Real Domestic Sewage Research Articles

WASTEWATER CHARACTERIZATION AND SEQUENCING BATCH REACTOR OPERATION FOR AEROBIC GRANULAR SLUDGE CULTIVATION

Studying the possibility of forming aerobic granules on real domestic sewage was a logical step in the scaling-up process and development of Aerobic Granular Sludge (AGS) technology. It was noted that influent wastewater composition and Sequencing Batch Reactor (SBR) operation cycle time are important factors that can influence the formation of AGS. Therefore, this study aims to determine the suitability of influent wastewater from Bunus Wastewater Treatment Plant (WWTP) for AGS cultivation and then propose a proper SBR operation cycle time. In this study, wastewater characterization was done for the influent of wastewater treatment plant located in Bunus, Kuala Lumpur. The result was then analysed and compared with previous research to determine the suitability of AGS cultivation. The information on SBR from previous studies were also gathered to propose SBR operation cycle time that suit the Bunus WWTP influent. The findings indicate that the wastewater can be characterized as low strength domestic wastewater with low organic and nutrients content. The values of related parameters in this study have shown that influent wastewater of Bunus WWTP is suitable for cultivating AGS. For the proposed SBR operation, the cycle time is 3h, which consist of 60 min (fill), 110 min (aerate), 5 min (settle), and 5 min (discharge), respectively.

Effect of Substrate Ratio on Removal of Nitrogen and Carbon Using Anaerobic Ammonium Oxidation and Denitrification

Real domestic sewage was treated in a sequencing batch reactor (SBR). When the partial nitrification of SBR was achieved, the effluent was fed with quantitative NaNO2, which served as the influent of the anaerobic ammonium oxidation (ANAMMOX) process of the anaerobic SBR (ASBR). The effect of different substrate ratios on the removal of nitrogen and carbon using anaerobic ammonium oxidation and denitrification was investigated under conditions with a temperature of 24℃ and pH of 7.2±0.2. The results showed that ① the nitrogen removal efficiency was optimum when the influent NO2--N/NH4+-N was 1.4-1.6. The average effluent concentrations of NH4+-N, NO2--N, and chemical oxygen demand (COD) were 2.14, 1.07, and 30.50 mg·L-1, and their removal rates were 93.62%, 97.79%, and 74.75%, respectively. The △NO2--N/△NH4+-N and △NO3--N/△NH4+-N ratios were 1.60 and 0.17, respectively. Total nitrogen was removed by the joint action of denitrifying and ANAMMOX bacteria. ② When the influent ratio of NO2--N/NH4+-N increased, the contribution of ANAMMOX to nitrogen removal decreased, but the contribution of heterotrophic denitrification to nitrogen removal increased gradually. ③ The NH4+-N and NO2--N degradation processes corresponded with zero-order reactions and fitted the linear relationship in the typical cycle. Their specific degradation rates were 0.404 and 0.599 mg·(g·h)-1, respectively. Their ratio was 1.48, and the specific degradation rate of COD gradually increased.

Optimization of denitrifying phosphorus removal in a pre-denitrification anaerobic/anoxic/post-aeration + nitrification sequence batch reactor (pre-A2NSBR) system: Nitrate recycling, carbon/nitrogen ratio and carbon source type

Because the efficiency of biological nutrient removal is always limited by the deficient carbon source for the low carbon/nitrogen (C/N) ratio in real domestic sewage, the denitrifying phosphorus removal (DNPR) was developed as a simple and efficient method to remove nitrogen and phosphorous. In addition, this method has the advantage of saving aeration energy while reducing the sludge production. In this context, a pre-denitrification anaerobic/anoxic/post-aeration + nitrification sequence batch reactor (pre-A2NSBR) system, which could also reduce high ammonia effluent concentration in the traditional two-sludge DNPR process, is proposed in this work. The pre-A2NSBR process was mainly composed of a DNPR SBR and a nitrifying SBR, operating as alternating anaerobic/anoxic/post-aeration + nitrification sequence. Herein, the long-term performance of different nitrate recycling ratios (0–300%) and C/N ratios (2.5–8.8), carbon source type, and functional microbial community were studied. The results showed that the removal efficiency of total inorganic nitrogen (TIN, including NH4+-N, NO2– -N, and NO3– -N) gradually increased with the nitrate recycling ratios, and the system reached the highest DNPR efficiency of 94.45% at the nitrate recycling ratio of 300%. The optimum C/N ratio was around 3.9–7.3 with a nitrogen and phosphorus removal efficiency of 80.15% and 93.57%, respectively. The acetate was proved to be a high-quality carbon source for DNPR process. The results of fluorescence in situ hybridization (FISH) analysis indicated that nitrifiers and phosphorus accumulating organisms (PAOs) were accumulated with a proportion of 19.41% and 26.48%, respectively.

Effect of HRT on Nitrogen Removal Using ANAMMOX and Heterotrophic Denitrification

Real domestic sewage was first treated in SBR and partial nitrification was achieved. When average concentrations of NH4+-N, NO2--N, and COD were 37.27, 39.97, and 120 mg·L-1, respectively, the effluent was delivered as influent of an anaerobic ammonia oxidation reactor (ASBR). The effect of different HRTs (36 h, 33 h, 30 h, 27 h) on nitrogen removal of ANAMMOX and heterotrophic denitrification were investigated under conditions of temperature of 24℃ and pH of 7.2±0.2. Results showed that 1 nitrogen removal efficiency was optimum with HRT of 33 h. The average total nitrogen load rate(TNLR)and total nitrogen removal rate(TNRR)were 0.056 kg·(m3·d)-1and 0.050 kg·(m3·d)-1, respectively. The average effluent concentrations of NH4+-N, NO2--N, and COD were 1.36, 0.47, and 49.79 mg·L-1, and removal rates were 96.30%, 98.83%, and 56.17%, respectively. △NO2--N/△NH4+-N and △NO3--N/△NH4+-N were 1.17 and 0.15, 0.15 and 0.11 less than theoretical ANAMMOX values (1.32, 0.26) due to heterotrophic denitrification. 2 The contribution of ANAMMOX to nitrogen removal decreased; however, the contribution of heterotrophic denitrification to nitrogen removal gradually increased with decreasing HRT. This provides a point of reference for ANAMMOX in engineering applications.

Effect of Step Feed on Denitrifying Phosphorus and Nitrate Removal in a Modification of the Two Sludge A2/O-BAF System

A modification of the two sludge A2/O-BAF system was used to treat low C/N real domestic sewage. In order to improve the utilization of the carbon source, the effects of two step feeds (pre-anoxic zone and anoxic zone) on denitrifying phosphorus and nitrate removal were studied. According to the formula of material balance for COD, the utilization of carbon source was analyzed and evaluated under different ratios of step feed, simultaneously. The results showed that when the ratio of step feed was 7:3 and the influent concentrations of COD, NH4+-N, TN, and TP were 174.99, 58.19, 59.10, and 5.15 mg·L-1, respectively, their effluent concentrations were 29.48, 4.07, 14.10, and 0.40 mg·L-1, and the removal rates were 82.12%, 92.76%, 75.45%, and 91.20%, respectively. It was found that when the ratio of the denitrifying phosphorus accumulation organisms to the phosphorus accumulation organisms(DPAOs/PAOs) was 98.81%, the efficiencies of denitrifying phosphorus and nitrate removal were optimum. By optimizing step feed, the carbon source was utilized effectively, and the efficiencies of nitrogen and phosphorus removal were improved simultaneously. The theoretical basis has thus been provided for the modification of the two sludge A2/O-BAF system to treat low C/N waste water.

Effect of Aeration Rate on Shortcut Nitrification Recovery in Intermittent Aeration Mode

Shortcut nitrification sludge, which was set aside for two months, was recovered using Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ. The aeration rates of Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ were 120, 100, 80, and 60 L·h-1, respectively, while treating real domestic sewage, and the ratio of aerobic/anoxic was 30 min/30 min at the temperature of 25℃. The influent of ammonia was 50-80 mg·L-1, and the concentration of effluent ammonia was stable, at below 5 mg·L-1, after the 12th, 18th, 21st, and 21st cycles. The removal ratio of ammonia nitrogen was about 95%. The highest concentrations of nitrite for Reactors Ⅰ, Ⅱ, Ⅲ, and Ⅳ were 20.83, 22.81, 21.50, and 20.73 mg·L-1, respectively, which occurred in the 30th, 35th, 38th, and 42nd cycles, respectively. The concentrations of effluent nitrate were lower than 0.5 mg·L-1, and the nitrite accumulation rates were higher than 99%. The activity of ammonia-oxidizing bacteria (AOB) increased gradually and finally stabilized at 100.00%; however, the activity of nitrite-oxidizing bacteria (NOB) was gradually inhibited. The recovery of shortcut nitrification was achieved successfully in the different aeration modes.

Long-term stable simultaneous partial nitrification, anammox and denitrification (SNAD) process treating real domestic sewage using suspended activated sludge

Bottleneck issues such as difficult biofilm culturing, time-consuming granular formation and excessive nitrate production, always limited the application of anammox processes. By using the common but meaningful suspended activated sludge instead of biofilm or granule activated sludge, a combined anammox process, simultaneous partial nitrification, anammox and denitrification (SNAD), was established in a sequencing batch reactor (SBR) in this study to treat real domestic sewage and was operated for 300 days. Results indicated that a high ammonia removal rate and nitrogen removal rate (1.1 and 1.03 (kgN/(m3·d)), respectively) were achieved during the baseline phase treating high ammonia wastewater (350–550 mg/L). During the experimental phase treating domestic sewage with a C/N of 3–3.5, 86.1% of total nitrogen removal efficiency was achieved and only 1.02 mg/L of nitrate concentration was detected in the effluent with an averagely 64.6 mg/L of ammonium in the influent. Nitrogen mass balance analysis demonstrated that about 89% of total nitrogen (TN) was removed by anammox and the remaining 11% of TN was removed by denitrification. Bacterial abundance of Candidatus Brocadia and Thauera increased from 0.02% to 0.5% and 0.39% to 2.24% (from baseline phase to experimental phase), respectively, which made an essential contribution to the nitrogen removal. The advanced nitrogen removal performance reached in the SNAD process showed the possibility of using suspended sludge as a substitute of biofilm and granule sludge concerning anammox, and the process could treat real domestic sewage with a C/N of 3–3.5 without pretreatment of chemical oxygen demand (COD).

Effects of Temperature on Shortcut Nitrification and Nitrification Activity of Nitrification in an Intermittent Aeration Sequencing Batch Reactor

Real domestic sewage was treated with sequencing batch reactors (SBR). The aerobic/anoxic modes were alternated 4 times at 30℃ and 7 times at 18℃ in a single-cycle, respectively, and the ratio of aerobic/anoxic cycles was 30 min/30 min. The influent concentration of ammonia and nitrite was 61.44 mg·L-1 and 0.77 mg·L-1, respectively. After the experiments were run for 61 and 90 cycles, the effluent of the ammonia was 0.68 mg·L-1 and 1.28 mg·L-1 and the removal rate for ammonia was 98.94% and 99.57%, respectively. The nitrite concentrations were 20.57 mg·L-1 and 20.18 mg·L-1, and the nitrite accumulation rate reached 95.92% and 99.58%, respectively. During shortcut nitrification, the activity of the ammonia oxidizing bacteria (AOB) increased gradually before finally stabilizing at 100.00%, however the activity of nitrite oxidizing bacteria (NOB) increased first and then decreased gradually, the activity of AOB exceeded NOB at 32 and 74 cycles respectively, where the AOB became the dominant bacteria and the activity of NOB was completely inhibited at 61 and 90 cycles.

Quantitative characterization of organic diffusion using an analytical diffusion-reaction model and its application to assessing BOD removal when treating municipal wastewater in a plug flow reactor

The present study aimed to derive an analytical formula to quantify the diffusion of organic contaminant in a biofilm. The experiments were conducted to investigate the BOD degradation under the conditions of influent COD concentration from 50 to 300 mg/L, COD:N:P ratios of 100:5:1 and 100:15:3, with and without auxiliary aeration. The BOD removal rate was around 73% for non-aerated influent COD of 50 mg/L with 1-h hydraulic retention time. The BOD removal rate increased as the influent loading and hydraulic retention time increased while the influent COD was no more than 150 mg/L. Without aeration, the removal rate dropped significantly when influent COD increased to the range no less than 200 mg/L, due to the fact that the BOD diffusive flux driven by the biomass uptake was not further enhanced by higher ambient organic loading. The diffusion coefficient was calculated to be 1.12 × 10−6 m2/d with influent COD of 50 mg/L at COD:N:P ratio of 100:5:1 and 1 h hydraulic retention time and aeration, and the coefficient increased to 3.35 × 10−6 m2/d as the influent COD concentration increased to 300 mg/L. The diffusion coefficient decreased to 4.09 × 10−7 m2/d as the retention time increased to 3 h. The overall diffusion coefficients showed an increasing trend as the influent organic loading increased. The difference in diffusion coefficients between 1 and 2 h was apparently greater than that between 2 and 3 h, indicating a smaller overall diffusive flux due to a longer retention time. Further analysis revealed that BOD diffusion activity exhibited a declining trend as the wastewater travelled through the system. An analytical diffusion-reaction model was developed to characterize the diffusion behaviour, and applied to estimating the treatment efficiency for real domestic sewage. The result showed that the estimated effluent BOD concentrations were quite comparable to those from experimental measurements.

Pre treatment of Duckweed Biomass, Obtained from Wastewater Treatment Ponds, for Biogas Production

Considering the capacity of duckweed to treat wastewater and to produce valuable biomass, the present study aimed to highlight the potential of duckweed biomass harvested from wastewater treatment plant for biogas (methane) production. In this way a pilot system, comprising an anaerobic pretreatment and two duckweed ponds designed in series (10 m2 each), was operated with real domestic sewage. The treatment efficiency was evaluated through the monitoring of conventional physical–chemical water quality variables sach as Temperature, pH, total phosphorus (TP), phosphate (PO4), total nitrogen (TN), ammoniacal nitrogen (\(\text{NH}_{4}^{+}\)–N) and chemical oxygen demand (COD). Simultaneously the excess of biomass produced during the treatment was submitted to Biochemical Methane Potential test (BMP) carried out in a multi-batch reactor system. Three pretreatment approaches (fermentative, drying and alkaline) were performed in triplicate to evaluate their influence on methane production. Findings showed that the duckweed ponds removed the organic matter and nutrients from the wastewater (TN = 94%, TP = 92% and COD = 91%). Moreover, the biomass submitted to a fermentative pretreatment returned higher gas production (0.39 Nm³biogas/kgVSfed) compared with the anaerobic digestion (AD) of unpretreated biomass (0.25 Nm³biogas/kgVSfed). These results highlight the potential of duckweed ponds technologies to treat wastewater and produce clean energy simultaneously.

AN INNOVATIVE CONTINUOUS FLOW BNR-IC PROCESS FOR NUTRIENTS REMOVAL AND PHOSPHORUS RECOVERY FROM SYNTHETIC AND REAL DOMESTIC WASTEWATER

An innovative continuous flow process linking biological nutrients removal (BNR) with induced crystallization (IC) was used to remove nutrients and recover phosphorus (P) from synthetic and real domestic wastewater. The results showed that a good nutrients removal performance was found regardless of feeding solutions. P recovery efficiency from synthetic wastewater was 70.2% slightly less than that from real domestic sewage (74.2%). Importantly, P recovery can effectively enhance the subsequent biological P removal. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis displayed an obvious shift in microbial community structure when switching feeding synthetic solution to real wastewater. A total of 13 bands were detected in sludge samples using synthetic and real domestic sewage, affiliated with 8 phyla or classes domain Bacteria (Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Flavobacteria, Actinobacteria, Sphingobacteria, Epsilonproteobacteria and Chlorobia). The results obtained here suggest that the continuous flow BNR-IC process is feasible for nutrients removal and P recovery from domestic sewage and is a promising technology for wastewater treatment combined with recycling of P elements.

Optimization of Nitrogen Removal by Treating Real Domestic Sewage which is Low C/N in A/O Process

By treating real domestic sewage which is low C/N in A/O process ，results showed that different removal rates occured under different organic loadings、internal reflux ratio (R) without external carbon source . It was demonstrated that with the improvement of organic loading, F/M improved from 0.22kg/(kgMLSS•d) to 0.28kg/(kgMLSS•d), removal rates of TN and COD were improved by 4.84% and 16.55% respectively. Because lower C/N, TN and COD removal had no obvious enhancement by elevating R from 150% to 250% with organic loading is 0.28kg/(kgMLSS•d).

Cultivation and Performance of Aerobic Granules in a Pilot Scale SBR to Treat Real Domestic Sewage

Cultivation and Performance of Aerobic Granules in a Pilot Scale SBR to Treat Real Domestic Sewage

Determination effect of influent salinity and inhibition time on partial nitrification in a sequencing batch reactor treating saline sewage

With an increase in using seawater, saline sewage is necessarily disposed of to protect the ocean. The objective in this work is to evaluate the effect of influent salinity and inhibition time on short-cut nitrogen removal from real domestic saline sewage, and to detect the performance of nitrifiers in activated sludge in SBR. Microbial tests are used to establish the mechanism of salt inhibition. Dynamic response of salt is recorded during and after the salt inhibition stage. As microbial population tests support that NOB is strongly inhibited below 1% (w/v) salt content, three different salt levels (0.52%, 0.76% and 1.02%) are applied respectively in three parallel SBRs for 60 days. Results reveal that NARs all increase by 95% and keep steady after the 15th, 7th and 2nd day by adding salt. Ammonia is almost totally degraded at the steady state at salt levels below 0.75%; however, it degrades nearly half at 1.02%. After stopping salt addition, the ARE in a 1.02% system reaches 94.3% at the 18th cycle and the SAURs all apparently increase. The NAR in 0.52% and 0.76% systems decreases at the 9th and 20th cycle but still keeps above 95% in the 1.02% system. In order to gain steady shot-cut nitrification in a SBR, conditions of salinity greater than 0.76% and salt inhibition for more than 60 days are very competitive and favorable for application.