Effluent Total Nitrogen Concentration Research Articles

Laboratory-scale CANON Processes Applied to Wastewater Treatment Plants

A laboratory-scale completely autotrophic nitrogen removal over nitrite (CANON) process was operated in a municipal wastewater treatment plant (WWTP). Sewage effluent treated by the anaerobic/oxic (A/O) process and was used to operate a WWTP to obtain the initial substance for the start-up of a CANON filter reactor. On the 48th day, the ammonia removal rate was measured at greater than 90% in successive 10 d samples and the nitrogen removal rate was greater than 70%. The CANON filter was successful at start up. From the 49th to the 129th day, the dissolved oxygen in the reactor was maintained at fairly low concentration of 0.2-0.5 mg·L-1. The effluent contained nearly no ammonia and the maximum total nitrogen (TN) concentration was 15.6 mg·L-1, which exceeded the national Class 1A Discharge Standards for pollutants from municipal wastewater treatment plants. Nitrite oxidizing bacteria (NOB) proliferated excessively in the reactor. Backwash was implemented on 129th, 169th and 213th days. The nitrogen removal rate was more than 70% for a long time and TN concentration in effluent was below 12 mg·L-1. The nitrogen concentration in effluent fitted the national Class 1A Discharge Standards and the NOB were effectively inhibited. These results show that backwash has negligible on the structure of filter and its impact on the thickness of the bio-membrane and its functional bacteria was small, however, it is capable of effectively inhibiting the activity of the NOB. Periodically backwashing can be utilized as an engineering application to maintain stable operation of the CANON process.

Enhancing nitrogen removal efficiency in a dyestuff wastewater treatment plant with the IFFAS process: the pilot-scale and full-scale studies.

The activated sludge (AS) process is widely applied in dyestuff wastewater treatment plants (WWTPs); however, the nitrogen removal efficiency is relatively low and the effluent does not meet the indirect discharge standards before being discharged into the industrial park's WWTP. Hence it is necessary to upgrade the WWTP with more advanced technologies. Moving bed biofilm processes with suspended carriers in an aerobic tank are promising methods due to enhanced nitrification and denitrification. Herein, a pilot-scale integrated free-floating biofilm and activated sludge (IFFAS) process was employed to investigate the feasibility of enhancing nitrogen removal efficiency at different hydraulic retention times (HRTs). The results showed that the effluent chemical oxygen demand (COD), ammonium nitrate (NH4+-N) and total nitrogen (TN) concentrations of the IFFAS process were significantly lower than those of the AS process, and could meet the indirect discharge standards. PCR-DGGE and FISH results indicated that more nitrifiers and denitrifiers co-existed in the IFFAS system, promoting simultaneous nitrification and denitrification. Based on the pilot results, the IFFAS process was used to upgrade the full-scale AS process, and the effluent COD, NH4+-N and TN of the IFFAS process were 91-291 mg/L, 10.6-28.7 mg/L and 18.9-48.6 mg/L, stably meeting the indirect discharge standards and demonstrating the advantages of IFFAS in dyestuff wastewater treatment.

Achieving partial nitrification in a continuous post-denitrification reactor treating low C/N sewage

To achieve advanced nitrogen removal from municipal sewage with a low carbon/nitrogen (C/N) ratio, a novel Sludge Double Recirculation- Anaerobic/Aerobic/Anoxic process (SDR-AOA) was developed in a continuous-flow reactor. Low C/N (3.19 in average) sewage with the chemical oxygen demand (COD) concentration of 180.14 mg/L and the total nitrogen (TN) concentration of 56.19 mg/L was applied for long-term treatment in the SDR-AOA process. Results showed that, the average nitrite concentration in the effluent of the aerobic zone was increased from 0.15 mg/L (phase 1) to 16.46 mg/L (phase 3), and the nitrite accumulation ratio (NAR) remained between 85.87% and 94.85% in phase 3, for which the TN removal efficiency was increased from 91.40% (C/N: 5.14) to 95.60% (C/N: 3.19), and the low effluent TN concentrations was as low as 2.47 mg/L. The inhibitory effect of anoxic disturbance on nitrite oxidizing bacteria (NOB) might contribute to the effectiveness of partial nitrification, with the percentage of NOB accounting for total bacteria being declined from 4.66% (day 79) to 1.51% (day 135) on the genus level. Nitrogen mass balance analysis demonstrated that 27.77% of TN was removed through simultaneous nitrification and denitrification in the aerobic zone, while the remaining TN (62.25%) was removed through endogenous denitrification in the post-anoxic zone. Further Illumina MiSeq sequencing analysis demonstrated that the predominant bacteria were Rhodocyclaceae, Saprospiraceae and Comamonadaceae on the family level, and they were the key to nitrogen removal processes. In the end, the advanced nitrogen removal was realized in the SDR-AOA process for treating low C/N municipal sewage through the successful achievement of partial nitrification and endogenous denitrification.

Evaluation of Nitrogen Concentration in Final Effluent of Advanced Nitrogen-Removal Onsite Wastewater Treatment Systems (OWTS)

Advanced nitrogen (N)-removal onsite wastewater treatment systems (OWTS) are installed in coastal areas throughout the USA to reduce N loading to groundwater and marine waters. However, final effluent total nitrogen (TN) concentration from these systems is not always routinely monitored, making it difficult to determine the extent to which they contribute to N loads. We monitored the final effluent TN concentration of 42 advanced N-removal OWTS within the Greater Narragansett Bay Watershed, Rhode Island between March 2015 and August 2016. The compliance rate with the State of Rhode Island final effluent standard (TN ≤ 19 mg N/L) was 64.3, 70.6, and 75.0% for FAST, Advantex, and SeptiTech systems, respectively. The median (range) final effluent TN concentration (mg N/L) was 11.3 (0.1–41.6) for SeptiTech, 14.9 (0.6–61.6) for Advantex, and 17.1 (0.6–104.9) for FAST systems. Variation in final effluent TN concentration was not driven by temperature; TN concentrations plotted against effluent temperature values resulted in R 2 values of 0.001 for FAST, 0.007 for Advantex, and 0.040 for SeptiTech systems. The median effluent TN concentration for all the systems in our study (16.7 mg N/L) was greater than reported for Barnstable County, MA systems (13.3 mg N/L), which are monitored quarterly. Depending on technology type, ammonium (NH4 +), nitrate (NO3 −), alkalinity, forward flow, biochemical oxygen demand (BOD), and effluent temperature best predicted effluent TN concentrations. Service providers made adjustments to seven underperforming systems, but TN was reduced to 19 mg N/L in only two of the seven systems. Advanced N-removal OWTS can reduce TN to meet regulations, and monitoring of these systems can enable service providers to proactively manage systems. However, improvement of performance may require recursive adjustments and long-term monitoring.

Effect of phosphorus on nitrogen migration and transformation in deep subsurface wastewater infiltration systems.

This paper investigates the effect of phosphorus on nitrogen migration and transformation during the sewage purification processes in deep subsurface wastewater infiltration systems. Good performance was achieved with a hydraulic loading rate of 0.1 m3/m2·d, indicating that the effluent water quality could meet the primary grade A values as put forth by the 'Cities Sewage Treatment Plant Pollutant Discharge Standard' (GB18918-2002). In addition, the results of three inflow total phosphorus (TP) concentrations (5 mg L-1, 15 mg L-1, and 30 mg L-1) indicated that high-levels of phosphorus were more advantageous in regards to improving the activity of denitrifying bacteria in soil and strengthening the effect of nitrogen removal, suggesting that the effluent total nitrogen (TN) concentration could meet the primary grade A standard (TN ≤ 15 mg L-1). It was further observed that soil depth was less crucial when inflow TP concentrations were higher. Therefore, the results indicated that inflow phosphorus concentrations could greatly influence nitrogen migration and transformation in deep subsurface wastewater infiltration systems.

Evaluation of mainstream nitrogen removal by simultaneous partial nitrification, anammox and denitrification (SNAD) process in a granule-based reactor

The mainstream anaerobic ammonium oxidation (anammox) has attracted extensive attention recently, particularly due to its potential of transforming current wastewater treatment plants from energy consuming to energy neutral or positive. However, the presence of biodegradable chemical oxygen demanding (COD, 20–80mgCODL−1) in the mainstream anammox reactor stimulates the growth of heterotrophic bacteria, which would compete for oxygen with ammonia-oxidizing bacteria (AOB) and for nitrite with anammox bacteria, thus interfering with the autotrophic nitrogen removal process. In the present work, with consideration of granule size distribution, a one-dimensional model describing the mainstream simultaneous partial nitrification, anammox and denitrification (SNAD) in a granule-based reactor was established, calibrated and validated, based on the long-term experimental results. Through applying the verified model, simulation studies were conducted and the results showed that the effluent total nitrogen concentration of <5mgNL−1 could be achieved at C/N ratio of 0.2–0.6, DO concentration of 0.2–0.4mgL−1 and granule radius of 300–600μm. The combined effects indicated that the SNAD process with TN removal efficiency >90% was obtained at C/N ratio and DO concentration of 0.2–1.0 and 0.2–0.4mgO2L−1 respectively. Finally, the various granule size distribution patterns were simulated, which confirmed that the size distribution needed to be incorporated in the model to accurately describe the granular anammox system, considering a model based on a uniform granule size does not reflect the real situations. These results provide guides to optimize the operation of mainstream granular autotrophic nitrogen removal process.

Heterotrophic Ammonia and Nitrate Bio-removal Over Nitrite (Hanbon): Performance and microflora

A novel Heterotrophic Ammonia and Nitrate Bio-removal Over Nitrite (Hanbon) process, combining Short Nitrate Reduction (SNR) with Anaerobic Ammonia Oxidation (Anammox), was developed in a lab-scale continuous up-flow reactor. The substrate effects were investigated to characterize the performance of Hanbon process, and the corresponding microflora information was also revealed. Our results showed that the optimal substrate ratio of NH4+-N:NO3−-N:COD for the Hanbon process was 0.65:1:2.2. The volumetric nitrogen removal rate was up to 9.0 ± 0.1 kgN·m−3·d−1 at high influent substrate concentrations of NH4+-N 375 mg L−1, NO3−-N 750 mg L−1 and COD 1875 mg L−1, which was superior to the reported values of analogous processes. Moreover, the effluent total nitrogen concentration was able to meet the strict discharge standard (less than 10 mg L−1) at low influent substrate concentration of NH4+-N 26 mg L−1, NO3−-N 40 mg·L−1and COD 88 mg L−1. Illumina-based 16S rRNA gene sequencing results showed that Halomonas campisalis and Candidatus Kuenenia stuttgartiensis were the dominant bacteria in the SNR section and Anammox section at high substrate concentration condition. However, Halomonas campaniensis and Candidatus Brocadia brasiliensis were raised significantly at low substrate concentration condition. Hanbon process provided in the present work was flexible of treating wastewater with various nitrogen concentrations, deserving further development.

Effect of Temperature on Nitrogen Removal Performance of Marine Anaerobic Ammonium Oxidizing Bacteria

The effect of temperature on the nitrogen removal performance of marine anaerobic ammonium oxidizing bacteria processing sewage seawater was studied by employing an ASBR reactor, and the dynamic characteristics of the marine anaerobic ammonium oxidizing bacteria at different temperatures were simulated by modified Logistic model. The experimental results indicated that the nitrogen removal performance was affected little at 25-35℃. The total nitrogen removal efficiency (TNRE) remained at (82±2)% and the total nitrogen removal rate (TNRR) was stabilized at (0.62±0.01) kg·(m3·d)-1. When the temperature was 20℃, TNRE increased from 59% at the beginning to 79% after 13 days. This indicated that the marine anammox bacteria still had strong ability of nitrogen removal, and the reactor in the low temperature treatment of sewage containing seawater had a good potential. However, when the temperature dropped to 10-15℃, the nitrogen removal performance of the reactor was inhibited. TNRE decreased to (40±8)% and (11±4)%, respectively. Besides, TNRR also decreased to (0.30±0.04) kg·(m3·d)-1 and (0.08±0.03) kg·(m3·d)-1, respectively. According to the Arrhenius equation, the activation energy for marine anaerobic ammonium oxidation reaction was 26 kJ·mol-1 at 25-35℃, and the activation energy of marine anaerobic ammonium oxidation reaction was 76 kJ·mol-1 at 10-25℃. In addition, dynamic analysis was performed by Logistic model and the NRE and effluent total nitrogen concentration (ceff) at different temperatures were forecasted. The correlation coefficient R2 was between 0.9668 and 0.9957.

Enhanced nutrients removal from municipal wastewater through biological phosphorus removal followed by partial nitritation/anammox

Conventional biological removal of nitrogen and phosphorus is usually limited due to the lack of biodegradable carbon source, therefore, new methods are needed. In this study, a new alternative consisting of enhanced biological phosphorus removal (EBPR) followed by partial nitritationanammox (PN/A), is proposed to enhance nutrients removal from municipal wastewater. Research was carried out in a laboratory-scale system of combined two sequencing batch reactors (SBRs). In SBR1, phosphorus removal was achieved under an alternating anaerobic-aerobic condition and ammonium concentration stayed the same since nitrifiers were washed out from the reactor under short sludge retention time of 2–3 d. The remaining ammonium was further treated in SBR2 where PN/A was established by inoculation. A maximum of nitrogen removal rate of 0.12 kg N∙m–3∙d–1 was finally achieved. During the stable period, effluent concentrations of total phosphorus and total nitrogen were 0.25 and 10.8 mg∙L–1, respectively. This study suggests EBPR-PN/A process is feasible to enhance nutrients removal from municipal wastewater of low influent carbon source. Open image in new window

Complete nitrogen removal by simultaneous nitrification and denitrification in flat-panel air-cathode microbial fuel cells treating domestic wastewater

Microbial fuel cells (MFCs) can treat organic compounds from domestic wastewater without aeration, but an additional procedure is required to remove nitrogen. This study developed a flat-panel air-cathode MFC (FA-MFC) that was comprised of five MFC units connected in series and operated to remove organic and nitrogen compounds from domestic wastewater with a short hydraulic retention time (HRT) of 2.5h. During eight months of operation, the removal efficiencies of chemical oxygen demand (COD) and total nitrogen (TN) increased, reaching 85% and 94%, respectively, and the effluent COD and TN concentrations were 20.7±2.5mg/L and 1.7±0.1mg/L, respectively. The greatest removals of COD and TN were in the first and second unit (0.62kg-N/m3/d of TN removal rate). The FA-MFC system allowed simultaneous removals of COD and TN from domestic wastewater, although it led to minimal power output (6.3W/m3 in the first unit). Because any abiotic ammonia loss was not found under the supplied potential of∼1.1V at a short HRT of 30min, the biological nitrogen removal was thought as a dominant mechanism for TN removal in the FA-MFCs. Microbial community analysis revealed that, near the cathode, Nitrosomonas-like strains contributed to nitrification and Nitratireductor-like strains led to denitrification. Acidovorax-like strains, known for their metabolic diversity, were ubiquitous and appeared to contribute to organics and nitrogen removal in anode and cathode biofilms. This study provides proof of concept that the FA-MFC system has a promise for energy sustainable wastewater treatment.

Use of an integrated biophysical process for the treatment of halo- and nitro- organic wastes

This study assessed the use of an integrated biophysical process incorporating the addition of powdered activated carbon (PAC) to a dual-sludge biological process, in order to improve the removal of problematic contaminants from complex herbicides production wastewater. The main focus was on the removal of nitrogen compounds, total organic carbon (TOC), and halogenated organics (AOX). The dual-sludge pilot setup comprised a conventional activated sludge (CAS) system followed by a membrane bioreactor (MBR) system. The dilution ratio of raw wastewater was gradually decreased (with groundwater) from 0.8 to 0 (no dilution), and PAC was added in the last phase of the study to maintain an equilibrium concentration of 2000 mg/L. PAC addition stimulated a high and steady removal (98%) of the ammoniacal nitrogen, conforming to the sea discharge limit of 5 mg/L. However, the effluent concentrations of total nitrogen, TOC, and AOX were still above the stringent discharge limits of 20, 100 and 0.5 mg/L respectively. Furthermore, it was shown that synergistic effect of various toxic organic compounds, rather than mineral salinity, was the major cause for the acute inhibitions of nitrification and AOX removal. The study showed that the proposed process can function as an efficient treatment system for the complex wastewater typically produced in the herbicide industry, however, it is recommended that complementary physico-chemical treatment steps be added to the treatment process.

A coupled system of half-nitritation and ANAMMOX for mature landfill leachate nitrogen removal

ABSTRACTA coupled system of membrane bioreactor-nitritation (MBR-nitritation) and up-flow anaerobic sludge blanket-anaerobic ammonium oxidation (UASB-ANAMMOX) was employed to treat mature landfill leachate containing high ammonia nitrogen and low C/N. MBR-nitritation was successfully realized for undiluted mature landfill leachate with initial concentrations of 900–1500 mg/L and 2000–4000 mg/L chemical oxygen demand. The effluent concentration and the accumulation efficiency were 889 mg/L and 97% at 125 d, respectively. Half-nitritation was quickly realized by adjustment of hydraulic retention time and dissolved oxygen (DO), and a low DO control strategy could allow long-term stable operation. The UASB-ANAMMOX system showed high effective nitrogen removal at a low concentration of mature landfill leachate. The nitrogen removal efficiency was inhibited at excessive influent substrate concentration and the nitrogen removal efficiency of the system decreased as the concentration of mature landfill leachate increased. The MBR-nitritation and UASB-ANAMMOX processes were coupled for mature landfill leachate treatment and together resulted in high effective nitrogen removal. The effluent average total nitrogen concentration and removal efficiency values were 176 mg/L and 83%, respectively. However, the average nitrogen removal load decreased from 2.16 to 0.77 g/(L d) at higher concentrations of mature landfill leachate.

Technical Performance and Environmental Effects of the Treated Effluent of Wastewater Treatment Plants in the Shenzhen Bay Catchment, China

Technical performance and effluent environmental impact of seven wastewater treatment plant (WWTPs) in the Shenzhen Bay Catchment, China were examined. All WWTPs had good performance in the removal of chemical oxygen demand, biochemical oxygen demand, and suspended solids, while total nitrogen and total phosphorus removal should be enhanced to improve the comprehensive pollutants removal loading rate. The effluent eutrophication effect from WWTPs was in the range of 0.0028–0.0092 kg/m3, and nitrate was the major contributor. The effluent greenhouse gas emission of WWTP1–7 was in the range of 3.23 × 10−5–8.70 × 10−5 kg·CO2/m3. The effluent eutrophication effects and greenhouse gas emission of WWTPs could be reduced by decreasing the effluent total nitrogen concentration. The ecological risk and healthy risk of heavy metals were low. Among examined heavy metals, lead contributed the most to the ecological risk while arsenic contributed most to the human health risk. The human health risk of microbial pollutants of WWTPs1–7 was in the range of 0.0024–0.0042 DALY (Disability Adjusted Life Years). Finally, an ecosystem-based WWTP framework was proposed to systematically include all environmental effects so as to support the sustainable development of WWTPs.

Uncoupling the solids retention times of flocs and granules in mainstream deammonification: A screen as effective out-selection tool for nitrite oxidizing bacteria

This study focused on a physical separator in the form of a screen to out-select nitrite oxidizing bacteria (NOB) for mainstream sewage treatment. This separation relied on the principle that the NOB prefer to grow in flocs, while anammox bacteria (AnAOB) reside in granules. Two types of screens (vacuum and vibrating) were tested for separating these fractions. The vibrating screen was preferred due to more moderate normal forces and additional tangential forces, better balancing retention efficiency of AnAOB granules (41% of the AnAOB activity) and washout of NOB (92% activity washout). This operation resulted in increased NOB out-selection (AerAOB/NOB ratio of 2.3) and a total nitrogen removal efficiency of 70% at influent COD/N ratio of 1.4. An effluent total nitrogen concentration <10mgN/L was achieved using this novel approach combining biological selection with physical separation, opening up the path towards energy positive sewage treatment.

Nitrogen Removal of Municipal Wastewater by ANAMMOX Coupled Shortcut Nitrification in Anaerobic Baffled Reactor

If the technology of anaerobic ammonium oxidation(ANAMMOX) can substitute the mainstream technology of municipal wastewater treatment plant, the energy of municipal wastewater treatment will be decreased significantly. Thus, anaerobic baffled reactor(ABR) was used to build carbon system, shortcut nitrification system and anaerobic ammonia oxidation system. And the three systems were coupled to shortcut nitrification-anaerobic ammonia oxidation reactor to treat municipal wastewater. The results showed that the average effluent COD concentration of carbon removal system was 80 mg·L-1 when the hydraulic retention time of carbon removal system was 4.5 h. And the subsequent shortcut nitrification system would not be adversely affected by the effluent COD. Finally, the average effluent total nitrogen concentration was 10 mg·L-1, with total nitrogen volume load of ANAMMOX system of 0.36 kg·(m3·d)-1. When the dissolved oxygen was controlled between 1 to 2 mg·L-1, the nitrite accumulation rate could be maintained around 90%, ensuring the stable operation of the subsequent anaerobic ammonia oxidation system. The nitrogen of municipal wastewater could be stable and efficiently removed by the shortcut nitrification -ANAMMOX integration ABR with temperature of 30℃ and dissolved oxygen of 1-2 mg·L-1.

Effect of Biofilm Density on Nitrous Oxide Emissions and Treatment Efficiency on Sequencing Batch Biofilm Reactor

The reduction of nitrous oxide (N2O) emission during nitrogen removal process in municipal wastewater treatment is of great urgency. Sequencing batch biofilm reactor (SBBR) system could be a promising and efficient way to solve the problem. In order to get the high chemical oxygen demand (COD) and nitrogen removal efficiency and low nitrous oxide emission, the influence of biofilm density on SBBR was investigated. When the biofilm density changed from 15 to 30 %, the effluent COD, total nitrogen (TN) and ammonia nitrogen decreased, but the effluent TN concentration did not meet the class I-B standard of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant in China. COD, TN, and ammonia nitrogen concentration was 42.34, 19.14 and 2.97 mg/L at 50 % biofilm density. When the density turned from 50 to 70 %, although the effluent COD, TN, and ammonia nitrogen were still decreased, N2O emission increased from 0.45 to 0.77 %. Considering the effluent quality and N2O emission, the optimal biofilm density in SBBR was 50 %.

Pilot-Scale Study of an Integrated Membrane-Aerated Biofilm Reactor System on Urban River Remediation

Coupled with the hydrolysis–acidification (H–A) process, the two-stage continuous flow membrane-aerated biofilm reactor (MABR) system was designed for urban river treatment, and parameter optimization was investigated in accordance with the average effluent concentrations of chemical oxygen demand (COD), ammonia nitrogen (NH4+–N), total nitrogen (TN), and suspended solids (SS). The optimal process parameters included temperature, 19 °C; pH, 8.0; the reflux ratio, 200%; and hydraulic retention time (HRT), 15 h, based on which the operational feasibility of the integrated system was further evaluated during the 40 days pilot-study for the urban river treatment. Results indicated that the integrated system exhibited highly effective performance for the urban river remediation with ∼87% COD removed and >95% NH4+–N removed. Nitrification and denitrification were simultaneously achieved inside the system. The TN removal process was enhanced by the reflux system with the effluent TN concentration remaining at ∼1...

Driving forces of effluent nutrient variability in field scale bioretention

Nutrient exports from urbanized watersheds have been identified as a major contributor to surface water degradation worldwide. As efforts to implement stormwater treatment controls, such as bioretention, become increasingly common, understanding how the functionality of these systems varies based on environmental conditions is critical. Quantifying this variability and its causes will aid in developing more robust models and watershed restoration plans which incorporate the uncertainty of bioretention function. This study investigated effluent nutrient concentrations from ten bioretention areas in North Carolina, USA. Nitrogen species were found to have higher variability than phosphorus species, with changes in effluent concentrations being significantly influenced by environmental conditions. In particular, effluent concentrations of total nitrogen (TN) and nitrate (NO3-N) were strongly correlated to antecedent rainfall depth and temperature. As antecedent rainfall depth increased, NO3-N and TN concentrations decreased. These trends have been noted in other laboratory-based studies and are logical based on the influence of dry conditions on microbial communities. Increases in ambient temperature were shown to increase effluent TN and NO3-N concentrations in conventionally drained systems. However, a negative correlation was found between temperature and effluent NO3-N concentrations in systems with an internal water storage (IWS) layer, suggesting increased denitrifying microbe activity. These results show that variability in effluent nutrient concentrations can be explained by environmental conditions, and that the effects of these conditions may differ based on system design.

Performance of constructed wetland applied for domestic wastewater treatment: Case study at Boimorto (Galicia, Spain)

The study aims at evaluating the performance of a horizontal subsurface flow constructed wetland used for secondary treatment of domestic wastewater since May 2011 at Galicia (Spain). A septic tank was used as primary treatment. The wetland consists of two cells in parallel: cell-A with 350m2 and cell-B with 280m2, constructed with a depth of 0.6m, filled with gravel of 30mm of average size and planted with common reeds. The performance of wastewater treatment was controlled from June 2011 to September 2015. The rural agglomeration is served by a gravity sewer system with high rates of infiltration/inflow during wet weather. Thus, concentration and flow rate of wastewater have high seasonal variability. Average primary effluent BOD5, COD, suspended solids (TSS), total nitrogen (TN) and total phosphorous (TP) concentrations (in mg/L) were: 105, 197, 43, 29 and 3.4, respectively. Meanwhile, average secondary effluent BOD5, COD, SS, TN and TP values (in mg/L) were: 19, 44, 12, 14.3 and 1.9, respectively. A 2.2 log unit reduction for faecal coliforms was observed in the global system. The wetland required to be harvested at the end of each October. The sludge produced by the septic tank has not yet required to be removed. The wetland system presented no problems for vectors or nuisance odours.

Feasibility of enhancing the DEnitrifying AMmonium OXidation (DEAMOX) process for nitrogen removal by seeding partial denitrification sludge

The recently proposed DEnitrifying AMmonium OXidation (DEAMOX) process combined anaerobic ammonia oxidation (ANAMMOX) with denitrification to convert nitrate to nitrite, which was a promising way for treating wastewater containing nitrate and ammonia. This study investigated the feasibility of establishing DEAMOX process by seeding partial denitrification sludge (NO3− → NO2−) using sodium acetate as an electron donor in a sequencing batch reactor. Results showed that the DEAMOX process was established successfully and operated stably in 114-days operation. The average effluent total nitrogen concentration was below 5 mg L−1 and TN removal efficiency reached up to 97% at COD/NO3− ratio of 3.0 under initial NH4+ concentration of 25 mg L−1 and NO3− of 30 mg L−1. It suggested that the presence of NO2− in the system supplied for ANAMMOX and the relatively long sludge retention time (SRT) for denitrifiers were attributed to commendable coexistence of ANAMMOX and denitrifying bacteria.