H Hydraulic Retention Time Research Articles

Effect of Hydraulic Retention Time on the Performance of a Compact Moving Bed Biofilm Reactor for Effluent Polishing of Treated Sewage

Treated effluent from a wastewater treatment plant can be further reused as a water resource for a water supply treatment plant. In this case, the treated sewage gathered in the study of the Class V National Water Quality Standard (NWQS) of Malaysia would be treated for use as a water resource for a water treatment plant. In a moving bed biofilm reactor (MBBR) with a 500-L working volume, organic pollutants, undesirable nutrients, and bacteria were removed without disinfectant. At 24-h hydraulic retention time (HRT), the maximum removal efficiency of 5-day biological oxygen demand, ammonia–nitrogen (NH3-N), and total phosphorus were 71%, 48%, and 12%, respectively. The biofilm thickness, which was captured using scanning electron microscopy, increased from 102.6 μm (24-h HRT) to 297.1 μm (2-h HRT). A metagenomic analysis using 16S rRNA showed an abundance of anaerobic bacteria, especially from the Proteobacteria phylum, which made up almost 53% of the total microbes. MBBR operated at 24-h HRT could improve effluent quality, as its characteristics fell into Class IIA of the NWQS of Malaysia, with the exception of the NH3-N content, which indicated that the effluent needed conventional treatment prior to being reused as potable water.

Assessment of Woodchip Bioreactor Characteristics and Their Influences on Joint Nitrate and Pesticide Removal

We constructed a bench-scale continuous-flow (8 L total volume, 4.3 L/day) woodchip bioreactor and operated the reactor under field-like conditions to evaluate joint pesticide and nitrate removal. The continuous-flow reactor achieved 83.5 ± 8% diuron removal and 61.6 ± 11.9% imidacloprid removal with a 24 h hydraulic retention time (HRT). We designed a sequencing-batch reactor configuration (8 L total volume) to evaluate the impact of an aerobic phase on denitrification and pesticide removal performance. The sequencing-batch reactor achieved 89.2 ± 8.8% nitrate removal with a hydraulic retention time (HRT) of 12 h, while the continuous-flow design achieved 55.6 ± 9.1% nitrate removal with a 12 h HRT. There was no significant difference between pesticide removal between sequencing-batch and continuous-flow reactor types (p = 0.655 and p = 0.316 for diuron and imidacloprid removal, respectively). Kinetic batch tests revealed sorption, not microbial degradation, as the main mechanism of removal for both diuron and imidacloprid under denitrifying conditions. Imidacloprid removal ranged from 440.4 to 532.0 ng/g-woodchip (dry mass) and diuron removal between 468.6 and 553.8 ng/g-woodchip (dry mass) over 24 h. The bench-scale evaluation of pesticide behavior in woodchip bioreactors highlights the need to improve microbial degradation in such best management practices for pesticide removal.

Hydraulic characteristics of integrated settler based biofilm reactor as onsite sanitation system

Abstract The present study identifies the hydraulic efficiency of a novel onsite sanitation system at variable hydraulic shock loading conditions. The system consisted of three chambers, each working as an up-flow anaerobic bioreactor, accommodated within a single unit. The hydraulic characteristics were identified with the help of residence time distribution (RTD) analysis by step feeding of lithium chloride (LiCl) solution into the system. The experiments were run at variable hydraulic loading conditions at different peak flow factors (PFF) of 1, 2, 4 and 6 while maintaining 24-h hydraulic retention time. As revealed in the RTD analysis, the biofilm reactor achieved a very good hydraulic efficiency that varied from 0.76 to 0.81 at PFF 1, 2 and 4. Although in the case of PFF6, it was comparatively low. It was noted that the dispersion number was always below 0.2 at variable hydraulic shock loading conditions under different PFFs, which indicated that the reactor behaved perfectly between mixed-flow and plug-flow reactor. The system was also able to achieve good pollutant removal efficiency for chemical oxygen demand (COD) and total suspended solids (TSS) under all PFFs, which was more than 68 and 75%, respectively.

One waste and two products: choosing the best operational temperature and hydraulic retention time to recover hydrogen or 1,3-propanediol from glycerol fermentation.

This study aimed to compare the production of hydrogen and 1,3-propanediol from crude glycerol (10g/L) in mesophilic (30°C) and thermophilic (55°C) anaerobic fluidized bed reactors, namely AFBR30°C and AFBR55°C, respectively, at hydraulic retention times (HRT) reduced from 8 to 1h. In AFBR30°C, the absence or low hydrogen yields can be attributed to the production of 1,3-propanediol (maximum of 651mmol/molglycerol), and the formation of caproic acid (maximum of 1097mg/L) at HRTs between 8 and 2h. In AFBR55°C, the hydrogen yield of 1.20molH2/molglycerolconsumed was observed at the HRT of 1h. The maximum yield of 1,3-propanediol in AFBR55°C was equal to 804mmol/molglycerol at the HRT of 6h and was concomitant with the production of hydrogen (0.87molH2/molglycerolconsumed) and butyric acid (1447mg/L).

Treatment and resource utilization of dairy liquid digestate by nitrification of biological aerated filter coupled with assimilation of Chlorella pyrenoidosa.

Ammonia inhibition is considered a key issue when using liquid digestate for microalgae cultivation. To study the effect of pretreatment with a biological aerated filter (BAF) on microalgae culture with dairy liquid digestate, nitrification characteristics of BAFs under different hydraulic retention time (HRT) and the growth characteristics of Chlorella pyrenoidosa in effluents of BAFs were investigated. Results showed that the BAFs can rapidly nitrify ammonia nitrogen and significantly improve the light transmittance of liquid digestate (the maximum promotion rate was ~260%), and the effect improved as the HRT increased. Pretreatment of liquid digestate with BAFs can eliminate ammonia inhibition for C. pyrenoidosa. Furthermore, lipid, crude protein, and higher heating value (HHV) output were also not affected by HRT. The similar removal of nitrate nitrogen in microalgae culture systems using effluents with 6-h and 12-h HRT (21.59% and 21.07%, respectively) were recorded. The results suggested that BAF coupled with microalgae culture is a novel option on the resource utilization of dairy liquid digestate.

Start-up of a trickling photobioreactor for the treatment of domestic wastewater.

A stand-alone trickling photobioreactor (TPBR) was seeded with activated sludge and microalgae to treat domestic wastewater. The TPBR was started-up at 12-h hydraulic retention time at room temperature with 12:12h light:dark cycle. The light was provided by blue LED strips. The reactor has a total volume of 30L and is divided into six segments. Each segment is 30cm long and has a diameter of 15cm. Each segment was packed with polyurethane foam sponge cubes (2.5×2.5×2.5cm3 ) with 40% occupancy. The chemical oxygen demand (COD), total organic carbon (TOC), total nitrogen (TN), and phosphorus (P) of domestic wastewater varied in the range of 164-256mg/L, 84.4-133.8mg/L, 34.2-55.6mg/L, and 24.7-39.3mg/L,respectively, during this period. The COD, TOC, TN, and P concentrations in the effluent after 45days of operation were 30.24±3.36mg/L, 7.69±0.09mg/L, 16.67±0.39mg/L, and 17.48±0.5mg/L, respectively. The chlorophyll-to-biofilm biomass ratio increased during the experimental period. The above results indicate that the algal-bacterial symbiotic relationship is beneficial for carbon and nutrient removal from domestic wastewater. PRACTITIONER POINTS: Trickling photobioreactor works on natural ventilation and has low power requirements and a small footprint. The porous sponge media helped in immobilizing and subsequent harvesting of biomass. The reactor conditions favored the growth of diatoms (brown algae) over green algae.

Natural pyrite improves nitrate removal in constructed wetlands and makes wetland a sink for phosphorus in cold climates

Pyrite, a natural ore was introduced into constructed wetlands (CWs) to intensify the denitrification and phosphorus deposition in cold climate conditions. Here, CWs with matrices of pyrite/volcanic rock ratios (m/m) of 0:1(CW–V), 1:10 (CW–P1), 1:5 (CW–P2), 1:1 (CW–P3) and 2:1 (CW–P4) were set up. Compared with the control group (CW–V), CW-P1-4 produced a gradual increase of nitrate-nitrogen (NO3−-N) and total nitrogen (TN) removal by 6.4–19.9% and 6.2–17.5%, respectively, under a 24 h-hydraulic retention time (HRT). Accordingly, the pyrite based autotrophic denitrification (PAD) contributed to 6.7–24.7% of the TN removal in CW-P1-4. For phosphate-phosphorus (PO43--P) and total phosphorus (TP) removal, CW-P3 and CW-P4 shared the highest efficiency, which was approximately 60% higher than that in CW-V. The main deposition form of phosphorus in CW-P1-4 was iron and aluminium bound phosphorus (Fe/Al–P), which accounted for 43.2–74.2%. By contrast, calcium and magnesium bound phosphorus (Ca/Mg–P) was the major form in CW-V. In addition, sequencing data implied that Simplicispira was the most abundant heterotrophic denitrifiers in CWs in cold climate. Thiobacillus, which is involved in PAD, was highly enriched only in the rhizosphere (6.9%) and matrix (7.3%) of CW with pyrite.

Effect of influent feeding pattern on municipal tailwater treatment during a sulfur-based denitrification constructed wetland

This work studied three parallel pilot-scale constructed wetlands based on sulfur-based autotrophic denitrification (SAD-CWs) with horizontal, vertical-horizontal and integrated vertical inflow for nitrogen removal of municipal tailwater. SAD system played the predominant role for nitrate removal and the integrated vertical inflow pattern was the most efficient pattern with 96.1% NO3–-N and 44.3% total phosphorus (TP) removal efficiency, respectively, at the condition of 3.5 h hydraulic retention time (HRT) and 18.5–23.5 °C. Although no great and serious change for microbial community structure was observed among these systems, the diversity in term of abundance of microbes and certain function species was observed. Proteobacteria, Ignavibacterae and Chloroflexi were the dominant phyla and accounted for over 59.1%, 7.5%, and 6.0% in SAD-CWs, respectively. Moreover, the richness and diversity of denitrifies in SAD-CWs with integrated vertical inflow were both higher than that in the other two reactors, especially sulfur autotrophic denitrifying bacteria.

Assessment of sludge reduction and microbial dynamics in an OSA process with short anaerobic retention time

Abstract This study operated for 160 days and evaluated sludge minimization using an oxic-settling-anaerobic (OSA) system fed with real wastewater. At first, a pilot-scale conventional activated sludge (CAS) system was used to perform conventional wastewater treatment over a course of 60 days. Next, the CAS system was coupled with a sludge holding tank (SHT) in the sludge recirculation line to employ the OSA system, using a short 12h-hydraulic retention time (HRT) over a course of 100 days. The observed sludge yield ( Y obs ) dropped from 0.33 (CAS) to 0.19 (OSA) kg TSS kg−1 COD, ensuring a reduction of 43% of sludge in the OSA system. Better wastewater treatment performance was achieved using the OSA system (BOD5: 87%, TKN: 92%, NH 4 + -N: 94%) when compared with the CAS system (BOD5: 76%, TKN: 74%, NH 4 + -N: 78%), considering the organic matter and nitrogen removal rates. Moreover, the enrichment of anaerobic and hydrolyzing communities in the SHT (mainly Pedobacter and Acidovorax) enhanced the COD and nitrogen hydrolysis, which therefore improved the autotrophic metabolism in the aeration tank.

Surfactant removal from wastewater using photo-cathode microbial fuel cell and laterite-based hybrid treatment system.

Sodium dodecyl sulfate (SDS) is a widely used anionic surfactant, which finds its way to the receiving water body due tothe incapability of conventional wastewater treatment systems to completely remove it. A hybrid treatment system consisting of upflow microbial fuel cell (MFC) with titanium dioxide (TiO2) as a photocathode catalyst was developed for treating synthetic wastewater spiked with SDS (10.00 ± 0.46mg L-1). Effluent from anodic chamber of MFC was passed through raw laterite soil filter followed by the photo-cathodic chamber with TiO2-coated cathode irradiated with theUV spectrum. This hybrid system was operated under varying hydraulic retention time (HRT) in anodic chamber of MFC. The SDS removal efficiency of more than 96% along with organic matter removal efficiency of more than 71% was obtained by this hybrid system at different HRTs. The MFC having cathode coated with TiO2 could generate a maximum power density of 0.73Wm-3 and 0.46Wm-3 at the HRT of 12h and 8h, respectively, showing the adverse effect of increased SDS loading rate on the electrical performance of MFC. This investigation highlighted the importance of HRT in anodic chamber of MFC and offered solution for effective removalof surfactant from wastewater.

Pilot-scale, on-site investigation of crushed recycled glass as tertiary filter media for municipal lagoon wastewater treatment

ABSTRACT Glass recycling is a process that faces many obstacles, especially in the closed-loop context. Waste glass separation and transportation can become quite expensive, turning glass collection for remanufacture unfeasible. For this reason, it is important that alternative markets for waste glass are sought. This study evaluated crushed recycled glass as tertiary media in subsurface pilot-scale filters for on-site municipal wastewater treatment, using control sand media filters. Filters were operated over 128 days at a 24-h hydraulic retention time, treating secondary lagoon effluent from the rural municipality of Dunnottar, Manitoba, Canada. Crushed recycled glass filters removed 92%, 90% and 45% of the total suspended solids (TSS), ammonium nitrogen (NH4 +–N) and chemical oxygen demand (COD), respectively. Total suspended solids were removed equally well in sand and crushed recycled glass filters (α = 0.05), whereas NH4 +–N and COD reductions were 10% and 21% greater in sand media, respectively. Both sand and crushed recycled glass filters failed to achieve phosphorus (P) discharge guidelines. This study shows that there is potential for crushed recycled glass in wastewater filtration, especially to achieve TSS, COD and NH4 +–N removal. Small communities served by waste stabilization ponds could benefit from glass media filters, as waste glass could be diverted from curbside collection and utilized locally to polish municipal lagoon effluent.

Effect of cathode material and charge loading on the nitrification performance and bacterial community in leachate treating Electro-MBRs

Electro-MBR technology, which combines an electrocoagulation process inside the mixed liquor of a membrane bioreactor, was studied for the treatment of a high-strength ammonia leachate (124 ± 4 mg NH4-N L−1). A lab-scale aerobic Electro-MBR was operated with a solid retention time of 45 days, hydraulic retention times of 24h and 12h, and charge loading ranging from 100 to 400 mAh L−1. At 400 mAh L−1, with a combination of a Ti/Pt cathode and a sacrificial iron anode, removal percentages for ammonia nitrogen, total organic carbon, and total phosphorus were 99.8%, 38%, and 99.0%, respectively. At 400 mAh L−1, the estimated ferric ion dosage was 325 mg Fe3+ L−1. Experiments conducted with different cathode materials showed that previously reported inhibition phenomena may result from a cathodic nitrate reduction into ammonia nitrogen. Conventional cathode materials, such as graphite, have electrochemical nitrate reduction rates of −0.03 mg NO3-N mAh−1. By comparison, when using Ti/Pt, the rate was −0.0045 mg NO3-N mAh−1(85% lower than graphite due to its low hydrogen overpotential). Charge loading tested in this study had no significant impact on both nitrification performance and microbial population diversity. However, the relative abundance of the mixed liquor’s Nitrosomonas increased from 4.8% to 8.2% when the charge loading increased from 0 to 400 mAh L−1. Results from this study are promising for future applications of the Ti/Pt - Iron Electro-MBR in various high-strength ammonia wastewater treatment applications.

Assessing the impact of hydraulic conditions and absence of pretreatment on the treatability of pesticide formulation plant wastewater in a moving bed biofilm reactor

This study examined the treatability of a wastewater composed by industrial pesticide formulation and sanitary wastewaters using a bench scale moving bed biofilm reactor (MBBR). Throughout 742 days and 7 operational phases, tests were performed for several experimental conditions, including: 3 and 6 h hydraulic retention time (HRT); variation of the industrial effluent proportion from 2 to 8% v/v; utilization of various lots of the pretreated pesticide effluent or its raw form. Distinct responses were obtained regarding removal of chemical oxygen demand (COD) (varying from 48 to 84 %) and ammoniacal nitrogen (varying from 36 to 95 %), whereas sludge production remained always low (average 0.18 kg/(m3.d)). Maximum specific removal rates obtained in batch trials showed that the pretreatment of the pesticide wastewater is truly beneficial for keeping higher biofilm activities and preventing nitrification inhibition. Nevertheless, even in the absence of pretreatment, the pesticide wastewater showed high biodegradability, corresponding to 65 % of soluble COD for the operational conditions. Overall, it was shown that the MBBR, at HRT of 6 h and media filling ratio of 50 %, is a viable alternative for the secondary treatment of highly polluted pesticide wastewater even in the absence of pretreatment while preserving a biofilm with good depuration capacity, diverse microfauna and volatile fraction consistently over 85 %.

Performance evaluation of two trickling filters removing LAS and caffeine from wastewater: Light reactor (algal-bacterial consortium) vs dark reactor (bacterial consortium)

Micropollutant removal efficiencies of two trickling filters – operated under light and dark conditions were studied and compared. Linear alkylbenzene sulphonate (LAS) and caffeine were selected as model micropollutants. Both lab-scale trickling-filter type reactors were packed with polyurethane foam sponge cubes (2 cm × 2 cm × 2 cm) with 40% occupancy. The trickling filter with the white color LED light was named as Light Reactor (LR), which was operated under light: dark cycle of 12:12 h with a quantum flux of 15 μmoles/m2/s. No light was provided in the other trickling filter, named Dark Reactor (DR). Synthetic wastewater containing glucose (250 mg/L), LAS (12 mg/L), and caffeine (0.05 mg/L) was fed to the reactors at a hydraulic retention time (HRT) of 12- and 8-h at 25 °C for 2 months. The C, N, and P removal at 12-h HRT were 85%, 15%, and 49%, respectively, in LR, the corresponding values in DR were 88%, 18%, and 43%. Similarly, at 8-h HRT 90%, 24%, and 37% was observed in LR and 84%, 19%, and 37% in DR. However, the LAS and caffeine removal decreased from 99 to 96% and 96 to 86% respectively in LR, and from 96 to 79% in DR with decreasing the HRT from 12 to 8-h. The number of LAS degraders in LR (5.5×104 CFU/sponge cube) was higher compared to DR (2.2×104 CFU/sponge cube) at 8-h HRT. The above results indicate that algal-bacterial symbiotic relationship in LR was beneficial for carbon and micropollutants removal from domestic wastewater.

PH control and microbial community analysis with HCl or CO2 addition in H2-based autotrophic denitrification

H2-based autotrophic denitrification is promising to remove nitrate from water or wastewater lacking organic carbon sources, and pH is one of its most important process parameters. HCl and CO2 addition are known as adequate pH control methods for practical purposes. However, because of H2, added CO2 may participate in microbial metabolisms and affect denitrification mechanisms. Here, a combined micro-electrolysis and autotrophic denitrification (CEAD) reactor, in which H2 is generated based on galvanic-cell reactions between zero-valent iron and carbon, was optimized and continuously operated for 233 days by adding HCl or CO2 to control pH in the range of 7.2–8.2. Microbial communities were compared between the two pH-control methods through high-throughput sequencing of 16S rRNA, nirS, and nirK genes. Under a low COD/N ratio of 0.5 in the influent (with ∼36 mgNO3-–N/L), when adding HCl, the total nitrogen (TN) removal efficiency reached 91.4% ± 0.9% with a 28-h hydraulic retention time (HRT). When adding CO2, the TN removal efficiency was improved to 96.5% ± 1.7% with 24-h HRT. Significant differences of 16S rRNA and nirS genes between the two pH-control stages indicated the variation of microbial communities and nirS-type denitrifiers. With HCl addition, Thiobacillus, unclassified Comamonadaceae, Arenimonas, Limnobacter, and Thermomonas, which were reported previously as likely autotrophic or heterotrophic denitrifiers, were most dominant in the biofilms. With CO2 addition, the biofilms became dominated by Anaerolineaceae and Methylocystaceae (related to organic carbon metabolism), Denitratisoma (likely heterotrophic denitrifier), and uncultured bacteria TK10 and AKYG587. The results suggest that the added CO2 not only contributed to pH control but also participated in microbial metabolisms. This study provides useful insights into microbial mechanisms and further optimization of H2-based autotrophic denitrification in water and wastewater treatment.

Influence of Carrier Filling Ratio on the Advanced Nitrogen Removal from Wastewater Treatment Plant Effluent by Denitrifying MBBR.

The filling ratio (FR) of a carrier has an influence on the pollutant removal of the aerobic moving bed biofilm reactor (MBBR). However, the effect of the polyethylene (PE) carrier FR on the performance and microbial characteristics of the denitrifying MBBR for the treatment of wastewater treatment plant (WWTP) effluent has not been extensively studied. A bench-scale denitrifying MBBR was set up and operated with PE carrier FRs of 20%, 30%, 40%, and 50% for the degradation of chemical oxygen demand (COD) and nitrogen from WWTP effluent at 12 h hydraulic retention time (HRT). The nitrate removal rates with FRs of 20%, 30%, 40%, and 50% were 94.3 ± 3.9%, 87.7 ± 7.3%, 89.7 ± 11.6%, and 94.6 ± 4.0%, and the corresponding denitrification rates (rNO3--N) were 8.0 ± 5.6, 11.3 ± 4.6, 11.6 ± 4.6, and 10.0 ± 4.9 mg NO3−-N/L/d, respectively. Nitrous oxide reductase (nosZ) gene-based terminal restriction fragment length polymorphism (T-RFLP) analysis illustrated that the highest functional diversity (Shannon’s diversity index, H′) of biofilm microbial community was obtained at 30% FR. The quantitative polymerase chain reaction (qPCR) results indicated that the abundance of nitrate reductase (narG) and nosZ genes at 30% FR was significantly higher than that at 20% FR, and no significant changes were observed at 40% and 50% FRs. Thus, 30% FR was recommended as the optimal carrier FR for the denitrifying MBBR.

Methane-based denitrification kinetics and syntrophy in a membrane biofilm reactor at low methane pressure

A methane-based membrane biofilm reactor (MBfR) was assessed for a tertiary nitrogen removal process in domestic wastewater treatment. To mitigate effluent dissolved methane concentrations, the MBfR was operated with a 20% methane mixing ratio and a low pressure of 0.003 atm. The nitrate concentration was reduced from 20 to 4 mg/L with a low methane concentration of 3.3 mg/L in the effluent at 4 h hydraulic retention time (HRT). An in situ dissolved oxygen sensor showed a concentration of 0.045 mg/L in the MBfR, demonstrating methane oxidation under hypoxic conditions. Both 16S rRNA gene sequencing and metagenomic analysis identified bacteria capable of oxidation of methane coupled to denitrification (Methylocystis), whereas other bacteria were implicated in either methane oxidation (Methylococcus) or nitrate reduction (Escherichia). Reduced genetic potential for nitrate reduction to nitrite at a shorter HRT coincided with a decreased efficiency of denitrification, suggesting rate limitation by this initial step of denitrification. Genes encoding nitrite reduction to dinitrogen were at similar relative abundance under both HRT conditions. Our results provide mechanistic evidence for microbial syntrophy between aerobic methanotrophs and denitrifiers in methane-fed MBfRs operated under varying HRTs, with important implications for novel biological nitrogen removal to dilute wastewater.

Assessment of pollutant removal processes and kinetic modelling in vertical flow constructed wetlands at elevated pollutant loading.

Constructed wetland (CW), an ecological wastewater treatment technology, is low cost and easily to operate. Vertical flow constructed wetland (VF-CW) systems have been used to treat various wastewaters across the world. The present work exhibits the detail study of five type's multi-layered vertically constructed wetlands operated at 24h hydraulic retention time under semi-continuous vertical flow mode. Except N-NO3-, all the pollutants were sufficient removal in iron scraps constructed wetland (ISs-CW). The highest average pollutant removal efficiency achieved in ISs-CW was 85.04%, 77.57%, 85.99%, 62.01% and 88.91% for N-NH4+, N-NO2+, total nitrogen, total phosphate and sulphate respectively. The present CWs planted with Eichhornia crassipes is a promising system for municipal wastewater treatment. The first-order kinetic modelling was best suited for the removal rate since it presents higher R2, rate constant (k) and B values.

Performance of Aerobic Granular Sludge in Treating Soy Sauce Wastewater at Different Hydraulic Retention Time

Aerobic granular sludge had shown its capability in treating soy sauce wastewater, but its reactor performance, granules properties and biokinetics in different hydraulic retention times (HRT) is still unknown. To ensure the reactor is performed in optimum condition, a judicially selection of HRT is important. The study was conducted in a high and slender column operated according to a sequential batch reactor (SBR) with a sequence of aerobic and anaerobic/anoxic reaction phases. Three different HRTs (8, 16, 24 h) and different anaerobic and aerobic reaction time were evaluated. In the study demonstrated the increase in HRT could reduce the organic loading rate (OLR) as well as biomass yield (Yobs, Y), endogenous decay rate (kd) and overall specific biomass growth rate (µoverall). It was observed a slight increase in the mixed liquor suspended solid (MLSS) and the granules mean size as the OLR decreased. Meanwhile, in the lowest HRT reactor, a narrow diameter range of aerobic granule from 3 to 100 µm was observed due to the development of small and dense granules. The HRT of 24h with aerobic and anaerobic/anoxic reaction time of 3.88 and 7.77h respectively is the SBR’s best performances due to the improvement of the aerobic granular physical properties.

Diatomite strengthen COD and ammonia removal from an micro-aerobic EGSB reactor treating coking wastewater

The performance of one-stage micro-aerobic MAEGSB (OMAEGSB) reactor and two-stage MAEGSB (TMAEGSB) reactor treating actual coking wastewater with and without supplement of diatomite were investigated. The investigation has demonstrated that the two-stage MAEGSB reactor system treating actual coking wastewater could keep high COD and NH3-N removal with supplement of diatomite. With only 24h hydraulic retention time (HRT) (12h for MAEGSB I and 12h for MAEGSB II ), when without diatomite supplement, the TMAEGSB reactor system could attain 72.6% COD average removal and 25.8% NH3-N average removal. However, with 6g•L−1•d−1 diatomite supplement, the TMAEGSB reactor system could keep 84.3% COD average removal and 78.8%-92.8% NH3-N average removal. Such high NH3-N removal efficiency of the TMEGSB was because of the high phenol and thiocyanate (SCN) removal in the MAEGSB I reactor (97.9% and 77.9%) and correspondingly the low influent phenol and SCN concentration for the MAEGSB II reactor (33.9 mg•L−1 and 10.4 mg•L−1). Diatomite supplement could ensure stable and highly efficient phenol and SCN removal in the MAEGSB I reactor. Using TMAEGSB reactor system with diatomite supplement was a simple and high effectively strategy for treatment of actual coking wastewater.