A new sponge tray bioreactor in primary treated sewage effluent treatment

The new attached growth sponge tray bioreactor (STB) was evaluated at different operating conditions for removing organics and nutrients from primary treated sewage effluent. This STB was also assessed when using as a pre-treatment prior to micro-filtration (MF) for reducing membrane fouling. At a short hydraulic retention time (HRT) of 40 min, the STB could remove up to 92% of DOC and 40-56% of T-N and T-P at an organic loading rate (OLR) of 2.4 kg COD/m³ sponge day. This OLR is the best for the STB as compared to the OLRs of 0.6, 1.2 and 3.6 kg COD/m³ sponge day. At 28 mL/min of flow velocity (FV), STB achieved the highest efficiencies with 92% of DOC, 87.4% of T-P, and 54.8% of T-N removal. Finally, at the optimal OLR and FV, the STB could remove almost 90% of organic and nutrient, significantly reduce membrane fouling with HRT of only 120 min.     

Evaluation of 2- and 3-stage combinations of vertical and horizontal flow constructed wetlands for treating greenhouse wastewater

The adsorption characteristics of various filter media and treatment efficiency of small pilot-scale constructed wetlands (CWs) were investigated in order to design optimum CWs for treating greenhouse wastewater. Calcite was the best filter medium for the adsorption of ammonium nitrogen and phosphorus under various temperature and pH conditions. However, removal efficiency of calcite for total nitrogen (T-N) removal was low due primarily to high nitrate levels. Thus, several hybrid CWs (containing calcite as filter media) consisting of combinations of vertical flow (VF) and horizontal flow (HF) beds were evaluated for improving efficiency for T-N removal. Both 2- and 3-stage combinations of the VF and HF beds were tested. The optimum hybrid CWs was demonstrated to be a 3-stage combination of horizontal flow (HF)–vertical flow (VF)–horizontal flow (HF), which provided suitable conditions for both nitrification and denitrification, which improved removal of T-N in wastewater containing nitrate. In the HF–VF–HF 3-stage hybrid CWs, the reduction in chemical oxygen demand (COD), T-N, and total phosphorus (T-P) in the effluent were 95.1, 68.4 and 94.3%, respectively. The removal of COD, T-N and T-P in 3-stage HF–VF–HF CWs was rapid in order of VF (second stage) ≫ HF (first stage) ≫ HF (third stage), VF (second stage) ≫ HF (third stage) > HF (first stage) and VF (second stage) ≫ HF (first stage) ≫ HF (third stage), respectively.     

Sequence optimization in a sequencing batch reactor for biological nutrient removal from domestic wastewater

The purpose of this work was to determine optimum sequence retention times for nutrient removal with low-cost using very short aeration time in an SBR treating domestic wastewater. During the study, four different CYCLEs were evaluated, with the highest removal efficiencies recorded for the CYCLE with fill, anaerobic, aerobic1, anoxic, aerobic2, settle, and decant sequences operated at retention times of 0.5, 2, 2, 1, 0.75, 1, and 0.5 h, respectively. For this CYCLE, the removal efficiencies of chemical oxygen demand (COD), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH₃–N), total phosphorus (TP), and ortho-phosphate (PO₄–P) were found, on average, to be 91, 78, 85, 87, and 83%, respectively. The optimum sequence retention time was determined via the analysis of variance (ANOVA) using the Matlab software (Mathworks Inc.). The data indicated that the total time of the aerobic sequences was shorter than those of previous studies for similar level of removal efficiencies in all parameters including N and P.     

Sequencing batch membrane biofilm reactor for simultaneous nitrogen and phosphorus removal: novel application of membrane-aerated biofilm

A sequencing batch membrane biofilm reactor (SBMBfR) was developed for simultaneous carbon, nitrogen, and phosphorus removal from wastewater. This reactor was composed of two functional parts: (1) a gas-permeable membrane on which a nitrifying biofilm formed and (2) a bulk solution in which bacteria, mainly denitrifying polyphosphate-accumulating organisms (DNPAOs), were suspended. The reactor was operated sequentially under anaerobic condition and then under membrane aeration condition in one cycle. During the anaerobic period, organic carbon was consumed by DNPAOs; this was accompanied by phosphate release. During the subsequent membrane aeration period, nitrifying bacteria utilized oxygen supplied directly to them from the inside of the membrane. Consequently, the nitrite and nitrate products diffused into the bulk solution, where they were used by DNPAOs as electron acceptors for phosphate uptake. In a long-term sequencing batch operation, the mean removal efficiencies of total organic carbon (TOC), total nitrogen (T-N), and total phosphorus (T-P) under steady-state condition were 99%, 96%, and 90%, respectively. In addition, fluorescence in situ hybridization (FISH) clearly demonstrated the difference in bacterial community structure between the membrane biofilm and the suspended sludge: ammonia-oxidizing bacteria belonging to the Nitrosomonas group were dominant in the region adjacent to the membrane throughout the operation, and the occupation ratio of the well-known polyphosphate-accumulating organism (PAO) Candidatus "Accumulibacter phosphates" in the suspended sludge gradually increased to a maximum of 37%.     

Treatment of sewage water from tourist areas by anaerobic fixed-bed reactor

A laboratory-scale anaerobic fixed-bed reactor, operating at ambient temperature (30 to 35°C), was used to treat sewage water from tourist areas in Cuba at hydraulic retention times (HRT) ranging from 4 to 72 h. The total chemical oxygen demand (T-COD), total biological oxygen demand (T-BOD) and total suspended solids removal varied between 30 and 80%, 40 and 95% and 25 and 80%, respectively. Total and faecal coliforms were reduced by 98.1 to 99.9% and by 99.0% to 99.9% respectively, despite the marked decrease in HRT from 72 to 4 h.     

利用漂浮植物修复系统栽培风车草、彩叶草和茉莉净化富营养化污水的研究

在盛装容积为100L富营养化生活污水的陶缸中放置泡沫塑料板作为浮体材料,并用有孔塑料小杯作为漂浮植物修复系统,在温室内种植风车草、彩叶草和茉莉进行植物净化试验。分别测定了污水中的总磷(T-P)、水溶性磷(S-P)、铵态氮(NH4^+-N)、硝态氮(NO3^--N)和总氮(T-N)在种植这3种植物过程中的含量变化情况。结果表明,这3种植物经28d生长之后,风车草和彩叶草生长良好,生物量大,其干重分别是初始种植时的285．8％和371．4％,而茉莉生长较差,生物量增加少。其干重只是初始种植时的125％．风车草、彩叶草和茉莉对污水中的总氮的去除率分别为68．0％、62．0％和45．0％,对硝态氮的去除率分别为98．0％、80．0％和92．0％,对总磷的去除率分别为78．0％、66．0％和55．0％,对CODCr的去除率分别为90．6％、90．5％和88．0％．风车草和彩叶草在飘浮植物修复系统栽培中具有良好的去污效果。     

Removal of H(2)S by Thiobacillus denitrificans immobilized on different matrices

Biological removal of high concentrations of H(2)S was studied using the immobilized Thiobacillus denitrificans with peat moss, wood chip, ceramic and granular activated carbon (GAC) separately. Experiments on the physical adsorption capacity of matrix, retention time and pressure drop were carried out; the ability of bioreactor to buffer shock loading and the removal efficiency with different packing materials were also investigated. Besides, the kinetics of single-stage biodesulfuration was analyzed. The results showed that GAC provided higher bacteria adsorption capacity, showed a more resistance to shock loading and allowed better operational control with respect to pressure drop than other inert carriers. When the retention time was changed from 30 to 100 s at an influent concentration of 100 mg/L of H(2)S, the removal efficiencies were above 98%; when the inlet concentration of H(2)S were changed from 110 to 120 mg/L, an average 96.8% removal efficiency was achieved during the long-term operation for GAC bioreactor. Next to GAC, wood chip was found to be a good packing material; however, peat moss and ceramic had limited effectiveness and their removal efficiencies were less of 90%. The kinetic analysis showed that the maximum removal rate and the half-saturation constant of the GAC bioreactor were 666.7 mg (H(2)S)/(L.d) and 20.8 mg/L, respectively.     

Control of COD/N ratio for nutrient removal in a modified membrane bioreactor (MBR) treating high strength wastewater

A modified membrane bioreactor (MBR) system has been developed to evaluate the efficiency of nutrient removal in treating synthetic high strength water. This study examined the effect of influent COD/N ratio on this system. Results showed that above 95.0% removal efficiencies of organic matter were achieved; indicating COD removal was irrespective of COD/N ratio. The average removal efficiencies of total nitrogen (TN) and phosphate (PO(4)(3-)-P) with a COD/N ratio of 9.3 were the highest at 90.6% and 90.5%, respectively. Furthermore, TN removal was primarily based on simultaneous nitrification and denitrification (SND) process occurred in the aerobic zone. Decreased COD/N ratios to 7.0 and 5.3, TN removal efficiencies in steady-states were 69.3% and 71.2%, respectively. Both aerobic SND and conventional biological nitrification/denitrification contributed to nitrogen removal and the latter played dominant effect. PO(4)(3-)-P-release and uptake process ceased in steady-states of COD/N 7.0 and 5.3, which decreased its removal efficiency significantly.     

The effects on operation conditions of sludge retention time and carbon/nitrogen ratio in an intermittently aerated membrane bioreactor (IAMBR)

An intermittently aerated membrane bioreactor (IAMBR) system has been developed to improve the efficiency of nutrient removal, and for the stable treatment of organic matter which is contained as suspended solid (SS) in the influent. The important operating factors of an intermittently aerated bioreactor (IABR) are sludge retention times (SRTs) and carbon/nitrogen (C/N) ratios. Because research on IAMBR is young, this paper explores the effect of SRTs and C/N ratios on these systems. For SRTs of 20, 25, 30, and 40 days, there was little difference in the removal of COD, T–N, and T–P. In comparing C/N ratios of 4.5, 7, and 10, the COD concentration in permeate with a C/N ratio of 10 was most stable, although the concentration of organic matter in the influent was high. The removal efficiencies of T–N and T–P in permeate with a C/N ratio of 10 were the highest at 92.9% and 88.9%, respectively. This implies that a C/N ratio above 10 should be maintained for a nutrient removal efficiency of approximately 90%.     

Performance of anaerobic baffled reactor (ABR) treating synthetic wastewater containing p-nitrophenol

In this study, the effect of increasing p-nitrophenol (PNP) concentrations on the performance of anaerobic baffled reactor (ABR) (chemical oxygen demand (COD), removals, volatile fatty acid (VFA), p-aminophenol (PAP) and methane gas productions) was investigated through 240 days. The PNP concentrations were raised to 700 from 10 mg/L corresponding to PNP loading rates of 0.97 and 67.9 g/m³ day. The PNP and COD removal efficiencies were 99 and 90% at PNP loading rates as high as 33.9 g/m³ day, respectively, through the acclimation of anaerobic granular sludge. After this loading rate, the removal efficiencies decreased to 79%. The COD removal efficiencies were high in compartment 1 (E = 78–93%) while a small amount of COD removal was achieved in compartments 2 and 3. The PNP removal efficiencies were approximately 90% in all PNP loading rates except for loading rate of 0.97 g/m³ day. The maximum PNP removal efficiency was measured as 99% at a loading rate of 8.32 g/m³ day. The optimum PNP loading rate for maximum COD, PNP removals and methane yield was 8.32 g/m³ day. The total, methane gas productions and methane percentages were approximately 2160–2400 mL/day and 950–1250 mL/day and 44–52% for the PNP loading rates varying between 4.36 and 33.9 g/m³ day, respectively. For PNP loading rates varying between 33.9 and 67.9 g/m³ day, the total, methane gas productions and methane percentages were approximately 2160 and 960 mL/day and 44%, respectively. The highest total volatile fatty acid (TVFA) concentrations were found in the first compartment with fluctuated values varied between 50 and 200 mg/L indicating the acidogenesis. p-Aminophenol was found as the main intermediate through anaerobic degradation of PNP which later was broken down to phenol and ammonia.     

Effect of influent nutrient ratios and hydraulic retention time (HRT) on simultaneous phosphorus and nitrogen removal in a two-sludge sequencing batch reactor process

A laboratory-scale anaerobic–anoxic/nitrification sequencing batch reactor (A₂N-SBR) fed with domestic wastewater was operated to examine the effect of varying ratios of influent COD/P, COD/TN and TN/P on the nutrient removal. With the increased COD/P, the phosphorus removals exhibited an upward trend. The influent TN/P ratios had a positive linear correlation with the phosphorus removal efficiencies, mainly because nitrates act as electron acceptors for the phosphorus uptake in the A₂N-SBR. Moreover, it was found that lower COD/TN ratio, e.g. 3.5, did not significantly weaken the phosphorus removal, though the nitrogen removal first decreased greatly. The optimal phosphorus and nitrogen removals of 94% and 91%, respectively were achieved with influent COD/P and COD/TN ratios of 19.9 and 9.9, respectively. Additionally, a real-time control strategy for A₂N-SBR can be undertaken based on some characteristic points of pH, redox potential (ORP) and dissolved oxygen (DO) profiles in order to obtain the optimum hydraulic retention time (HRT) and improve the operating reliability.     

Evaluation of an integrated sponge--granular activated carbon fluidized bed bioreactor for treating primary treated sewage effluent

An integrated fluidized bed bioreactor (iFBBR) was designed to incorporate an aerobic sponge FBBR (ASB-FBBR) into an anoxic granular activated carbon FBBR (GAC-FBBR). This iFBBR was operated with and without adding a new starch based flocculant (NSBF) to treat synthetic primary treated sewage effluent (PTSE). The NSBF contains starch based cationic flocculants and trace nutrients. The results indicate that the iFBBR with NSBF addition could remove more than 93% dissolved organic carbon (DOC), 61% total nitrogen (T-N) and 60% total phosphorus (T-P) at just a very short hydraulic retention time of 50 min. The optimum frequency of adding NSBF to the iFFBR is four times per day. As a pretreatment to microfiltration, the iFFBR could increase 5 L/m² h of critical flux thus reducing the membrane fouling. In addition, better microbial activity was also observed with high DO consumption (>66%) and specific oxygen uptake rate (>35 mg O₂/g VSS h).     

Feasibility study of biogas upgrading coupled with nutrient removal from anaerobic effluents using microalgae-based processes

The present research was conducted to simultaneously optimize biogas upgrading and carbon and nutrient removal from centrates in a 180-L high-rate algal pond interconnected to an external CO₂ absorption unit. Different biogas and centrate supply strategies were assessed to increase biomass lipid content. Results showed 99 % CO₂ removal efficiencies from simulated biogas at liquid recirculation rates in the absorption column of 9.9 m³ m^?2 h^?1, concomitant with nitrogen and phosphorus removal efficiencies of 100 and 82 %, respectively, using a 1:70 diluted centrate at a hydraulic retention time of 7 days. The lipid content of the harvested algal–bacterial biomass remained low (2.9–11.2 %) regardless of the operational conditions, with no particular trend over time. The good settling characteristics of the algal–bacterial flocs resulted in harvesting efficiencies over 95 %, which represents a cost-effective alternative for algal biomass reutilization compared to conventional physical–chemical techniques. Finally, high microalgae biodiversity was found regardless of the operational conditions.     

A tracer study for assessing the interactions between hydraulic retention time and transport processes in a wetland system for nutrient removal

In this study, a new-generation subsurface upflow wetland (SUW) system packed with the unique sorption media was introduced for nutrient removal. To explore the interface between hydraulic and environmental performance, a tracer study was carried out in concert with a transport model to collectively provide hydraulic retention time (7.1 days) and compelling evidence of pollutant fate and transport processes. Research findings indicate that our pollution-control media demonstrate smooth nutrient removal efficiencies across different sampling port locations given the appropriate size distribution conversant with the anticipated hydraulic patterns and layered structure among the sorption media components. The sizable capacity for nutrient removal in this bioprocess confirms that SUW is a promising substitute for an extension of traditional on-site wastewater treatment systems.     

Occurrence of Pathogenic Free‐Living Amoebae and Bacterial Indicators in a Constructed Wetland Treating Domestic Wastewater from a Single Household

Constructed wetlands are effective wastewater treatment systems because of their ability to remove large amounts of organic matter and pathogens. The goals of this study were to characterize the presence of pathogenic free‐living amoebae and bacterial indicators (total and fecal coliforms), and to ascertain the removal efficiencies of physical and chemical pollutants, in a constructed wetland treating domestic wastewater from a single household. Influent and effluent samples were collected monthly over a ten‐month period for biological, physical and chemical analyses. Thirty‐two species of free‐living amoebae were isolated from the system. The genus Acanthamoeba was the most frequently encountered (59 %) and was removed from the wastewater with the greatest efficiency (80 %). Removal of bacteria was low, the highest removal rates were found in August (4 logarithmic units) and January (3 logarithmic units). The average removal efficiencies of suspended solids, BOD₅ and ammoniacal nitrogen were 71.5 %, 50.6 % and 13.1 %, respectively. The relatively low removal efficiencies of the various bacteriological, physical and chemical parameters suggest that the hydraulic retention time was probably insufficient for optimal treatment to occur. The effluent quality was unacceptable for unrestricted irrigation of crops that are eaten uncooked.     

Assessing the feasibility of achieving biological nutrient removal from wastewater at an Irish food processing factory

In Ireland, wastewaters emanating from the food industry typically contain elevated levels of nitrogen and phosphorus before treatment. Two pilot scale studies were performed to determine the feasibility of achieving biological N and P removal on-site at a food ingredients plant. The wastewater treated by the pilot reactors was that which resulted from the day-to-day production in the full-scale food ingredients plant. Both reactors were of the anaerobic/anoxic/oxic (A/A/O) design, however the sizing of the zones was varied in this study. In the first pilot study, while treating a wastewater of the following strength: 1008 mg COD/l; 30.1 mg NH4-N/l and 26.7 mg P/l, removal efficiencies of 93%, 99% and 98% were obtained for COD, NH4-N and P, respectively. In the second study, while operating at reduced hydraulic retention times and lower recycle rates, the pilot plant treated a wastewater of the following strength: 1757 mg COD/l; 62 mg NH4-N/l and 57 mg P/l, with removal efficiencies of 94%, 97% and 75% obtained for COD, NH4-N and P, respectively. This work showed that biological nutrient removal could be successfully applied to treatment of food industry wastewaters.     

In situ removal of contaminated suspended solids from a pond by filtration

Suspended solids (SS) which have been discharged into ponds, lakes, and enclosed sea areas from shores and rivers absorb various substances such as heavy metals and nutrients. In this study, a small upward filtration system was developed to remove contaminated SS from the water. The system consisted of a main body with a flotation device, three pumps, two float sensors, solar panels and batteries. The filter medium consisted of a nonwoven geotextile with a thickness of 5 mm. The pilot experiment was carried out in Shimizu Utozaka pond in Japan. SS, chemical oxygen demand (COD) and total phosphorus (T-P) removal efficiencies of 88.5%, 56.5% and 64.2% were obtained, respectively. In addition, the estimation of pollutant removal was determined from the amount of removed SS. This calculation enables not only the design of filtration systems for future individual cases, but also quantitative evaluation for the effect of restoration.     

Effect of COD/N ratio and salinity on the performance of sequencing batch reactors

The effects of COD/N ratio (3-6) and salt concentration (0.5-2%) on organics and nitrogen removal efficiencies in three bench top sequencing batch reactors (SBRs) with synthetic wastewater and one SBR with fish market wastewater were investigated under different operating schedules. The solids retention time (SRT, 20-100 days) and aeration time (4-10h) was also varied to monitor the performance. For synthetic wastewater, chemical oxygen demand (COD) removal efficiencies were consistently greater than 95%, irrespective of changes in COD/N ratio, aeration time and salt concentrations. Increasing the salt concentrations decreased the nitrification efficiency, while high COD/N ratio's favored better nitrogen removal (>90%). The treatment of real saline wastewater ( approximately 3.2%) from a fish market showed high COD (>80%) and nitrogen (>40%) removal efficiencies despite high loading rate and COD/N fluctuations, which is due to the acclimatization of the biomass within the SBR.     

Effect of redox mediator, AQDS, on the decolourisation of a reactive azo dye containing triazine group in a thermophilic anaerobic EGSB reactor

The feasibility of thermophilic (55 °C) anaerobic treatment applied to colour removal of a triazine contained reactive azo dye was investigated in two 0.53 l expanded granular sludge blanket (EGSB) reactors in parallel at a hydraulic retention time (HRT) of 10 h. Generally, this group of azo dyes shows the lowest decolourisation rates during mesophilic anaerobic treatment. The impact of the redox mediator addition on colour removal rates was also evaluated. Reactive Red 2 (RR2) and anthraquinone-2,6-disulfonate (AQDS) were selected as model compounds for azo dye and redox mediator, respectively. The reactors achieved excellent colour removal efficiencies with a high stability, even when high loading rates of RR2 were applied (2.7 g RR2 l⁻¹ per day). Although AQDS addition at catalytic concentrations improved the decolourisation rates, the impact of AQDS on colour removal was less apparent than expected. Results show that the AQDS-free reactor R2 achieved excellent colour removal rates with efficiencies around 91%, compared with the efficiencies around 95% for the AQDS-supplied reactor R1. Batch experiments confirmed that the decolourisation rates were co-substrate dependent, in which the volatile fatty acids (VFA) mixture was the least efficient co-substrate. The highest decolourisation rate was achieved in the presence of either hydrogen or formate, although the presence of glucose had a significant impact on the colour removal rates.     

Effect of progesterone releasing intravaginal device (PRID) on fertility in the post-partum buffalo cow

Serum progesterone (P) profiles, following progesterone releasing intravaginal device (PRID) treatment (Experiment I) and use of the PRID for induction of fertile oestrus (Experiments II, III and IV), were studied in five non-cycling, buffalo heifers and 86 post-partum buffalo cows, respectively. The maximum P concentration (2.5 ng/ml) was attained 24 h after insertion of the device. Thereafter, P levels gradually decreased to 1 ng/ml at the time of removal of the device on day 12. In post-partum cows, the retention rate of the PRID was 100%, and more than 80% of the animals exhibited signs of oestrus after PRID removal. However, the conception rate following natural mating (26%) and fixed-time insemination (33%) at 60 and 84 h after PRID removal, was very low. Serum P levels and rectal palpation for active corpora lutea following PRID removal indicated a relatively high incidence of anovulatory oestrus post PRID treatment.