastewater to overcome the problems of biological basin in oil refineries.

혼합폐수의 효율적인 처리를 위한 생물학적 처리공정 내의 미생물 군집 특성 분석

Depending on season, mixed wastewater can show great deviations in terms of the influent ratios of tannery and seafood-wastewater. Increases in the ratio of tannery wastewater in influent water also result in increases in the concentration of chromium, which decreases the ratio of BOD/T-N so that the removal efficiency of organic and nitrogen pollutants in biological wastewater treatment deteriorates. No substantial differences occur in the ratios of Eubacteria/total bacteria as the ratio between tannery wastewater and seafood wastewater changes in the influent water. In contrast, the cell numbers and activities of Eubacteria and total bacteria significantly decline with increasing ratios of tannery wastewater in the influent water. Stable removal of organic and nitrogen pollutants by biological wastewater treatments leads to dominance of Proteobacteria groups in all biological treatment basins. In aeration and oxic basins, <TEX>${\gamma}$</TEX>-Proteobacteria account for approximately 21% of the Eubacteria groups, at <TEX>$1.9{\times}10^9{\sim}2.0{\times}10^9$</TEX> cells/mL, while in an anoxic basin, <TEX>${\beta}$</TEX>-Proteobacteria account for approximately 19% of the Eubacteria groups, at <TEX>$1.3{\times}10^9$</TEX> cells/mL. However, a substantial decline in dominance of approximately 11% occurs for <TEX>${\gamma}$</TEX>-Proteobacteria in aeration and oxic basins and about 1% for <TEX>${\beta}$</TEX>-Proteobacteria in an anoxic basin. Mixed wastewater that undergoes extensive property changes of the influent water shows an efficiency of biological treatment that is greatly influenced by the ratio of dominant Proteobacteria groups.

Use of on-site bioreactors to estimate the biotransformation rate of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE) during activated sludge treatment

Accurate rates are needed for models that predict the fate of xenobiotic chemicals and impact of inhibitors at full-scale wastewater treatment plants. On-site rates for aerobic biotransformation of N-ethyl perfluorooctane sulfonamidoethanol (N-EtFOSE), a fluorinated repellent, were determined by continuously pumping mixed liquor from an aeration basin into two well-mixed acrylic bioreactors (4-L) operated in parallel. Known masses of N-EtFOSE and bromide were continuously added to the reactors. Reactor effluents were then monitored for bromide, N-EtFOSE, and metabolites of N-EtFOSE. Of the six transformation products reported in batch studies, only N-ethyl perfluorooctane sulfonamido acetate (N-EtFOSAA) was detected in the effluents. Bromide addition to the reactors enabled rate estimates despite variations in flow rate. Pseudo-second order rate coefficients for the N-EtFOSE biotransformation to N-EtFOSAA, predicted using a dynamic model of the reactor system, were k=2.0 and 2.4Lg−1VSSd−1 for the two reactors, which are slower than the rates previously obtained using batch reactors. Given the relatively slow rate of N-EtFOSE transformation, its sorption and volatilization may be important in wastewater processes. The methodology used in this study should be suitable for similar on-site rate assessments with other contaminants or inhibitors.

Foaming control in activated sludge treatment plants by coagulants addition

This paper presents the results of an investigation that aimed to evaluate the efficiency of various inorganic coagulants and organic polymers to combat filamentous foaming and bulking problems, caused by the proliferation of M. parvicella and/or Gordona amarae. The duration of the investigation covered 14 months. During this period foam samples were taken from the aeration basins of two full-scale wastewater treatment plants that contained high concentrations of M. parvicella and/or Gordona amarae. Bench scale batch experiments were conducted to evaluate the efficiency of the following coagulants: ferric chloride, ferrous chloride, polyaluminium chloride, hydrated aluminium sulphate, cationic polymer. In addition bench scale batch experiments (ammonia uptake rate (AUR) and oxygen uptake rate (OUR) measurements) were conducted to evaluate the toxicity effects of the most promising coagulants on nitrification and organic matter removal. Polyaluminium chloride (PAX) and cationic polymer proved to be the most efficient among all the coagulants investigated. By adding PAX (aluminium application of 6.6 – 11.5 g Al3+ kg-1 MLSS) a general improvement of the settling properties of the activated sludge was achieved. High foaming control was also achieved with cationic polymer addition at doses in the 3.5 to 4.5 g kg-1 MLSS. According to microscopic analysis of the sludge samples following PAX or polymer addition, the floc strength was improved and flocs appeared more compact and dense. In addition both M. parvicella and Gordona amarae filamentous organisms were embedded inside the floc material, making access to particulate and colloidal substrates more difficult due to increased diffusional resistance. PAX or polymer addition, at the above specified doses, resulted in a 75 – 100 % reduction of the sludge foaming potential. PAX potential toxicity was investigated in the context of this study. PAX addition caused no inhibition on autotrophic and heterotrophic bacteria that perform nitrification and organic carbon removal, respectively. The estimated operational costs of PAX and polymer addition for foaming control, are approximately 0.0057 euros m-3 and 0.0026 euros m-3 of wastewater treated, respectively.

Transformation of silver nanoparticles in fresh, aged, and incinerated biosolids

The purpose of this research was to assess the chemical transformation of silver nanoparticles (AgNPs) in aged, fresh, and incinerated biosolids in order to provide information for AgNP life cycle analyses. Silver nanoparticles were introduced to the influent of a pilot-scale wastewater (WW) treatment system consisting of a primary clarifier (PC), aeration basin, and secondary clarifier. The partitioning of the AgNPs between the aqueous and solid phases in the system was monitored. Less than 3% of the total AgNPs introduced into the PC were measured at the overflow of the PC. Biosolids were collected from the pilot-scale system for silver analyses, including Ag concentration and speciation. Additionally, biosolids were collected from a publically owned treatment works (POTW). The POTW biosolids were spiked with AgNPs, AgNO3, and Ag2S. One set of the spiked POTW biosolids was aged for one month, and another set was analyzed within 24 h via X-ray absorption spectroscopy (XAS) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX) in order to determine Ag chemical speciation and elemental associations. Replicates of the aged and 24-h samples were also incinerated at 850 °C for 4 h. The residual ash was analyzed by XAS and SEM-EDX. The results show that AgNPs are converted to Ag-sulfur (as sulfide and sulfhydryl) species in fresh and aged biosolids, which is in agreement with other studies on AgNPs in biosolids. Results from linear combination fitting of the XAS data for incinerated biosolids show that a significant proportion of the spiked silver (30–50%) is converted to elemental Ag in the incineration process. In addition to elemental Ag, the results suggest the presence of additional Ag–S complexes such as Ag2SO4 (up to 25%), and silver associated with sulfhydryl groups (26–50%) in the incinerated biosolids. Incinerated biosolids spiked with AgNO3 and Ag2S exhibited similar transformations. These transformations of AgNPs should be accounted for in life-cycle analyses of AgNPs and in management decisions regarding the disposal of incinerated biosolids.

Taking Denitrification to the Next Level: An Upgrade of Proven Technology With 21st Century I&amp;C

In 2006, one of the largest wastewater reclamation facilities in the northern Virginia area recognized the need to expand the facility from 18 to 24 mgd (million gallons per day). In part, the upgrade was triggered by regulations requiring reduction of Total Nitrogen discharge on an annual basis to 3 mg/L. At the same time, there was a need to replace their plant-wide data acquisition and control system (DACS), with a new modern supervisory control and data acquisition (SCADA) system. This design-build project also provided “limit of technology” nutrient removal; the existing aeration basin volume was doubled and reconfigured to allow operation in either 4-stage Bardenpho or modified ludzack ettinger (MLE) modes; 14 new de-nitrification filters were implemented for a total of 24; and a second/standby chemical analyzer was installed for redundancy purposes. Furthermore, methanol feed was automated to be flow paced and controlled by a proprietary software calculation algorithm. The proprietary software calculation algorithm for control is feed-forward/feed-back based upon flow and influent and effluent nitrate concentrations. This enhanced the operation and reliability of the process and also reduced the risk of methanol overdose by more closely matching the methanol to feed demand. Consistent methanol dose control is challenging when trying to meet low effluent total nitrogen while simultaneously maintaining a low Carbonaceous Biochemical Oxygen Demand (CBOD). This plant is currently in full operation, being controlled by plant staff, and in compliance with the regulation requirements that triggered the plant-wide upgrade in the first place. This paper will discuss the integration of new technologies, the operational benefits, and the startup coordination required to reliably meet the new operating permit limits.

Productive Experiment on Short-Time Aeration Treatment of Municipal Sewage

COD and BOD of the inflow of aeration basin and the effluent of secondary sedimentation tank were detected through orthogonal test.The test use removal rate of COD and BOD as evaluation index, B/C as analysis index. The result of the test indicated that the best working condition can be achieved when there are 3 water pumps for inflow, the concentration of activated sludge stands at 1600mg/L, and HRT in the aeration basin and secondary sedimentation tank stand at 1.86 hours and 2.87 hours respectively. The test demonstrated that short-time aeration can reduce the energy consumption and, therefore, the cost effectively, while insure the effluent reach the outlet qualitative standard. This is suitable for sewage treatment plants in south China since the concentration of their inflow is low.

Characterization of aerosol emissions from wastewater aeration basins

The emission of particulate matter (PM10 and PM2.5) and ammonia (NH3) by aeration processes at wastewater treatment plants (WWTPs) with and without odor control units was examined. Local concentrations of PM2.5, PM10, and NH3 at the aeration basins were within urban ranges. Emission fluxes of NH3 and PM2.5 for a medium-sized WWTP were determined to be 136 g day−1 and 43 g day−1, respectively, which are not substantial emission fluxes for urban environments. Odor control treatment using a granulated activated carbon bed reduced aerosol and NH3 emissions substantially. Detection of sterols, in particular the fecal sterol campesterol, in the PM clearly demonstrates aerosolization of wastewater components in the aeration process. The presence of campesterol in PM2.5 at a remote fenceline location in a WWTP facility illustrates that wastewater components are aerosolized in the fine PM fraction and transported beyond the facilities. Implications: Wastewater treatment plants are potential emission sources of particulate matter and gases. This study characterized particulate matter emissions from aeration basins and quantified emissions fluxes of particulate matter and NH3. While fine and coarse particles as well as NH3 are being emitted, the overall emissions are small compared to other urban sources. However, fecal steroid presence in particles at the fence of a treatment plant demonstrates that wastewater material is getting aerosolized and transported beyond the facilities.

Foaming Scum Index (FSI) – A new tool for the assessment and characterisation of biological mediated activated sludge foams

The formation of thick stable brown foams within the activated sludge process has become a familiar operational problem. Despite much research having already been carried out into establishing the causes of activated sludge foaming there is still no general consensus on the mechanisms involved. Historically investigation into activated sludge foaming has involved either measuring, under aeration conditions, the propensity of mixed liquor samples to foam, or evaluating different physico-chemical properties of the sludge which have previously been linked to activated sludge foaming. Both approaches do not present a means to quantify the risk posed to the treatment plants once foams have started to develop on the surface of aeration basins and final clarifiers. The Foaming Scum Index (FSI) is designed to offer a means to quantify risk on the basis of different foam characteristics which can easily be measured. For example, foam stability, foam coverage, foam suspended solids content and biological composition. The FSI was developed by measuring foam samples taken from several different domestic and municipal wastewater treatment sites located in Greater Dublin area (South-East Ireland). Path analysis was used to predict co-dependencies among the different sets of variables following a number of separate hypotheses. The standardized beta coefficients (β) produced from the multivariate correlation analysis (providing a measure of the contribution of each variable in the structural equation model) was used to finalise the weighting of each parameter in the index accordingly. According to this principal, foam coverage exerted the greatest influence on the overall FSI (β = 0.33), whilst the filamentous bacterial composition in terms of the filament index of foam, provided the least (β = 0.03). From this work it is proposed that the index can be readily applied as a standard tool in the coordination of research into the phenomenon of activated sludge foaming.

Investigation of bacterial community in activated sludge with an anaerobic side-stream reactor (ASSR) to decrease the generation of excess sludge

The goal of this study was to investigate the bacterial community in activated sludge with an anaerobic side-stream reactor (ASSR), a process permitting significant decrease in sludge production during wastewater treatment. The study operated five activated sludge systems with different sludge treatment schemes serving as various controls for the activated sludge with ASSR. Bacterial communities were analyzed by denaturing gradient gel electrophoresis (DGGE), sequencing and construction of phylogenetic relationships of the identified bacteria. The DGGE data showed that activated sludge incorporating ASSR contained higher diversity of bacteria, resulting from long solids retention time and recirculation of sludge under aerobic and anaerobic conditions. The similarity of DGGE profiles between ASSR and separate anaerobic digester (control) was high indicating that ASSR is primarily related to conventional anaerobic digesters. Nevertheless, there was also unique bacteria community appearing in ASSR. Interestingly, sludge in the main system and in ASSR showed considerably different bacterial composition indicating that ASSR allowed enriching its own bacterial community different than that from the aeration basin, although two reactors were connected via sludge recirculation. In activated sludge with ASSR, sequences represented by predominant DGGE bands were affiliated with Proteobacteria. The remaining groups were composed of Spirochaetes, Clostridiales, Chloroflexi, and Actinobacteria. Their putative role in the activated sludge with ASSR is also discussed in this study.

Aeration prevents methyl mercury production in dental wastewater

Although research has demonstrated that Hg is methylated in the reducing conditions of the dental clinic wastewater collection system, studies are inconclusive as to whether further methylation occurs in the aeration basin of activated sludge wastewater treatment plant (WWTP) which typically treats this waste. Given the high levels of methyl Hg reported in dental wastewater (DWW), it is important to determine whether additional methylation occurs once it enters the WWTP. To achieve this objective, we incubated DWW under conditions designed to mimic the oxidized conditions of the activated sludge aeration basin in a WWTP. Duplicate bioreactors were charged with raw DWW collected from a 12-chair dental clinic and incubated both with and without aeration. Aeration was continued for 15 days, consistent with the typical mean cell residence time (MCRT) necessary for both heterotrophic carbon oxidation (typically 5–6 days) and nitrification (typically 12–15 days), thus ensuring that incubation time exceeded those for most conceivable MCRTs used in the activated sludge process. Results demonstrate a rapid increase in pH concomitant with an increase in dissolved oxygen (DO) to near saturation in the aerated reactor. The non-aerated reactor remained low or at zero DO due to low surface reaeration coupled with the high levels of organic matter. The rate of mercury methylation increased in the unaearated reactors rapidly upon incubation, reaching highest levels when DO was at the lowest levels during the experiment. In great contrast, methyl mercury levels were much lower and net mercury methylation does not appear to occur at any significant rate under aeration. These results imply that although some mercury methylation may occur in the sewer collection system (or anaerobic digesters), net methylation is unlikely to occur in the aeration basin in activated sludge WWTPs, and thus methyl Hg influent levels from DWW represent an upper bound on effluent levels.

Evaluation of sampling techniques for detection and quantification of airborne legionellae at biological aeration basins and shower rooms

Inhalation of legionellae aerosolized from biological aeration basins (AB) and shower rooms (SR) has been linked to severe pneumonia and Pontiac fever. However, comprehensive evaluations at these facilities using various bioaerosol sampling techniques are lacking. This study assessed two agar-based (Andersen one-stage sampler and MAS-100/A), three liquid-based (BioSampler, AGI-30 and MAS-100/L) and two filter-based sampling methods (cassette/polycarbonate filter and IOM/gelatin filter) at AB. The BioSampler obtained the highest positive rate of culturable legionellae (8–50%) (P<0.05). As for collecting total and viable legionellae, the IOM consistently showed the highest efficiencies regardless of sampling time (30–270min). When assessing the cassette, BioSampler and AGI-30 at SR, the cassette was more efficient in collecting total and viable legionellae (P<0.05), whereas only the BioSampler and AGI-30 recovered culturable legionellae. The viability percentages (calculated as viable cell counts to total cell counts, 12–77%) were not significantly different between the samplers regardless of sampling location and sampling time (P>0.05). Overall, the IOM and cassette performed better for collecting total and viable legionellae, and culturable legionellae may be detected more frequently by the BioSampler at AB and SR.

Odor control using chemical dosing, coupled with odor monitoring electronic noses on an aeration basin at a WWTP

Odor control using chemical dosing, coupled with odor monitoring electronic noses on an aeration basin at a WWTP

Optimization of Mixing in IFAS and MBBR Aeration Basins using Computational Fluid Dynamics

Optimization of Mixing in IFAS and MBBR Aeration Basins using Computational Fluid Dynamics

Investigation of a new anaerobic side-stream reactor (ASSR) process for sludge reduction in biological wastewater treatment

Investigation of a new anaerobic side-stream reactor (ASSR) process for sludge reduction in biological wastewater treatmentPreliminary research on the anaerobic side-stream reactor (ASSR) process and examination of literature led us to develop the hypothesis that deflocculation and subsequent sludge hydrolysis occur more effectively under the short period of anaerobic digestion and that recirculation of this sludge back to the aeration basin could lead to more effective excess sludge reduction. To verify this...Author(s)Dong-Hyun ChonChul ParkSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Mar, 2012ISSN1938-6478DOI10.2175/193864712811694145Volume / Issue2012 / 2Content sourceResiduals and Biosolids ConferenceCopyright2012Word count286

Nitrogen removal assessment through nitrification rates and media biofilm accumulation in an IFAS process demonstration study

An IFAS demonstration study was conducted at the 76,000 m 3/day (20MGD) James River Wastewater Treatment Plant (JRTP) located in Newport News, Virginia by converting one fully-aerobic conventional aeration basin with dedicated secondary clarification to a 7041 m 3/day (8404 m 3/day max month) IFAS train in a modified Ludzack-Ettinger (MLE) configuration. During the study, biomass concentrations on the biofilm carriers were monitored (weekly) as well as nitrogen species concentrations in the IFAS reactor to quantify the nitrogen transformations occurring within the demonstration tank. In a related effort, nitrification kinetics for ammonia and nitrite oxidizing bacteria were monitored on a weekly basis for IFAS media alone, IFAS process mixed liquor without media, and IFAS mixed liquor and media together in an effort to identify the location of nitrification activity (i.e. on the media or in the suspended culture) in the IFAS process. Biomass quantity on the media was generally observed to be inversely related to temperature except during a period when an auxiliary carbon source contaminated with fungi was introduced. Both ammonia oxidizing and nitrite oxidizing bacterial activity were elevated on the carriers compared to the suspended culture (AOB media: 4.97 mgNOx/gMLSS/hr; AOB suspended: 1.72 mgNOx/gMLSS/hr; NOB media: 7.55 mgNOx/gMLSS/hr; NOB suspended: 0.82 mgNOx/gMLSS/hr) during all periods of the study. In-basin nitrification rates calculated based on nitrogen profiling efforts averaged 0.90 mgNOx/m 2/day which was in good agreement with the average of 0.89 mgNOx/m 2/day for IFAS mixed liquor and media from batch testing.

Calicivirus Removal in a Membrane Bioreactor Wastewater Treatment Plant

To evaluate membrane bioreactor wastewater treatment virus removal, a study was conducted in southwest France. Samples collected from plant influent, an aeration basin, membrane effluent, solid sludge, and effluent biweekly from October 2009 to June 2010 were analyzed for calicivirus (norovirus and sapovirus) by real-time reverse transcription-PCR (RT-PCR) using extraction controls to perform quantification. Adenovirus and Escherichia coli also were analyzed to compare removal efficiencies. In the influent, sapovirus was always present, while the norovirus concentration varied temporally, with the highest concentration being detected from February to May. All three human norovirus genogroups (GI, GII, and GIV) were detected in effluent, but GIV was never detected in effluent; GI and GII were detected in 50% of the samples but at low concentrations. In the effluent, sapovirus was identified only once. An adenovirus titer showing temporal variation in influent samples was identified only twice in effluent. E. coli was always below the limit of detection in the effluent. Overall, the removal of calicivirus varied from 3.3 to greater than 6.8 log units, with no difference between the two main genogroups. Our results also demonstrated that the viruses are blocked by the membrane in the treatment plant and are removed from the plant as solid sludge.