This work describes the development of an intermittently aerated pilot-scale process (V = 0.34 m(3)) operated without oxidized nitrogen recycle and supplemental carbon addition optimized for nitrogen ...removal via nitritation/denitritation. The aeration pattern was controlled using a novel aeration strategy based on set-points for reactor ammonia, nitrite and nitrate concentrations with the aim of maintaining equal effluent ammonia and nitrate + nitrite (NOx) concentrations. Further, unique operational and process control strategies were developed to facilitate the out-selection of nitrite oxidizing bacteria (NOB) based on optimizing the chemical oxygen demand (COD) input, imposing transient anoxia, aggressive solids retention time (SRT) operation towards ammonia oxidizing bacteria (AOB) washout and high dissolved oxygen (DO) (>1.5 mg/L). Sustained nitrite accumulation (NO2-N/NOx-N = 0.36 ± 0.27) was observed while AOB activity was greater than NOB activity (AOB: 391 ± 124 mgN/L/d, NOB: 233 ± 151 mgN/L/d, p < 0.001) during the entire study. The reactor demonstrated total inorganic nitrogen (TIN) removal rate of 151 ± 74 mgN/L/d at an influent COD/ Formula: see text -N ratio of 10.4 ± 1.9 at 25 °C. The TIN removal efficiency was 57 ± 25% within the hydraulic retention time (HRT) of 3 h and within an SRT of 4-8 days. Therefore, this pilot-scale study demonstrates that application of the proposed online aeration control is able to out-select NOB in mainstream conditions providing relatively high nitrogen removal without supplemental carbon and alkalinity at a low HRT.
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.
► Effluent TN averaged 12 mg/L during an IFAS demonstration using an MLE configured process train. ► The activities of both AOB and NOB were elevated on the IFAS carriers compared to the MLSS. ► NOB activity was greater on media relative to MLSS compared to AOB activity between media and MLSS. ► Biomass density and nitrification activity on media were homogenous throughout aeration basin.
This work gives an overview of the state-of-the-art in modelling of short-cut processes for nitrogen removal in mainstream wastewater treatment and presents future perspectives for directing research ...efforts in line with the needs of practice. The modelling status for deammonification (i.e., anammox-based) and nitrite-shunt processes is presented with its challenges and limitations. The importance of mathematical models for considering N
O emissions in the design and operation of short-cut nitrogen removal processes is considered as well. Modelling goals and potential benefits are presented and the needs for new and more advanced approaches are identified. Overall, this contribution presents how existing and future mathematical models can accelerate successful full-scale mainstream short-cut nitrogen removal applications.
•Densification is a novel low-cost wastewater intensification strategy.•Densification can optimize nutrient removal, settleability, and effluent quality.•Size ranges, food-to-microorganism ratio, and ...selector use may be optimized for densification.
Densification is a novel intensification strategy with the potential to improve treatment capacity within existing continuous-flow (CF) water resource recovery facilities at low capital and operating costs and at relatively small particle sizes compared to typical aerobic granular sludge (AGS) systems. To achieve densification, biological selection principles derived from selector design and AGS concepts have been coupled with physical selection via hydrocyclones at full-scale CF facilities to promote the growth and retention of granules. This combination lowers the sludge volume index (SVI) through superior sludge settling and paves the way for optimized nutrient removal and energy efficiency in low dissolved oxygen conditions. This paper sheds light on the benefits of densification. It delves into areas of advancement to further its implementation: hydrocyclone design, selector zone design, operational guidelines, and the target range for particle sizes and granule fractions.
Display omitted
•Immediate improvement in settling characteristic of activated sludge with the implementation of hydrocyclone based wasting.•Densification did not cause a reduction in nitrification capacity as ...expected due to diffusion limitation.•SRT of dense aggregates were double of lighter flocs, resulting in selective retention of nitrifiers and PAOs.•AvN control allowed for low DO operation, facilitating excellent N and P removal.•The presence of denitrifying PAOs was demonstrated, stabilizing biological phosphorus removal.
The James R. Dolorio Water Reclamation Facility in Pueblo, Colorado, uses AvN aeration controls to lower aeration energy while promoting carbon-efficient nutrient removal and hydrocyclone-based wasting to achieve SVI improvements and process intensification. The results from the full-scale installation showed that hydrocyclone-based wasting helped improve settling characteristics by reducing the SVI from 200 ± 52 mL/g to 83 ± 22 mL/g within weeks of operation. PAO and nitrifiers were preferentially retained in dense flocs and granules, while lighter heterotrophic and filamentous organisms were preferentially wasted, thus uncoupling the SRT of these two fractions relative to the overall SRT. The SRT was estimated at 14.4 ± 3.4 days for dense aggregates and 7.1 ± 2.3 days for lighter flocs. The use of AvN control with continuous low DO conditions resulted in low DO conditions (< 0.3 mgO2/L) reducing air demand by 50% while providing excellent nitrogen (effluent TIN < 11 mgN/L) and TP removal (effluent TP < 1 mgP/L) at low primary effluent COD/N ratio of 6.0. The presence of comammox was demonstrated through molecular analysis, while ex-situ batch tests revealed the presence of DPAO, which could have attributed to the energy and carbon-efficient biological nutrient removal.
Display omitted .
Biochar produced from switchgrass via hydrothermal carbonization (HTC) was used as a sorbent for the removal of copper and cadmium from aqueous solution. The cold activation process using KOH at room ...temperature was developed to enhance the porous structure and sorption properties of the HTC biochar. The sorption efficiency of HTC biochar and alkali activated HTC biochar (HTCB) for removing copper and cadmium from aqueous solution were compared with commercially available powdered activated carbon (PAC). The present batch adsorption study describes the effects of solution pH, biochar dose, and contact time on copper and cadmium removal efficiency from single metal ion aqueous solutions. The activated HTCB exhibited a higher adsorption potential for copper and cadmium than HTC biochar and PAC. Experiments conducted with an initial metal concentration of 40 mg/L at pH 5.0 and contact time of 24 h resulted in close to 100% copper and cadmium removal by activated HTCB at 2 g/L, far greater than what was observed for HTC biochar (16% and 5.6%) and PAC (4% and 7.7%). The adsorption capacities of activated HTCB for cadmium removal were 34 mg/g (0.313 mmol/g) and copper removal was 31 mg/g (0.503 mmol/g).
► Biochar prepared via hydrothermal carbonization can be an effective adsorbent. ► Cold alkali activation enhanced the adsorption capacity for copper and cadmium. ► Adsorption by activated biochar was higher than by unactivated biochar and PAC.
This study presents results from the City of St. Petersburg's (Florida) Southwest Water Reclamation Facility. This high‐rate BNR plant (SRT ~ 5 days; HRT < 8 hr) achieves combined bioP and shortcut ...simultaneous nitrification and denitrification (SND) via nitrite in a simple BNR configuration—an anaerobic–aerobic (A/O) process without mixed liquor recycle and a 25% unaerated fraction. N removal to low effluent and nitrate and nitrite (
NO3- +
NO2-) concentrations occurs mainly via SND by operating the aerated zone at low DO, but still achieving near‐complete ammonium (
NH4+) removal. Despite the low DO operation, very good bioP performance is achieved. Full‐scale performance data and detailed bench‐scale testing were conducted to assess the nitrogen and phosphorus removal at low DO conditions. Full‐scale results showed that the plant achieves effluent total inorganic nitrogen (TIN) and total phosphorus (TP) concentrations of approximately 2.0 mgN/L and 0.5 mgP/L, respectively, at an average influent C:N ratio of 7:1 mgCOD:mgN.
Practitioner points
Simple anaerobic–aerobic (A/O) process demonstrated combined N and P removal
Ammonia oxidation was not hampered by low DO (<0.5 mg/L) operation
Low DO (<0.5 mg/L) operation sustained SND via nitrite pathway in a high‐rate process (HRT < 6 hr)
P uptake was demonstrated at low DO which counters to the widely held understanding that high DO (>1.5 mg/L) is necessary
Heterotrophic consumption of nitrite at low DO was the key to the out‐selection of nitrite‐oxidizing bacteria
Good N and P removal performance is acgieved at low DO conditions. Low DO conditions did not affect the nitrification or phosphorus uptakes rates. Low DO operation sustained SND via nitrite pathway. Heterotrophic consumption of nitrite at low DO was the key to the otu‐selection of nitrite‐oxidizing bacteria.
•Biological selection alternates substrate feast and famine and controls SRT.•Carbon-storing heterotrophic bacteria help forming biological aggregates.•Selective biomass wasting with physical ...selection retains biological aggregates.•Biological selection and selective biomass wasting results in hybrid processes.•Mobile biofilms and aerobic granules can be utilized for WWT and BNR.
There have been significant advances in the use of biological and physical selectors for the intensification of continuously flowing biological wastewater treatment (WWT) processes. Biological selection allows for the development of large biological aggregates (e.g., mobile biofilm, aerobic granules, and densified biological flocs). Physical selection controls the solids residence times of large biological aggregates and ordinary biological flocs, and is usually accomplished using screens or hydrocyclones. Large biological aggregates can facilitate different biological transformations in a single reactor and enhance liquid and solids separation. Continuous-flow WWT processes incorporating biological and physical selectors offer benefits that can include reduced footprint, lower costs, and improved WWT process performance. Thus, it is expected that both interest in and application of these processes will increase significantly in the future. This review provides a comprehensive summary of biological and physical selectors and their design and operation.
PDF
