Treatment of pig manure liquid digestate in horizontal flow constructed wetlands: Effect of aeration

With the rapid development of scaled anaerobic digestion of pig manure, the generation of liquid anaerobic digestate exceeds the farmland loading capacity, causing serious environmental pollution. Three laboratory‐scale horizontal subsurface flow constructed wetlands (CWs; planted + aeration, planted, and unplanted) were set up to investigate the feasibility of liquid digestate treatment in wetlands. Treatment capacity in different wetlands was evaluated under different influent concentrations (chemical oxygen demand [COD], 5 days biochemical oxygen demand [BOD₅], and nitrogen forms). The effect of aeration and effluent recirculation on organic matter and total nitrogen removal was investigated. Results showed that integrating intermittent aeration in CWs significantly improved the oxygen condition (p < 0.01) in the wetland bed and promoted BOD₅ removal to 90% in aerated CWs as compared with <15% in the unaerated CWs. Meanwhile, COD removal between these three wetlands did not show any difference and varied from 52 to 72% under influent concentration of 200–820 mg/L because of the high content of hard‐degradable organic matter in the liquid digestate. Intermittent aeration resulted in high ammonium removal (>98%) although the influent loading varied from 65 to 350 mg/L. However, intermittent aeration caused nitrate accumulation of 300 mg/L and limited total nitrogen (TN) removal of 33%. To intensify the TN removal, we verified effluent recirculation to increase the removal efficiency of TN to 78%. These results not only show the potential application of CWs for treatment of high‐strength liquid anaerobic digested slurry, but also indicate the significance of intermittent aeration on the enhanced removal of organic matter and ammonium.     

Removal of pharmaceutical compounds in tropical constructed wetlands

The ability of tropical horizontal subsurface constructed wetlands (HSSF CWs) planted with Typha angustifolia to remove four widely used pharmaceutical compounds (carbamazepine, declofenac, ibuprofen and naproxen) at the relatively short hydraulic residence time of 2-4 days was documented. For both ibuprofen and naproxen, pharmaceutical compounds with low D_ow values, the planted beds showed significant (p < 0.05) enhancement of removal efficiencies (80% and 91%, respectively, at the 4 day HRT), compared to unplanted beds (60% and 52%, respectively). The presence of plants resulted in the removal of these pharmaceutical compounds from artificial wastewater. The more oxidizing environment in the rhizosphere might have played an important role, but other rhizosphere effects, beside rhizosphere aeration, appeared to be important also. Carbamazepine, considered one of the most recalcitrant pharmaceuticals, and declofenac showed low removal efficiencies in our CW, and this is attributable to their higher hydrophobicity. The fact that the removal of these compounds could be explained by the sorption onto the available organic surfaces, explains why there was no significant difference (p > 0.05) in their removal efficiencies between planted as compared to unplanted beds. No statistical significant differences (p > 0.05) were observed for the removal efficiencies of any of the pharmaceuticals tested for the 2-day HRT as compared to that corresponding to 4-day HRT. The rather efficient removal shown by the wetlands in this study (with HRTs of 2-4 days), indicates that such a CW system may be more practically used (with less land requirements) in tropical regions for removing conventional pollutants and certain pharmaceutical compounds from wastewater effluents.     

Removal of Pharmaceuticals and Personal Care Products during Water Recycling: Microbial Community Structure and Effects of Substrate Concentration

Many pharmaceuticals and personal care products (PPCPs) have been shown to be biotransformed in water treatment systems. However, little research exists on the effect of initial PPCP concentration on PPCP biotransformation or on the microbial communities treating impacted water. In this study, biological PPCP removal at various concentrations was assessed using laboratory columns inoculated with wastewater treatment plant effluent. Pyrosequencing was used to examine microbial communities in the columns and in soil from a soil aquifer treatment (SAT; a method of water treatment prior to reuse) site. Laboratory columns were supplied with different concentrations (0.25, 10, 100, or 1,000 μg liter⁻¹) of each of 15 PPCPs. Five PPCPs (4-isopropyl-3-methylphenol [biosol], p-chloro-m-xylenol, gemfibrozil, ketoprofen, and phenytoin) were not removed at any tested concentrations. Two PPCPs (naproxen and triclosan) exhibited removals independent of PPCP concentration. PPCP removal efficiencies were dependent on initial concentrations for biphenylol, p-chloro-m-cresol, chlorophene, diclofenac, 5-fluorouracil, ibuprofen, and valproic acid, showing that PPCP concentration can affect biotransformation. Biofilms from sand samples collected from the 0.25- and 10-μg liter⁻¹ PPCP columns were pyrosequenced along with SAT soil samples collected on three consecutive days of a wetting and drying cycle to enable comparison of these two communities exposed to PPCPs. SAT communities were similar to column communities in taxonomy and phylotype composition, and both were found to contain close relatives of known PPCP degraders. The efficiency of biological removal of PPCPs was found to be dependent on the concentration at which the contamination occurs for some, but not all, PPCPs.     

PPCPs removal by aerobic granular sludge membrane bioreactor

An aerobic granular sludge membrane bioreactor (GMBR) was applied to the treatment of pharmaceutical and personal care products (PPCPs) wastewater. The influence of granular sludge on five antibiotic and antiphlogistic PPCPs wastewater and the removal effect of methyl alcohol and conventional organic matter were investigated while constantly reducing the density of inflow organic matter. The results showed that the sludge granulation process in the system was rapid but unstable, and that the system exhibits a dissolution–reunion dynamic equilibrium. The reactor demonstrated varying removal effects of PPCPs on different objects. The use of a GMBR was more effective for the removal of prednisolone, naproxen, and ibuprofen; the first two drugs were lower the average removal rate of which reached 98.46 and 84.02 %, respectively; whereas the average removal rate of ibuprofen was 63.32 %. By contrast, the GMBR has an insignificant degradation effect on antibiotics such as amoxicillin, indicating that such antibiotic medicine is not easily degraded by microorganisms, which plays different roles in system operation. Because of the different chemical structures and characteristics of drugs that result in various degradation behavior. During the GMBR granulation process, the value of mixed liquor volatility suspended solids (MLVSS) gradually increases from 1.5 to 4.1 g/L during the GMBR granulation process, and the removal rate of COD_Cr reaches up to 87.98 %. After reducing the density of organic matter is reduced, the removal rates of NH₃-N and TP both reach more than 90 %, respectively. Moreover, the proposed technique is considerably effective in the removal of methanol.     

Impact of loads,season, and plant species on the performance of a tropical constructed wetland polishing effluent from sugar factory stabilization ponds

The effects of wastewater loading rates and two macrophyte species on treatment of sugar factory stabilization pond effluent were investigated in a pilot-scale free water surface constructed wetland (FWS CW) system in western Kenya. For 12 months, four CWs were operated at a hydraulic loading rate of 75 mm day⁻¹ and four at 225 mm day⁻¹. Half the CWs were planted with Cyperus papyrus and half with Echinochloa pyramidalis. Water samples were taken at the inlets and outlets and analyzed for TP, TDP, NH₄-N, and TSS. Mass removal rates of the selected water quality parameters were compared during three periods designated the short rain (period 1), dry (period 2), and long rain (period 3) seasons. There was a significant linear relationship between the mass removal rate of TP, NH₄-N, and TSS and the mass load, and season had a significant effect on the mass removal rate of TSS, NH₄-N, and TDP. Mass loading rates for TDP were about 78% of those for TP, whereas TDP comprised 78–99% of TP mass outflow rates, indicating a release of dissolved P within the CWs. The only significant difference between the two macrophyte species was associated with mass removal of NH₄-N, with more efficient removal in CWs planted with C. papyrus than those with E. pyramidalis. TP mass removal rates were 50–80% higher when a mean water loss for CWs 6–8 during periods 1 and 2 was assumed to represent evapotranspiration for all CWs in period 3 instead of pan evaporation data. This illustrated the importance of accurate estimations of evapotranspiration for pollutant mass removal rates in CWs in tropical climates.     

Rehabilitation by constructed wetlands of available wastewater treatment plant in Sakhnin

In rural areas, insufficient wastewater treatment often causes serious environmental problems, especially for human health. Due to this problem, new wastewater treatment plants (WWTP) should be constructed or upgraded. When considering economic and maintenance factors, constructed wetlands (CWs) are more desirable processes. The available WWTP located in the Northern Israeli town of Sakhnin was redesigned and upgraded. To rehabilitate the WWTP, six new CWs having different operating conditions were constructed as a pilot project. The most appropriate place of construction of the CWs was thought to be at the end of the WWTP. From the beginning of the system, inlet and outlet pollution parameters such as chemical oxygen demand (COD), ammonia (NH₄-N⁺), total suspended solids (TSS), and phosphorus (PO₄-P³⁻) were monitored in the CWs from August 2005 to February 2006. As a result the most appropriate CWs were found having Phragmites as plant and volcanic tufa as media material. The maximum removal efficiencies were 71.8% on COD, 92.9% on TSS, 63.8% on ammonia for CW5 tank. Adversely, phosphorus removal was not so high in CW5. Phosphorus removal was negligible in the study.     

Comparison of the performance of horizontal and vertical flow constructed wetland planted with Rhynchospora corymbosa

Treatment performance of horizontal flow (HF) and vertical flow (VF) constructed wetland planted with Rhynchospora corymbosa were compared. The average porosity of the CW beds were 0.55, hydraulic retention time (HRT) of 3?days, hydraulic loading rate (HLR) and Organic Loading rate were 0.058?m/day and 3.96 (g·BOD/m²·day), respectively with a volumetric flow rate of 0.14 m³/day. The pollutant concentration of graywater before and after its introduction to the CWs was measured using standard sampling and analyses methods. The mean removal efficiencies (RE) for HF and VF CWs were BOD, 35% and 35.4%; COD, 61.9% and 56.7%; TN, 87% and 92%; TP, 95% and 65%; TSS, 86% and 59.6%; pH, 8.8% and 12.8%, respectively. The graywater was highly contaminated in terms of nutrient and organic load. The mean values of the parameters tested for different CWs were significantly different (P?≤?0.05). This comparative study favored HF over VF Constructed wetland with HF found to be a viable alternative for graywater treatment for organics, nutrients and suspended solids removal. The result provided insight into the performance of CWs planted with R. corymbosa.     

Dynamic variations of microbial community structure in Myriophyllum aquaticum constructed wetlands in response to different NH4+-N concentrations

Constructed wetlands (CWs) have received increasing attentions for their N removal performances, especially regarding NH₄⁺-N. Different influent NH₄⁺-N concentration may influence N removal efficiency in practice, while the effects of different NH₄⁺-N concentrations on microorganisms removing N in CWs are poorly understood. In this study, surface flow CWs planted with Myriophyllum (M). aquaticum were established to investigate the influences of different NH₄⁺-N concentrations on the composition, structure, and interactions of microbial community. Our findings suggested 105 mg/L NH₄⁺-N CWs achieved highest N removal rate, removing 89.30 % NH₄⁺-N and 92.34 % TN from the influent. The results of real-time quantitative polymerase chain reactions (qPCR) indicated abundances of nitrifying genes (nxrA) and denitrifying genes (narG, nirS, nirK, and nosZ) were increased by increasing NH₄⁺-N concentrations, and the strongest effects were observed in narG (8-fold) and nosZ genes (11-fold). Different NH₄⁺-N concentrations was proved to alter composition and structure of microbial communities via high-throughput sequencing, e.g. denitrifiers including Brevendomonas.sp, Dokdonella.sp and Rhodococcus.sp were enriched obviously with increasing NH₄⁺-N concentrations. In addition, network showed interactions among microbial populations and positive interactions were dramatically shifted and enhanced by increasing NH₄⁺-N concentrations.     

Use of horizontal subsurface flow constructed wetlands to treat reverse osmosis concentrate of rolling wastewater

According to the characteristics of the reverse osmosis concentrate (ROC) generated from iron and steel company, we used three sets of parallel horizontal subsurface flow (HSF) constructed wetlands (CWs) with different plants and substrate layouts to treat the high-salinity wastewater. The plant growth and removal efficiencies under saline condition were evaluated. The evaluation was based entirely on routinely collected water quality data and the physical and chemical characteristics of the plants (Phragmites australis, Typha latifolia, Iris wilsonii, and Scirpus planiculmis). The principal parameters of concern in the effluent were chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP). The results showed that the CWs were able to remove COD, TN, and TP from ROC. S. planiculmis was not suitable for the treatment of high-saline wastewater. The sequence of metals accumulated in CW plants was K>Ca>Na>Mg>Zn>Cu. More than 70% of metals were accumulated in the aboveground of P. australis. The CW filled with gravel and manganese ore and planted with P. australis and T. latifolia had the best performance of pollutant removal, with average removal of 49.96%, 39.45%, and 72.01% for COD, TN, and TP, respectively. The effluent water quality met the regulation in China. These results suggested that HSF CW planted with P. australis and T. latifolia can be applied for ROC pollutants removal.     

Performance of laboratory-scale constructed wetlands coupled with micro-electric field for heavy metal-contaminating wastewater treatment

This study reports the performance of laboratory-scale constructed wetlands coupled with micro-electric field (CWMEF) planted cannas (Canna generalis) for heavy metal-contaminating wastewater treatment. The CWMEF had a better performance for heavy metal (HM) removal from wastewater than did the ordinary constructed wetlands (CWs). Owing to the stimulation of the suitable voltage and electrical exposure time, cannas may grew better and in fact assimilated more metallic ions in CWMEF than in CWs. The environmental conditions in CWMEF, such as the higher pH by electrolysis of water, the presence of aluminum ions by anodizing of aluminum, caused chemical precipitation, physical adsorption and flocculation of metallic ions.     

Enhancement of nitrogen removal in towery hybrid constructed wetland to treat domestic wastewater for small rural communities

Efforts to protect watercourses, especially sources of drinking water, particularly in rural areas, are now underway in China. Nitrogen present in wastewater, due to its role in eutrophication and potential toxicity to aquatic species, is a focus of primary concern. Constructed wetlands (CWs), a simpler, less costly treatment alternative, have been used to treat domestic wastewater for small communities. Although showing great promise for removing carbonaceous materials from wastewater, wetland systems have not been successful in removing nitrogen mainly due to lack of dissolved oxygen (DO). To enhance nitrogen removal, a novel CW configuration with three stages, towery hybrid constructed wetland (THCW), was designed. The first and third stages were rectangle subsurface horizontal flow CWs, and the second stage was a circular three-layer free-water flow CW. Increased DO by passive aeration of a tower type cascade overflow from the upper layer into the lower layer in the second stage of the wetland enhanced nitrification rates. Denitrification rates were also improved by additional organic matter supplied as a result of bypass influent directly into the second stage. Evergreen tree Pond Cypress (Taxodium ascendens), industrial plants Mat Rush (Schoenoplectus trigueter) and Wild Rice shoots (Zizania aquatica), ornamental floriferous plants Pygmy Waterlily (Nymphaea tetragona) and Narrow-leaved Cattail (Typha angustifolia) were planted in the wetland. The average percentage of removal was 89%, 85%, 83%, 83% and 64% for total suspended solid, chemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorus, respectively. There was no significant difference (p < 0.05) at low and high hydraulic loads (16 cm/d and 32 cm/d) for performance of THCW. Nitrifying and denitrifying bacteria as well as potential nitrification activity and potential denitrification rates measured have shown that nitrification–denitrification is the main mechanism for nitrogen removal in the wetland. THCW also provided additional aesthetic benefits.     

Impacts of vegetation and temperature on the treatment of domestic sewage in constructed wetlands incorporated with Ferric-Carbon micro-electrolysis material

Ferric-Carbon Micro-Electrolysis (Fe/C-M/E) material had been widely used for the pretreatment of wastewater. Therefore, we hypothesized that Fe/C-M/E material could enhance the treatment of domestic sewage when it was integrated into constructed wetlands (CWs). In this study, CWs integrated with Fe/C-M/E material were developed. Druing the experiment of effect of vegetation on the performance of CWs, percentages of NH₄⁺-N, NO₃^?-N, total nitrogen (TN), and Chemical Oxygen Demand (COD) removed in polyculture (W1) were up to 91.8%, 97.0%, 92.3%, and 85.4%, respectively, which were much higher than those in Lythrum salicaria monoculture (W2) and Canna indica monoculture (W3). In the experiment of temperature influences on the removal efficiency of CWs, temperature substantially influenced the performance of CWs. For example, NO₃^?-N removal percentages of W1, W2, and W3 at high temperature (25.5°C and 19.8°C) were relatively stable and greater than 85.4%. At 8.9°C, however, a sharp decline of NO₃^?-N removal percentage was observed in all CWs. Temperature also influenced the Chemical Oxygen Demand (COD) removal and soil microbial activity and biomass. Overall, the polyculture (Lythrum salicaria +Canna indica) showed the best performance during most of the operating time, at an average temperature ≥ 19.8°C, due to the functional complementarity between vegetation. All the CWs consistently achieved high removal efficiency (above 96%) for TP in all experiments, irrespective of vegetation types, phosphorous loadings, and temperatures. In conclusion, polyculture was an attractive solution for the treatment of domestic sewage during most of the operating time (average temperature ≥ 19.8°C). Furthermore, CWs with Fe/C-M/E material were ideally suitable for domestic sewage treatment, especially for TP removal.     

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.     

Overexpression of two cold-responsive ATAF-like NAC transcription factors from fine-stem stylo (<Emphasis Type="Italic">Stylosanthes guianensis</Emphasis> var. <Emphasis Type="Italic">intermedia</Emphasis>) enhances cold tolerance in tobacco plants

Tissue culture data is non-linear in nature. Decision tree algorithms stand out in revealing the non-linear interactions and relationships between the predictors and responses. Classification and regression tree (CART), chi squared automatic interaction detector (CHAID) and exhaustive CHAID are the common decision tree algorithms. These three models were employed to predict and optimize the effect of minor mineral nutrients on shoot cultures of Corylus avellana L. cultivars. H₃BO₃, CuSO₄·5H₂O, MnSO₄·H₂O, Na₂MoO₄·2H₂O and Zn(NO₃)₂·6H₂O were tested in a range of 0.5?×?to 4?×?Driver and Kuniyuki (DKW) medium within a RSM optimal design. NiSO₄·6H₂O was also an input within the design with varying levels of 0 to 6 µM. Shoot quality and length were affected by genotype, B and Mo amounts. Multiplication rate depended on genotype, B, Zn and Cu levels. Callus formation was affected by genotype and B. Leaf size depended on genotype, Zn and Mn concentrations. Cu was a significant predictor of leaf color and Ni slightly improved SPAD readings (chlorophyll content). CART in general outperformed CHAID and exhaustive CHAID in terms of the predictive performance. Both CHAID and exhaustive CHAID failed to generate a tree model for a leaf size response. The optimal minor nutrients for hazelnuts based on the predictions of the CART algorithm were suggested to be: B 2.3?×?DKW, Cu 0.5×, Mn 0.5×, 2?×?Mo and Zn 2×.     

NOB suppression and adaptation strategies in the partial nitrification–Anammox process for a poultry manure anaerobic digester

Poultry manure contains high levels of ammonia, which result in a suboptimal bioconversion to methane in anaerobic digesters (AD). A simultaneous process of nitrification, Anammox and denitrification (SNAD) in a continuous granular bubble column reactor to treat the anaerobically digested poultry manure was implemented. Thus, two strategies to achieve high efficiencies were proposed in this study: (1) ammonia overload to suppress nitrite oxidizing bacteria (NOB) and (2) gradual adaptation of the partial nitrification–Anammox (PN–A) biomass to organic matter. During the NOB-suppression stage, microbial and physical biomass characterizations were performed and the NOB abundance decreased from 31.3% to 3.3%. During the adaptation stage, with a nitrogen loading rate of 0.34 g L⁻¹ d⁻¹, a hydraulic retention time of 1.24 d and an influent COD/N ratio of 2.63 ± 0.02, a maximum ammonia and total nitrogen removal of 100% and 91.68% were achieved, respectively. The relative abundances of the aerobic and the anaerobic ammonia-oxidizing bacteria were greater than 35% and 40% respectively, during the study. These strategies provided useful design tools for the efficient removal of nitrogen species in the presence of organic matter.     

Identifying the determinant habitat characteristics influencing the spatial distribution of Ferula ovina (Boiss.) in semiarid rangelands of Iran using machine learning methods

Ferula ovina (Boiss.) is a valuable but vulnerable monocarpic perennial forb species from Apiaceae plant family whose habitat has been degraded over the years; hence identifying the factors controlling its distribution is important to assist range managers for the reclamation activities. The specific objective of this study was to investigate the quantitative relationships between soil properties, topographical features, climate factors and F. ovina distribution in a semiarid part of central Iran and to assess the relative importance of these factors in controlling its spatial variability. To discern these complex relationships, artificial neural networks (ANNs), support vector machines (SVMs), and decision tree CHAID algorithm were employed. Results from the ANN, SVM, and CHAID models indicated that the climate and topographic conditions should be considered more in explaining the variability in F. ovina occurrence and distribution. Factors such as slope, precipitation of warmest month, and minimum temperature of coldest month were identified by the ANN, SVM, and CHAID models as the determinant factors influencing the spatial distribution of F. ovina in central Iran, respectively. Furthermore, CHAID approach showed greater potential in predicting the F. ovina occurrence in the study area. This study provides a strong basis for identifying the most determinant habitat characteristics of F. ovina and other vulnerable or endangered plant species in semiarid rangelands of Iran; however, its general analytical framework could be applied to other parts of the world with similar challenges.     

Plants used in constructed wetlands with horizontal subsurface flow: a review

The presence of macrophytes is one of the most conspicuous features of wetlands and their presence distinguishes constructed wetlands from unplanted soil filters or lagoons. The macrophytes growing in constructed wetlands have several properties in relation to the treatment process that make them an essential component of the design. However, only several roles of macrophytes apply to constructed wetlands with horizontal subsurface flow (HF CWs). The plants used in HF CWs designed for wastewater treatment should therefore: (1) be tolerant of high organic and nutrient loadings, (2) have rich belowground organs (i.e. roots and rhizomes) in order to provide substrate for attached bacteria and oxygenation (even very limited) of areas adjacent to roots and rhizomes and (3) have high aboveground biomass for winter insulation in cold and temperate regions and for nutrient removal via harvesting. The comparison of treatment efficiency of vegetated HF CWs and unplanted filters is not unanimous but most studies have shown that systems with plants achieve higher treatment efficiency. The vegetation has mostly a positive effect, i.e. supports higher treatment efficiency, for organics and nutrients like nitrogen and phosphorus. By far the most frequently used plant around the globe is Phragmites australis (Common reed). Species of the genera Typha (latifolia, angustifolia, domingensis, orientalis and glauca) and Scirpus (e.g. lacustris, validus, californicus and acutus) spp. are other commonly used species. In many countries, and especially in the tropics and subtropics, local plants including ornamental species are used for HF CWs.     

Substrate effect on bacterial communities from constructed wetlands planted with Typha latifolia treating industrial wastewater

Constructed wetlands (CWs) have been recognized as being able to effectively treat wastewater from municipal and industrial sources. This study focused on the effect of different substrates and long-term operation of horizontal subsurface flow CWs treating tannery wastewater on the bacterial communities. The CWs were planted with Typha latifolia in three types of substrate: two units with different types of expanded clay aggregates and one unit with fine gravel. Another unit with expanded clay was left unvegetated. Changes in the bacterial community related to the type of substrate, different hydraulic loading rates and along CW operation were examined using denaturating gradient gel electrophoresis (DGGE). Bacterial enumeration was also performed and several bacterial isolates were retrieved from the CWs. Phylogenetic affiliations of those isolates were obtained on the basis of 16S rRNA gene sequences and revealed that they were closely related to the genera Bacillus (TM1S1, TM1R3, TNR1 and TAR1), Paracoccus (TM1R2), Pseudomonas (TM1R1) and Halomonas (TM1S2).The type of substrate and the presence of T. latifolia had a major effect on the species richness and the structure of bacterial communities as inferred by numerical analysis of DGGE profiles.     

Effect of hydraulic retention time on the treatment of secondary effluent in a subsurface flow constructed wetland

This study evaluates the potential of subsurface flow (SSF) constructed wetlands (CWs) for tertiary treatment of wastewater at four shorter HRTs (1–4 days). The CWs were planted with Typha angustata, which was observed in our earlier study to be more efficient than Phragmites karka and Scirpus littoralis. The CWs comprised four rectangular treatment cells (2.14 m × 0.76 m × 0.61 m) filled with layers of gravel of two different sizes (approximately 2.5 cm and 1.5 cm diameter) to a depth of 0.61 m. The inflow rates of the secondary effluent in the four cells were accordingly fixed at 300 L d^?1, 150 L d^?1, 100 L d^?1 and 75 L d^?1, respectively, for 1, 2, 3 and 4 days HRT. The hydraulic loads ranged between 59.05 mm d^?1 and 236.22 mm d^?1.The wastewater inflow into the CW system as well as the treated effluent were analyzed, using standard methods, at regular intervals for various forms of nitrogen (NH₄-N, NO₃-N and TKN), orthophosphate-P and organic matter (BOD and COD) concentrations over a period of five weeks after the development of a dense stand.The higher HRT of 4 days not only helped maximum removal of all the pollutants but also maintained the stability of the treatment efficiency throughout the monitoring period. For the nutrients (NH₄-N, NO₃-N and TKN), HRT played a more significant role in their removal than in case of organic matter (BOD₃ and COD). More than 90% of NO₃-N and TKN and 100% of NH₄-N were removed from the wastewater at 4 days HRT.At lower HRTs, the mass loading rate was higher with greater fluctuation. However mass reduction efficiency of the T. angustata CW for all forms of nitrogen was >80% with the HRTs of 2, 3 and 4 days.     

The Analysis of a Microbial Community in the UV/O3-Anaerobic/Aerobic Integrated Process for Petrochemical Nanofiltration Concentrate (NFC) Treatment by 454-Pyrosequencing

In this study, high-throughput pyrosequencing was applied on the analysis of the microbial community of activated sludge and biofilm in a lab-scale UV/O₃- anaerobic/aerobic (A/O) integrated process for the treatment of petrochemical nanofiltration concentrate (NFC) wastewater. NFC is a type of saline wastewater with low biodegradability. From the anaerobic activated sludge (Sample A) and aerobic biofilm (Sample O), 59,748 and 51,231 valid sequence reads were obtained, respectively. The dominant phylotypes related to the metabolism of organic compounds, polycyclic aromatic hydrocarbon (PAH) biodegradation, assimilation of carbon from benzene, and the biodegradation of nitrogenous organic compounds were detected as genus Clostridium, genera Pseudomonas and Stenotrophomonas, class Betaproteobacteria, and genus Hyphomicrobium. Furthermore, the nitrite-oxidising bacteria Nitrospira, nitrite-reducing and sulphate-oxidising bacteria (NR-SRB) Thioalkalivibrio were also detected. In the last twenty operational days, the total Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) removal efficiencies on average were 64.93% and 62.06%, respectively. The removal efficiencies of ammonia nitrogen and Total Nitrogen (TN) on average were 90.51% and 75.11% during the entire treatment process.