Influent COD Concentration Research Articles

Effects of Influent C/N Ratios on Denitrifying Phosphorus Removal Performance Based on ABR-MBR Combined Process

An ABR-MBR integrated reactor based on a combination of the anaerobic baffled reactor (ABR) with the microbial phase separation and membrane bioreactor (MBR) with high-effect entrapment was constructed and the circulation and interactivity of the combined process were examined by adding nitrate recycling and sludge reflux. By increasing the influent COD to adjust the COD/TN ratio, the influence of the mechanism on the denitrifying phosphorus removal performance under the condition of continuous-flow was investigated. The results showed that the average effluent concentration of soluble phosphorus under different influent C/N conditions were 0.22, 0.34, 0.39, 0.42, and 2.45 mg·L-1 and the low influent C/N ratio was beneficial to phosphate removal. When the influent C/N was 4.8-6.0, the average removal rates of COD, TN, and soluble PO43--P were more than 87%, 76%, and 93%. In addition, when the influent C/N ratio was 3.6-6.0, the removal of TN was proportional to the anoxic phosphorus uptake of ABR and conducive to the removal of TN after increasing the influent COD concentration. Higher C/N ratios of the influent improved the removal of TN at this stage. Finally, the C/N ratio of 6 was suggested to achieve the simultaneous removal of nitrogen and phosphorus.

Effect of Temperature on the Performance of an Up-flow Anaerobic Sludge Fixed Film (UASFF) Bioreactor Treating Palm Oil Mill Effluent (POME)

This study investigates the performance of anaerobic digestion of palm oil mill effluent (POME) in an up-flow anaerobic sludge fixed film (UASFF) bioreactor at four different temperatures (24, 38, 50 and 60 °C) under optimized operating conditions (feed flow rate (QF) of 1.5 L day and up-flow velocity (Vup) of 0.75 m/h). Influent COD concentration was 14150 mg/L. Six quality parameters viz. COD removal, methane yield, TSS removal, oil and grease removal, effluent volatile fatty acids (VFA) and pH were monitored as the process response. COD removal and methane yield of 92% and 0.325 CH4/g CODremoved day were achieved respectively in mesophilic temperature (38 °C) at HRT of 1.5 day. Higher values (94% COD removal and 0.331 CH4/g CODremoved day) were obtained under thermophilic condition (50 °C). A 94% oil and grease removal was achieved at a temperature of 50 °C while it was 85 and 65% at 38 and 24 °C, respectively. The granules structure and activity did not undergo any changes at temperature of 50 °C. An increase in temperature from 50 to 60 °C caused a detrimental effect on treatment efficiency as the methanogenic activity was relatively terminated within <6 days.

Optimizing sulfur-driven mixotrophic denitrification process: System performance and nitrous oxide emission

Nitrate contamination of groundwater has been recognized as a significant environmental problem world widely. Sulfur-driven mixotrophic denitrification has been demonstrated as a promising groundwater treatment process, which though plays an important role in nitrous oxide (N2O) emissions, significantly contributing to the overall carbon footprint of the system. However, the current process optimizations only focus on nitrate removal and excess sulfate control, with the N2O emission being ignored. In this work, an integrated mathematical model was proposed to evaluate the N2O emission as well as the excess sulfate production and carbon source utilization in sulfur-driven mixotrophic denitrification process. In this model, autotrophic and heterotrophic denitrifiers use their corresponding electron donors (sulfur and organic matter, respectively) to reduce nitrate to nitrogen gas, with each modeled as three-step denitrification (NO3− to N2 via NO2− and N2O) driven by sulfur or organic matter to describe all potential N2O accumulation steps. The developed model, employing model parameters previously reported in literature, was successfully validated using N2O and sulfate data from two mixotrophic denitrification systems with different initial conditions. Modeling results revealed substantial N2O accumulation due to the relatively low autotrophic N2O reduction activity as compared to heterotrophic N2O reduction activity, explaining the observation that higher carbon source addition resulted in lower N2O accumulation in sulfur-driven mixotrophic denitrifying system. Based on the validated model, optimizations of the overall system performance were carried out. Application of the model to simulate long-term operations of sulfur-driven mixotrophic denitrification process indicates that longer sludge retention time reduces N2O emission due to better retention of active biomass. High-level total nitrogen removal with significant N2O emission mitigation, appropriate excess sulfate control and maximized COD utilization can be achieved simultaneously through controlling the influent nitrate and COD concentrations.

Performance evaluation and microbial community dynamics in a novel AnMBR for treating antibiotic solvent wastewater

This study aims at evaluating the performance and microbial community dynamics of anaerobic membrane bioreactor (AnMBR) treating antibiotic solvent wastewater at improved influent quality period. The whole process was divided into five phases according to the influent COD concentration with a fluctuated volume loading rate (VLR) ranging from 3.9 to 12.7kgCOD/(m3·d). After 249days of operation, the average COD and THF removal efficiency were 93.6% and 98.7%, respectively. The accumulation of VFA, relatively low pH, decline of biogas production and methane content were discovered at higher VLR (>10kgCOD/(m3·d)). Methanomicrobiales are the major population throughout the whole running period. Methanosaetaceae showed a minor relative abundance compared both of them, while Methanobacteriales remained a minimum value. Results showed that the reactor performed an excellent pollutants removal effect because of the function of membranes even at high VLR conditions.

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.

Application of the activated sludge model to aerated lagoons

The different kinds of aerated lagoons, which exclude anaerobic pre-treatment ponds, are described and the design approach for aerated lagoons is explained. This hinges around ensuring that the 1st lagoon is suspension mixed and the second and any additional are facultative. Selection of the retention time for the 1st lagoon is important to ensure complete utilization of the influent biodegradable organics. Minimum retention times to achieve this at 14 degreesC and 22 degreesC were determined with the general activated sludge kinetic simulation model for (i) readily biodegradable soluble organics (BSO) only, (ii) slowly biodegradable particulate organics (BPO) only, (iii) real municipal wastewater (20% BSO and 80% BPO) and (iv) real municipal wastewater with 5% OHO active VSS mass seed. The minimum hydraulic retention times for these four cases are: at 14 degreesC 1.3, 3.0, 2.0 and 1.5 d, respectively, and at 22 degreesC 0.3, 2.0, 1.2 and 1.0 d, respectively. From a comparison of the simulation results with the steady-state model calculations, washout of OHOs takes place at about 75% of these retention times. Approximate equations to estimate the power requirements for aeration by mechanical surface aerators and mixing are given. These equations are combined with those of the steady-state activated sludge lagoon model for calculating the oxygen requirements and the aeration power density (W/m3) in each lagoon. With these equations, it is shown that influent COD concentration needs to be between an upper and lower limit band to ensure that the 1st lagoon is suspension mixed and the second lagoon is facultative. This COD concentration band decreases as the influent flow increases. The important conclusion arising from this is that if the aerated lagoon system is applied for small rural communities, where land for these large systems is likely to be available, then additional mixing energy above that for aeration will need to be provided to ensure that the 1st lagoon is suspension mixed - this additional aeration cost makes it unlikely that aerated lagoons will be applied for municipal wastewater treatment. Matching mixing and aeration power requirements for industrial organic wastewaters is easier because these usually are significantly stronger than municipal wastewaters.

Membrane Bioreactor (MBR) as Alternative to a Conventional Activated Sludge System Followed by Ultrafiltration (CAS-UF) for the Treatment of Fischer-Tropsch Reaction Water from Gas-to-Liquids Industries

The potential of a membrane bioreactor (MBR) system to treat Fischer-Tropsch (FT) reaction water from gas-to-liquids (GTL) industries was investigated and compared with the current treatment system: a conventional activated sludge system followed by an ultrafiltration (CAS-UF) unit. The MBR and the CAS-UF systems were inoculated with municipal activated sludge and operated in parallel for 645 days with four interruptions using synthetic FT reaction water. Both treatment systems achieved a removal efficiency of 98 ± 0.1% within 60 days after inoculation, the COD influent concentration was 1014 ± 15 mg L−1. This suggests that MBRs form a suitable alternative to CAS-UF systems for the treatment of FT reaction water from the GTL industries. Moreover, the total fouling rates (Ft) of the membranes used from day 349 till the end were assessed. The average Ft was 7.3 ± 1.0 1010 m−1 day−1 for CAS-UF membranes and 2.8 ± 00.7 1010 m−1 day−1 for MBR-MT membranes. This indicates that MBR systems for the treatment of FT reaction water from the gas-to-liquids industries are less prone to fouling than CAS-UF systems.

Concurrent hydrogen production and phosphorus recovery in dual chamber microbial electrolysis cell

Concurrent hydrogen (H2) production and phosphorus (P) recovery were investigated in dual chamber microbial electrolysis cells (MECs). The aim of the study was to explore and understand the influence of applied voltage and influent COD concentration on concurrent H2 production and P recovery in MEC. P was efficiently precipitated at the cathode chamber and the precipitated crystals were verified as struvite, using X-ray diffraction and scanning electron microscopy analysis. The maximum P precipitation efficiency achieved by the MEC was 95%, and the maximum H2 production rate was 0.28m3-H2/m3-d. Response surface methodology showed that applied voltage had a great influence on H2 production and P recovery, while influent COD concentration had a significant effect on P recovery only. The overall energy recovery in the MEC was low and ranged from 25±1 to 37±1.7%. These results confirmed MECs capability for concurrent H2 production and P recovery.

Impact of SRT on the efficiency and microbial community of sequential anaerobic and aerobic membrane bioreactors for the treatment of textile industry wastewater

The aim of this study is to evaluate the impact of SRT (infinite, 60 and 30days) on the treatment and filtration characteristics of sequential anaerobic sulfate-reducing and aerobic sulfide-oxidizing MBRs treating textile wastewater. The influent COD, dye and sulfate concentrations were kept constant at 2000, 200 and 1000mg/L, respectively. The decreased SRT caused substantial and partial decreases in COD oxidation and sulfate reduction, respectively, due to decrease of biomass concentration. Complete color removal was observed in the AnMBR and a slight increase in color was detected in the AeMBR. Sludge filterabilities were assessed with specific resistance to filtration, capillary suction time, and supernatant filterability tests. Compact and non-porous cake layer formed in the AnMBR. Metal-sulfide and Ca-P were detected in the cake layers of AnMBR and AeMBR, respectively, by SEM-EDS analyses. Desulfuromonas thiophila and Thioalkalivibrio sulfidiphilus were dominant sulfate-reducing and sulfide oxidizing bacteria in AnMBR and AeMBR, respectively.

Concentration of Nitrate in Main Anoxic Stage and PHA, TP Metabolism for Nitrogen and Phosphorus Removal in Single Sludge System with Continuous Flow

Based on test results and mass balance, PHA, TP metabolic regularity was revealed under different nitrate nitrogen concentrations in main anoxic stage [c(NO3)] for nitrogen and phosphorus removal in single sludge system with continuous flow, then the effectiveness of using c(NO3) as control parameter was proved from the perspective of the reaction mechanism. During experiment period, the influent COD, total nitrogen (TN), and total phosphorus (TP) concentrations were stabilized at (285.78±18.19), (58.13±3.79), and(7.14±0.51) mg·L-1, respectively. The experiment was carried out under the condition that the c(NO3) values were 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 mg·L-1 based on the feedback control structure using PLC automatic control system to control the nitrifying liquid flow with the water quality. The sludge load of COD was (0.253±0.071)kg·(kg·d)-1, the sludge load of TP in anaerobic stage was (0.006±0.001) kg·(kg·d)-1, the sludge load of TN in aerobic stage was (0.049±0.006) kg·(kg·d)-1, the hydraulic retention time (HRT) in bioreactor was 9h, the sludge recycle flow was 0.5, and the mixed liquor recycle was 1.0. The results showed that effect of c(NO3) value on PHA synthesis and storage rate in the ANS was conspicuous, and the percentage of PHA storage occupied 74% of COD removal when c(NO3) value was 2.5 mg·L-1.The impact of c(NO3) value on PHA degraded in the main anoxic stage was great, and the percentage of PHA degradation in the main anoxic stage occupied 55% of total PHA degradation when c(NO3) value was 2.5 mg·L-1. The phosphorus released in anaerobic stage changed along with increasing c(NO3), and the amount of phosphorus released obtained the maximum value 6.16 g·d-1 when c(NO3) value was 2.5 mg·L-1. In addition, under c(NO3) value of 2.5 mg·L-1, the amount of total phosphorus uptake and anoxic phosphorus uptake obtained the maximum values of 8.04 g·d-1 and 3.67 g·d-1, respectively. Then it was confirmed thatc(NO3) could serve as a run controlling parameter with the best value of 2.5 mg·L-1 from the perspective of PHA and TP metabolic mechanism.

Treatment of artificial secondary effluent for effective nitrogen removal using a combination of corncob carbon source and bamboo charcoal filter

Nitrogen from secondary effluents has endangered the aquatic environment and human health. A new experimental setup combining a corncob carbon source and bamboo charcoal filter (BCF) was used to effectively purify artificial sewage treatment plant tail water that had high nitrate and nitrogen content, and a low carbon to nitrogen (C/N) ratio. The nitrogen concentration in the reactor's effluent was below the limit of 15 mg/L when the influent COD concentration was 20 mg/L–60 mg/L, the influent NO3−-N concentration was 15 mg/L–30 mg/L, and the hydraulic retention time (HRT) was 1 h–4 h. The reactor's maximum volumetric load of total nitrogen was 0.585 kg/(m3 d). The COD and NO3−-N balances of the reactor indicated that 4.77 g corncob was required to remove 1 g NO3−-N and 2 g corncob was required to release 1 g COD.

Performance of submerged anaerobic membrane bioreactor for thermomechanical pulping wastewater treatment

A hollow fiber submerged anaerobic membrane bioreactor (SAnMBR) was operated for 160 days for thermo-mechanical pulping pressate treatment. A COD removal efficiency of 83±4% was achieved under all tested conditions, although the residual COD in permeate increased slightly with an increase in influent COD. The biogas yield slightly decreased with a higher feed concentration. The EPS production increased with an increase in organic loading rate. Membrane performance was affected by both the influent COD concentration and biogas sparging rate. The fouling layer samples were characterized using various analytical tools. The results suggest that it is feasible and attractive to treat thermomechanical pulping wastewater by a hollow fiber SAnMBR. Cake layer formation was the dominant mechanism of membrane fouling. An increase in biogas sparging rate actively mitigated the accumulation and deposition of sludge on/in membrane module, thus favored the enhancement of membrane flux and an efficient long-term operation.

Treatment of fish farm sludge supernatant by aerated filter beds and steel slag filters—effect of organic loading rate

The goal of our study was to develop an on-site cost-effective and extensive method for the treatment of supernatant of the sludge settling silo of fresh water fish farms. The main objectives of this study were 1) to determine the effect of the organic loading rate (OLR) on organic matter and nutrient removal efficiency of a pilot treatment system consisting of a series of aerated filter beds (AFBs) and electric arc furnace steel slag filters operated at different void hydraulic retention times (HRTV), 2) to validate the P-Hydroslag model as a design tool for slag filters and 3) to propose preliminary design options for fish farm sludge treatment. The 11.5 month experiment was divided into two phases: Phase 1 (P1) of 8.5 months with a low OLR to the AFBs of 0.015kg BOD5m−3 d−1, and Phase 2 (P2) of 3 months with a high OLR of 0.5kg BOD5m−3 d−1. The results showed that the OLR affected the organic matter mineralization and nitrification efficiency of AFBs. With a low OLR and an influent COD concentration of 320mgL−1, an average COD removal efficiency of 95% was observed while with a high OLR and an influent COD of 5400mgL−1, an average COD reduction of 65% was achieved. Due to the high OLR during P2, no nitrification took place probably due to the low availability of oxygen in the AFBs. The TP removal efficiency of the AFBs was 50% during P1 (influent of 5.2mgL−1), and 88% during P2 (influent of 110mgL−1). All SCs showed a high o-PO4 removal efficiency of >98% during P1 (average influent of 1.8mg P L−1, effluent of 0.04mg P L−1) and >85% during P2 (average influent of 8.7mg P L−1, effluent of 0.65mg P L−1) with a decrease in efficiency only observed over time in the SC that received the highest organic loading rate. It was concluded that with optimal loading rates, this compact biological and physicochemical semi-extensive treatment system offers a promising alternative to the high energy demand and maintenance treatment systems for organic matter and phosphorus removal, and that this treatment system could be applicable to other agro-environmental, municipal or residential effluents.

Long term operation of continuous-flow system with enhanced biological phosphorus removal granules at different COD loading

In this study, a continuous-flow system with enhanced biological phosphorus removal (EBPR) granules was operated at different COD concentrations (200, 300 and 400mgL−1) to investigate the effect of COD loading on this system. The results showed that when the COD concentration in influent was increased to 400mgL−1, the anaerobic COD removal efficiency and total phosphorus removal efficiency reduced obviously and the settling ability of granules deteriorated due to the proliferation of filamentous bacteria. Moreover, high COD loading inhibited the EPS secretion and destroyed the stability of granules. Results of high-through pyrosequencing indicated that filamentous bacteria had a competitive advantage over polyphosphate-accumulating organisms (PAOs) at high COD loading. The performance of system, settling ability of granules and proportion of PAOs gradually recovered to the initial level after the COD concentration was reduced to 200mgL−1 on day 81.

Treatment and desalination of domestic wastewater for water reuse in a four-chamber microbial desalination cell.

Microbial desalination cells (MDCs) have been studied for contaminant removal from wastewater and salinity reduction in saline water. However, in an MDC wastewater treatment and desalination occurs in different streams, and high salinity of the treated wastewater creates challenges for wastewater reuse. Herein, a single-stream MDC (SMDC) with four chambers was developed for simultaneous organic removal and desalination in the same synthetic wastewater. This SMDC could achieve a desalination rate of 12.2-31.5mgL(-1)h(-1) and remove more than 90% of the organics and 75% of NH4 (+)-N; the pH imbalance between the anode and cathode chambers was also reduced. Several strategies such as controlling catholyte pH, increasing influent COD concentration, adopting the batch mode, applying external voltage, and increasing the alkalinity of wastewater were investigated for improving the SMDC performance. Under a condition of 0.4V external voltage, anolyte pH adjustment, and a batch mode, the SMDC decreased the wastewater salinity from 1.45 to below 0.75mScm(-1), which met the salinity standard of wastewater for irrigation. Those results encourage further development of the SMDC technology for sustainable wastewater treatment and reuse.

A novel pilot-scale stacked microbial fuel cell for efficient electricity generation and wastewater treatment

A novel stacked microbial fuel cell (MFC) which had a total volume of 72 L with granular activated carbon (GAC) packed bed electrodes was constructed and verified to present remarkable power generation and COD removal performance due to its advantageous design of stack and electrode configuration. During the fed-batch operation period, a power density of 50.9 ± 1.7 W/m3 and a COD removal efficiency of 97% were achieved within 48 h. Because of the differences among MFC modules in the stack, reversal current occurred in parallel circuit connection with high external resistances (>100 Ω). This reversal current consequently reduced the electrochemical performance of some MFC modules and led to a lower power density in parallel circuit connection than that in independent circuit connection. While increasing the influent COD concentrations from 200 to 800 mg/L at hydraulic retention time of 1.25 h in continuous operation mode, the power density of stacked MFC increased from 25.6 ± 2.5 to 42.1 ± 1.2 W/m3 and the COD removal rates increased from 1.3 to 5.2 kg COD/(m3 d). This study demonstrated that this novel MFC stack configuration coupling with GAC packed bed electrode could be a feasible strategy to effectively scale up MFC systems.

Aerobic, Anaerobic Treatability and Biogas Production Potential of a Wastewater from a Biodiesel Industry

The purpose was to investigate the treatability of a wastewater from a biodiesel production industry under (1) aerobic conditions, using domestic activated sludge as inoculum; (2) anaerobic conditions, using sludge from an anaerobic domestic wastewater treatment digester; (3) utilization of wastewater for biogas production. The aerobic biodegradation batch tests were conducted in reactors with a working volume of 1.0 L, according to Zahn Wellens’s methodology proposed by the Organization for Economic Co-operation and Development. The anaerobic treatability was determined by the methodology proposed by Field et al. (4o Seminario de Depuracion anaerobia de aguas residuales, Valladolid Universidad, Secretariado de Publicaciones, Valladolid, 1988). Based on the results of anaerobic biodegradation, four new reactors with a working volume of 1.0 L were inoculated to evaluate the biogas production potential. The experiments showed that wastewater can be degraded under aerobic conditions with no lag-phase. COD maximum concentration of 780 mg L−1 could be metabolized aerobically. The anaerobic biodegradation only started after the adaptation phase (3 days). After 28 days, it was possible to achieve removal efficiencies above 90 % for the conditions applied in anaerobic tests. It was possible to obtain 114 mL of biogas for the highest influent COD concentration of 800 mg L−1 and F/M ratio = 0.25.

Industrial-scale biological treatment of Chinese nutgall processing wastewater by combined expanded granular sludge bed and bio-contact oxidation

The industrial-scale biological treatment of Chinese nutgall processing wastewater was conducted with a 200 m 3 expanded granular sludge bed reactor and a 900 m 3 bio-contact oxidation reactor. The temperature of the two reactors was controlled under mesophilic conditions (32 - 40˚C), through changing the proportion of the dilution water, which was composed of steam condensation water and residual circulating water. The effluent COD, gallic acid, chroma, total nitrogen, total phosphorus levels and pH of both the expanded granular sludge bed and bio-contact oxidation reactors were monitored. In addition, the redox potential in the expanded granular sludge bed was recorded. The total COD removal efficiency was 87.257% when the influent COD concentration was 14 251±3 148 mg/L, and the ratio of wastewater: dilution water was 1:5. The removal efficiencies of gallic acid, chroma, total nitrogen, and total phosphorus were 72.221%, 43.940%, 64.151% and 39.316%, respectively. The effluent pH increased in either the expanded granular sludge bed reactor or the bio-contact oxidation reactor during the operation. The redox potential in the expanded granular sludge bed varied between -367 mV and -435 mV. The results indicate that the combined process was suitable for treating Chinese nutgall processing wastewater.

Response of a tidal operated constructed wetland to sudden organic and ammonium loading changes in treating high strength artificial wastewater

The knowledge on the response of tidal-operated constructed wetlands (CWs) to suddenly changed influent characteristics, such as ammonium and organic matter concentrations, remains unclear. This study set up a pilot-scale tidal-operated CW and examined its response to various sudden organic matter and ammonium loading changes under constant hydraulic loading rate and retention time. Results showed an oxidative condition in the wetland bed with a high oxygen transfer rate induced by tidal operation. Effluent ammonium fluctuated from 0.5mg/L to 62mg/L when the ammonium pulse loadings were adopted, indicating the limited buffering capacity of tidal-operated CWs to influent ammonium pulse loadings because of the short contact time. No negative influence from influent COD pulse loadings to nitrification was observed, even when the influent COD concentration increased up to 1200mg/L. The average constant effluent COD concentrations of 47mg/L and high removal efficiencies of 93% under various pulse loadings (300–1200mg/L) strongly indicated the high buffering capacity of tidal-operated CWs to suddenly changed organic matter loadings as well as its high degradation capacity driven by the enhanced oxygen transfer rate of tidal operation.

New advanced treatment of biologically treated effluents from traditional Chinese medicine wastewater using the coupling process of O3/H2O2-BAF

The coupling process of O3/H2O2-biological aerated filter (BAF) was used to treat biologically treated effluents from traditional Chinese medicine wastewater. Under optimum conditions (i.e. 20 min of O3/H2O2 oxidation, a O3 dosage (50 mg/L), a 27.5% H2O2 dosage (85 mg/L), pH (7–9), a gas to liquid ratio (3), hydraulic retention of BAF 3 h, temperature (17–26 ℃)), the removal efficiencies for COD and color were 84.6–85.4% and 80.5–83.3%, respectively. The operational cost of the coupling process would be around 0.2198 $/m3, the operational cost of the O3/H2O2 oxidation stage were 0.2039 $/m3 and 0.7619 $/kg COD removed, respectively. Moreover based on the experiment conditions and equipment, the COD values at different BAF height was expressed as a function of influent COD concentration, lnCCi=−1.40QCi0.26H. The equation may be used to predict the COD removal efficiency at different influent COD values for refinement design of BAF. Finally under optimum conditions, ozone consumption in the O3/H2O2 oxidation was 0.20 kg O3/kg COD removed, the O3/H2O2 oxidation enhanced the wastewater biodegradability from 0.11 to about 0.56, and the inhibitory effect of the O3/H2O2 oxidation on microbial growth during subsequent biodegradation accounted for only 8%.