Sewage Plant Effluent Research Articles

Groundwater protection around Makkah sewage treatment plant using hydrological and transport models

Makkah is depicted environmentally by scarcity of rainfall, elevated temperatures, and increasing rates of evaporation. These ambience factors have driven the city to a reduction in the water balance. The main water resources in Makkah are renewable groundwater aquifers. Despite numerous studies concerned in the assessment of groundwater quality in Makkah, this paper presents the groundwater pollution remediation near Makkah sewage treatment plant. The methodology of this study depends on the simulation of four scenarios of groundwater remediation under the treated effluent of Makkah sewage plant. These scenarios are injection wells of clean water (with and without surface recharge of the effluent Makkah sewage plant), discharge wells for the contaminated aquifer, and slurry wall to constrict the spread of aquifer pollutants. The simulation is performed using the hydrological model (MODFLOW) and transport model in groundwater systems (MT3D). The results revealed that the case of discharge wells was the best one for cleaning the aquifer. In contrast, the worst case was the injection wells with surface recharge causing the pollution spread over the whole area. The case of using the slurry wall proved an efficient approach for controlling the pollution spread through the path of Makkah sewage plant effluent flow.

The influence of in situ purification system on pathogen in the river fed by the drainage of sewage plant.

An in situ integrated system, consisting of ecological floating islands (EFI), ecological riverbeds (ER), and ecological filter dams (EFD), was built in a ditch only receiving the effluent of sewage plant; the effect of in situ technologies on the distribution of aquatic pathogen was investigated. The results showed the aquatic pathogen decreased along the ditch. Specifically, the relative abundance of Legionella, Aeromonas, and Acinetobacter decreased from 0.032, 0.035, and 0.26 to 0.026%, 0.012%, and 0.08%, respectively. Sedimentation, filtration, and sorption (provided by plant roots and biofilms on substrates) were principal processes for the removal. The nitrogen removal bacteria to prevent the potential risk of eutrophication were also evaluated. The EFI and ER were the dominant sites for Nitrosomonas (34.96%, 32.84%) and Nitrospira (35.74%, 54.73%) enrichment, while EFI and EFD facilitated the enrichment of denitrification bacteria. Notably, the relative abundance of endogenous denitrifiers (DNB-en) (including Dechloromonas at 9.72%, Thermomonas at 0.58%, and Saccharibacteria at 2.55%) exceeded those of exogenous denitrifiers (DNB-ex) (Thauera at 0.20%, Staphylococcus at 0.005%, and Rhodobacter at 0.27%). This study demonstrated that the in situ integrated system was effective in reducing the abundance of pathogens in the drainage channel, and the deficiency of DNB-ex and carbon sources made nitrate removal difficult.

Study on mechanism of removal of sudden Tetracycline by compound modified biological sand filtration process

The removal of tetracycline from the sewage plant effluents through advanced treatment methods is key to controlling tetracycline levels in the water environment. In this study, modified quartz sands (QS) were used in a biological sand filter to remove tetracycline. The modified QS, with different surface characteristics, were prepared using glass etching technology combined with subsequent chemical modification methods, including hydroxylation treatment, metal ion modification, and amino modification. The adsorption efficiency of hydroxylated QS was higher than that of metal ion modified and amino modified QS, with adsorption efficiencies of 20.4331 mg/kg, 12.8736 mg/kg, and 10.1737 mg/kg, respectively. Results indicated that QS primarily reduce tetracycline through adsorption. Adsorption on ordinary QS fit the pseudo-first-order kinetic model, while adsorption on other modified QS and biofilm-coated QS fit the pseudo-second-order kinetics model. Biodegradation was identified as another mechanism for tetracycline reduction, which fit the zero-order kinetic model. Pseudomonas alcaligenes and unclassified Pseudomonas accounted for 96.6% of the total tetracycline-degrading bacteria. This study elucidates the effectiveness and mechanisms of five types of QS in treating tetracycline from sewage plant effluents. It provides a novel method for tetracycline reduction in real-world wastewater scenarios.

Co-doped Fe3O4/α-FeOOH for highly efficient peroxymonosulfate activation to degrade trimethoprim: Occurrence of hybrid non-radical and radical pathways

Trimethoprim (TMP), as a widely used chemotherapeutic antibiotic agent, has caused potential risks to the aquatic environment. In this study, magnetic Co-doped Fe3O4/α-FeOOH was fabricated by a facile one-step ageing method and used for activation of peroxymonosulfate (PMS) in TMP degradation. It was found that low catalyst (0.5 g/L) and PMS addition (0.2 mM) led to the high degradation efficiency of TMP (97.2%, kobs = 0.11211 min−1) over a wide range of pH. The oxidation of active radical (SO4·−) and non-radical singlet oxygen (1O2) co-acted on TMP degradation. Besides, PMS was activated through the cycles between Co(II)/Co(III) and Fe(II)/Fe(III). Fifteen degradation intermediates of TMP were identified by LC-MS, and three possible degradation pathways including hydroxylation, demethylation, and cleavage were proposed. The recovered catalysts exhibited high stability and reusability, maintaining 80% TMP removal efficiency with inappreciable metal leaching (0.012 mg/L of Co, 0.113 mg/L of Fe) after six cycles. Besides, the Co–Fe3O4/α-FeOOH/PMS system was highly tolerant to inorganic anions and actual water bodies (river water, lake water, tap water, and sewage plant effluent). Overall, this work provided a promising way to the potential application of Fe-based binary metal oxide for PMS activation.

Two-dimensional hydrophilic ZIF-L as a highly-selective adsorbent for rapid phosphate removal from wastewater

Recently zeolitic imidazolate framework-8 (ZIF-8) is considered as a promising adsorbent for phosphate removal, due to their huge surface area from high porosity and strong affinity of Zn (II) centers to PO43− ions. However, the three-dimensional structure and hydrophobicity of commonly micron-sized ZIF-8 material result in a low capacity and a slow kinetics for phosphate adsorption. To overcome these shortcomings, a two-dimensional hydrophilic leaf-like ZIF (ZIF-L) adsorbent was prepared by a simple precipitation method. These features of ZIF-L led to a rapid phosphate-adsorbed rate of 0.0376 g mg−1 min−1, but just 0.0050 g mg−1 min−1 for ZIF-8. Compared to many reported ZIF-8 materials (38.22–41.7 mg g−1), a larger phosphate adsorption capacity of 75.18 ± 2.65 mg g−1 for 2D ZIF-L was mainly benefitting from abundant Zn-OH defects to form Zn-O-P bond, high zeta positive potential to generate electrostatic attraction and hydrophilic surface to expose active sites. Moreover, about 100% of phosphate was selectively adsorbed by ZIF-L from the real influent (1.61 mg L−1) and effluent (0.12 mg L−1) of sewage plant. Such an excellent phosphate removal performance of ZIF-L adsorbent enables its practical application in wastewater treatment.

Design a project of sewage plant to make the cross-section water quality reach standard

According to regulations, the cross-section of Wangjiawopeng is regarded as a national control section of the Daling River. The water quality of the section must meet the surface water level III standard. According to the survey, the total phosphorus in the effluent from the sewage plant in Jianchang exceeds the standard is the main reason for the failure of the water quality. In order to make the cross-section water quality reaching standard, it is necessary to carry out the advanced treatment of phosphorus in the sewage plant. (1) The precipitation reaction of phosphorus and coagulant in sewage is strengthened by optimizing the type of coagulant, optimizing the dosage of coagulant, and selecting suitable coagulant aids. (2) The removal efficiency of phosphorus is improved by high-speed fiber filtration technology. (3) Phosphorus is removed by flocculation-sedimentation-high-speed fiber filtration technology. Experiments show that the SS in the sewage plant effluent is less than 5mg/L and filter effluent TP is less than 0.2mg/L. The process construction investment is estimated to be 3.9 million yuan, and the operating electricity cost is estimated to be 0.2 cents/m3. The process has the characteristics of reliable processing technology, stable operation, easy maintenance.

Occurrence, toxicity and ecological risk of Bisphenol A analogues in aquatic environment – A review

Bisphenol analogues (BPs) have been widely applied to industry as the substitutes for bisphenol A (BPA), which have been detected frequently in surface water, sediment, sewage and sludge. The presence of BPs in natural environment could pose risks to the aquatic ecosystem and human health. This study outlined the occurrence, toxicity of BPs in aquatic environment and manifested their potential ecological risk to the aquatic ecosystem throughout the world. As for occurrence, BPA was losing its dominance, while BPs were occupying a large part, especially for bisphenol S (BPS), bisphenol F (BPF) and bisphenol AF (BPAF). In some heavily polluted areas, BPs concentration reached µg/L in aquatic environment, which in the effluent of sewage plants was higher than that in the surface water. BPs content in sludge and sediment was more than that in the aqueous phase. All BPs other than BPS and Bisphenol P (BPP) had moderate toxicity. The current data supports that exposure to BPs may have adverse effects on dysfunction of endocrine system such as thyroid hormone concentration, enzyme activity, and even cell dysfunction, gene damage and chromosomal abnormalities. According to the risk quotient (RQ), BPF shows the highest ecological risk in China, Japan and South Korea, followed by BPA and BPS. The occurrence of bisphenols and their neurotoxicity on aquatic organisms merit further investigation.

Adsorptive removal of plasticizer (dimethyl phthalate) and antibiotic (sulfamethazine) from municipal wastewater by magnetic carbon nanotubes

In this study, the adsorptive removal of plasticizer (dimethyl phthalate, DMP) and antibiotic (sulfamethazine, SMT) from synthetic and municipal wastewater was studied using multi-wall carbon nanotubes (MWCNTs) and magnetic (Fe3O4) MWCNTs. The competition of SMT and DMP for the adsorptive sites was examined. The adsorption kinetics, isotherms, thermodynamics, as well as the effect of initial pH and competitive adsorption of DMP and SMT were determined. Results showed that both adsorption processes were endothermic, and the maximum adsorption capacity for DMP was calculated to be 196.85 mg g−1 (MWCNTs) and 136.99 mg g−1 (Fe3O4/MWCNTs) at 303 K according to the Langmuir model. The second-order kinetic model and the Freundlich isotherm model could fit the experimental data. In addition, there was a competitive relationship between SMT and DMP for the adsorptive sites of Fe3O4/MWCNTs and MWCNTs, and DMP had obvious competitive effect on the SMT adsorption by Fe3O4/MWCNTs, possibly due to the electrostatic interaction. The adsorption capacity for SMT or DMP decreased in the influent and effluent of municipal sewage plant than that in the deionized water and tap water. Both adsorbents were effective in removal of COD/TOC and targeted pollutants.

Advanced treatment of sewage plant effluent by horizontal subsurface flow constructed wetlands: effect of coupling with cellulosic carbon sources

Advanced treatment of sewage plant effluent by horizontal subsurface flow constructed wetlands: effect of coupling with cellulosic carbon sources

Establishment and efficiency analysis of a single-stage denitrifying phosphorus removal system treating secondary effluent

For advanced phosphorus and nitrogen removal, denitrifying phosphorus removal (DPR) was used to treat secondary effluent of sewage plants based on alternating anoxic/anaerobic process within single-stage biofilter. Under the hydraulic load of 3 m3/(m2·h), average removal rates of TP and TN in the system were 61.05% and 90.54%. 82.7% of the NO3–-N removal occurred in the upper of the packing layer. TP removal occurred in upper and lower of the packing layer, accounting for 42.02% and 57.98% of the total removal, respectively. Biomass and bioactivity decreased proportional to the height incensement of packing layer. Nitrogen and phosphorus removal rates increased with anaerobic time while decreased with hydraulic load. 16S rDNA sequencing results showed dominant DNPAOs in the system included Acinetobacter and Dechloromonas, while dominant denitrifying bacteria included Flavobacterium, Comamonadaceae, Hydrogenophaga, Thauera and Azospira. The study further provided an effective and feasible way for advanced wastewater treatment.

Elimination of bacterial contaminations by treatment of water with boron-doped diamond electrodes.

Boron-doped diamond electrodes can be used to generate reactive oxygen species directly at the electrode's surface. This property was used in this study for in-situ electrochemical oxidation to eliminate different bacteria, i.e. Escherichia coli, Pseudomonas fluorescens and Pseudomonas aeruginosa, as well as Bacillus subtilis spores from water samples. Application of low voltages in the rage from 4 to 10V and short incubation times in the range of minutes allowed a complete disinfection of water contaminated with enterobacteria and freshwater microbes including nosocomial pathogens as well as a significant reduction of spores. A pilot reactor was constructed, which allowed to decrease microbial contamination of sewage plant effluent drastically. Boron-doped diamond electrodes allow efficient reduction of bacterial contaminations in water samples.

The Physico-Chemical Quality of Effluents of Selected Sewage Treatment Plants Draining into River Rwizi, Mbarara Municipality, Uganda

As population increases in urban areas, the domestic and industrial activities increase resulting in an increase in the volumes of wastewater and anthropogenic pollution, hence posing a threat to public health and environment. This study assessed the physical chemical quality of two main sewage plant effluents discharging into River Rwizi. Effluent water samples were analyzed for dissolved oxygen, colour, turbidity, total suspended solid, total iron, phosphates, alkalinity, magnesium, calcium carbonate, temperature, pH, ammonium, electrical conductivity, chloride and nitrates. Parameters were analyzed following standard methods of APHA (1985). The values obtained were compared with EPA (2001), NWSC (2015) and NEMA (1999) standards for waste water. Results showed that the mean values most of the parameters tested were higher than the recommended EPA, NWSC and NEMA standards. The mean colour was 1627.67°C and 1414.33°C in Kakoba and Taso sewage effluents respectively compared to EPA (20-150), NWSC (500) and NEMA (300) standards (p > 0.05). The mean alkalinity was 1390.17 mg/l and 1308.33 mg/l for Kakoba and Taso respectively compared with EPA (400) and NWSC (800) standards. DO had a mean concentration of 68.27 mg/l and 63.03 mg/l in Taso and Kakoba respectively compared to EPA and NEMA standard of 5 mg/l. Mg was 243.29 mg/l and 246.49 mg/l in Kakoba and Taso sewage effluents respectively compared to NEMA standard for waste water of 100 mg/l (p > 0.05). The mean pH was 8.26 and 8.16 in Taso and Kakoba sewage effluents respectively compared to NWSC and NEMA standard of 6.0 - 8.0. Phosphate mean concentration levels were 32.2 mg/l and 27.11 mg/l for Taso and Kakoba respectively compared to standards of EPA (0.5 - 0.7 mg/l) and NEMA (10 mg/l). NO3 was 10 mg/l and 5.83 mg/l in Kakoba and Taso sewage effluents respectively compared to NWSC maximum permissible limit of 5 mg/l. The mean NH4 concentration was 385.33 mg/l (Kakoba) and 50.0 mg/l (Taso) compared to the EPA guideline range (0.2 - 4 mg/l). Chloride (Cl) had a mean of 833.33 mg/l in Kakoba compared to EPA (250 mg/l), NWSC and NEMA (500 mg/l) standards. Therefore the study recommends for effective treatment of waste effluents from Kakoba and Taso sewage treatment plants before recycling in order to avoid pollution of river Rwizi.

Nano-curcumin incorporated polyethersulfone membranes for enhanced anti-biofouling in treatment of sewage plant effluent

Biofouling is a severe problem in membrane systems which hampers their broad applications because it requires regular chemical cleaning, reduces membrane life, and also decreases product quality. In this study, nanocurcumin (CCM) was prepared by sonication-assisted wet-milling technique and then incorporated in polyethersulfone (PES) membrane to enhance the anti-biofouling property. TEM analysis of the curcumin showed that nanomaterials are spherical. FTIR studies confirmed that the presence of CCM nanomaterial in PES membrane. Zone inhibition studies revealed that PES/CCM nanocomposite membranes exhibited the better anti-biofouling propensity against Escherichia coli and Pseudomonas aeruginosa. Static adhesion studies also showed that PES/CCM nanocomposite membranes prevented the attachment and proliferation of E. coli cells. Also, PES/2 wt% CCM nanocomposite membrane had a high thermal degradation temperature of 575.62 °C and tensile strength of 1.87 MPa. Moreover, addition of CCM nanomaterial in casting solution altered the membrane morphology and hydrophilicity. Further, pure water flux was increased up to 64.48 L·m−2·h−1 for PES/2 wt% CCM nanocomposite membrane. Filtration of raw sewage treatment plant effluent was also carried out. The incorporation of curcumin in membranes was effectively improved the antifouling tendency without compromised affecting the chemical oxygen demand reduction. This study highlights the anti-biofouling potential of CCM incorporated PES nanocomposite membranes, which could be utilized for various filtration applications.

Occurrence of estrogenic endocrine disrupting chemicals concern in sewage plant effluent

The purpose of this study was to give a worldwide overview of the concentrations of typical estrogenic endocrine disrupting chemicals (EDCs) in the effluent of sewage plants and then compare the concentration distribution of the estrogenic EDCs in ten countries based on the survey data of the estrogenic EDCs research. The concentrations of three main categories (totally eight kinds) of estrogenic EDCs including steroidal estrogens (estrone (E1), estradiol (E2), estriol (E3) and 17α-ethynylestradiol (EE2)), phenolic compounds (nonylphenol (NP) and bisphenol A (BPA)) and phthalate esters (dibutyl phthalate (DBP) and dibutyl phthalate (2-ethylhexyl) phthalate (DEHP)) in the effluents of sewage plants reported in major international journals over the past decade were collected. The statistics showed that the concentration distributions of eight kinds of EDCs were in the range of ng·L−1 to μg·L−1. The concentrations of steroidal estrogens mainly ranged within 50.00 ng·L−1, and the median concentrations of E1, E2, E3 and EE2 were 11.00, 3.68, 4.90 and 1.00 ng·L−1, respectively. Phenolic compounds and phthalate esters were found at μg·L−1 level (some individual values were at the high level of 40.00 μg·L−1). The median concentrations of BPA, NP, DBP and DEHP were 0.06, 0.55, 0.07 and 0.88 μg·L−1, respectively. The concentrations of phenolic compounds and phthalate esters in the effluents were higher than that of steroids estrogens. The analysis of the concentration in various ten countries showed that steroids estrogens, phenolic compounds and phthalate esters in sewage plant effluents were detected with high concentration in Canada, Spain and China, respectively.

Determination of selected antibiotics in the Istanbul strait sediments by solid-phase extraction and high performance liquid chromatography

Surface sediments from 12 different locations of the Istanbul Strait and Marmara Sea, Turkey were analysed for five antibiotics belonging to two different groups of widely used pharmaceuticals, tetracyclines (TCs) and fluoroquinolones (FQs), by solid-phase extraction and high performance liquid chromatography. These two groups of antibiotics, mainly used to prevent or treat illness for humans as well as for animals, are frequently detected in the effluent of municipal sewage plants, in the aquatic environments and in soils after being spread by liquid manure. The results of analysis revealed that measured concentrations of individual antibiotics were significantly different depending on sampling location. Chlortetracycline (CTC) was not detected in any of the samples. High concentrations were mainly found in urbanized regions of the Strait. The concentrations of the two tetracyclines ranged from not detectable to 27.3 μg kg−1 in freeze-dried marine sediments. Comparable results were obtained for the two fluoroquinolones with concentration levels from 1.3 μg kg−1 up 34.1 μg kg−1. This study is the first attempt to show the contamination degree of the Istanbul Strait sediments by emerging contaminants. Particular concern should be given concerning their potential side effects caused by the frequent consumption of mussels and fishes captured in the Istanbul Strait.

High-performance liquid chromatography coupled to direct analysis in real time mass spectrometry: Investigations on gradient elution and influence of complex matrices on signal intensities

Direct analysis in real time (DART) time-of-flight mass spectrometry (TOF-MS) has been tested for its suitability as a detector for gradient elution HPLC. Thereby a strong dependency of signal intensity on the amount of organic solvent present in the eluent could be observed. Adding a make-up liquid (iso-propanol) post-column to the HPLC effluent greatly enhanced detection limits for early eluting compounds. Limits of detection achieved employing this approach were in the range of 7–27 μg L −1 for the parabene test mixture and 15–87 μg L −1 for the pharmaceuticals. In further investigations DART ionization was compared to several other widely used atmospheric pressure ionization methods with respect to signal suppression phenomena occurring in when samples with problematic matrices are analyzed. For this purpose extracts from environmental and waste water samples were selected as model matrices which were subsequently spiked with a set of six substances commonly present in personal care products as well as six pharmaceuticals at concentration levels between 100 μg L −1 and 500 μg L −1 corresponding to 100 ng L −1 and 500 ng L −1 respectively in the original sample. With ionization suppression of less than 11% for most analytes investigated, DART ionization showed similar to even somewhat superior behavior compared to atmospheric pressure chemical ionization (APCI) and atmospheric pressure photo ionization (APPI) for the Danube river water extract; for the more challenging matrix of the sewage plant effluent extract DART provided better results with ion suppression being less than 11% for 9 out of 12 analytes while values for APCI were lying between 20% and >90%. Electrospray ionization (ESI) was much more affected by suppression effects than DART with values between 26% and 80% for Danube river water; in combination with the sewage plant effluent matrix suppression >50% was observed for all analytes.

Treating surface water with low nutrients concentration by mixed substrates constructed wetlands

Constructed wetland (CW) has been widely applied in nutrients reduction for eutrophication control, especially in the advanced treatment of effluent of municipal sewage plants or the in-lake river treatment with high hydraulic loads and low nutrient concentrations. But in real application, it shows lower nutrient removal efficiency. The main reason is that traditional substrates, such as soil and gravel have low capacity for nitrogen and phosphorus removal. This study aims to enhance nutrients removal in constructed wetland systems by using series of substrates including calcium silicate hydrate (CSH), vermiculite and ceramsite which are all investigated individually in static experiment or mixed in batch and continuous flow experiments. The result showed that the efficiency of phosphorus removal by CSH could reach 97%, much higher than the other substrates. However, when it was applied in CW, the removal efficiency decreased. Although vermiculite showed the highest ammonia nitrogen removal efficiency of 65.91%, the ammonia nitrogen removal efficiency may have depended on the action of microorganism. High total nitrogen removal efficiency was obtained in continuous-flow mixed substrate CW. Under a hydraulic retention time (HRT) of 18h and hydraulic loading rate (HLR) of 0.496 m3/m3.d, average total nitrogen removal efficiency of above 91% was achieved, but the average phosphorus removal efficiency was around 65% and this needs to be improved further.

Removal of dissolved estrogen in sewage effluents by β-cyclodextrin polymer

Substances with estrogenic activity are found in effluents of municipal sewage plants and dairy farms. These effluents have the potential to induce feminization in male fish. In this study, cyclodextrin polymers (CDPs) that are insoluble in both polar and non-polar solvents were selected for the removal of dissolved estrogens in the effluent of a municipal sewage plant. The removal capacity of CDPs was high in the order of β-CDP ≥ γ-CDP ≫ α-CDP. The mechanism for adsorption of estrogens to β-CDP was not only due to a host–guest interaction as molecular recognition by β-cyclodextrin (β-CD), but also due to adsorption by the polymer matrix. β-CDP of 0.2% (w/v) removed 17β-estradiol (E2) of about 70% from 10 −11 mol/L, and more than 90% from ≥ 10 −10 mol/L. The removal ratios of E2 in the presence of cholesterols, which are contained at higher concentrations than estrogens in sewage effluents and are adsorptive competitor for β-CDP, were about 85% at a cholesterol/E2 molar ratio of 100 and > 90% at molar ratios of 0.1, 1, and 10. The effluent from a municipal sewage plant had estrogenic activity corresponding to 5.5 × 10 −11 molE2/L by yeast two-hybrid assay. The estrogens in the effluent were also removed > 90% by the β-CDP treatment. Therefore, β-CDP is able to remove dissolved estrogens over a wide range of concentrations in the presence of various contaminants such as wastewaters.

Effects of light and microbial activity on the degradation of two fluoroquinolone antibiotics in pond water and sediment

Enrofloxacin (ENR) and ciprofloxacin (CIP) are two fluoroquinolone (FQ) antibiotics widely used to treat diseases of human beings and cultured animals. These two FQs are usually detected in the effluent of municipal sewage plants and related aquatic environments. The purpose of this study was to understand the fates of ENR and CIP in aquaculture pond water and a sediment slurry in a laboratory-scale experiment. Effects of light and microbial activity on the degradation of these two FQs were investigated. Results indicated that natural irradiation plays a major role in the degradation of ENR and CIP in pond water and the sediment slurry. The 50 % dissipation times (DT50) with non-sterile treatment were 0.01 and 18.4 d for ENR, and 0.04 and 17.3 d for CIP in the water and sediment slurry, respectively. On the other hand, the degradation of ENR and CIP under dark conditions was slow or even hindered, and all of their DT50 values exceeded 100 d. These two FQs degraded faster in the sediment slurry than in pond water under dark conditions. Artificial ultraviolet (UV) and fluorescence light had similar effects on the degradation of ENR in the pond water and sediment slurry. Degradation of CIP was faster with UV than with fluorescence light treatment, while no such difference was found for ENR degradation. CIP was a degradation product of ENR under both light and dark conditions, and DT50 values for both compounds were shorter in the presence of light. The phenomenon of biodegradation was observed during degradation of CIP in the sediment slurry under natural light.

Evaluation of extremely shallow vertical subsurface flow constructed wetland for nutrient removal

Mesocosm-scale vertical subsurface flow constructed wetlands (SSF, 0.5 m length, 0.3 m width) with different reed-bed thickness, including standard SSF (SD, 0.6 m deep), shallow SSF (S, 0.3 m deep) and extremely shallow SSF (ES, 0.075 m deep) were set up at sewage treatment plant and their nutrient removal efficiencies from the sewage plant effluent were compared under three hydraulic loading rate (HLR) conditions of 0.15, 0.45 and 0.75 m(3) m(-2) d(-1). A very interesting characteristics was found for the extremely shallow SSF, in which a high nitrogen removal efficiency was obtained despite the effective hydraulic retention time was only 1/8 times as long as the standard SSF. The results of kinetic analysis confirmed that the high volumetric nitrogen removal efficiency observed in the extremely shallow SSF did not depend on high response against the water temperature but on much higher basic nitrogen removal activity compared with other SSF. The phosphorus removal depending on the adsorption to sand in the reed-bed filter was, however, the lowest in the extremely shallow SSF although the volumetric removal efficiency was much higher compared with other SSF. Results of morphological analysis of rhizosphere collected from respective reed-bed suggested that the extremely shallow SSF lead to a very high-density rhizosphere, resulting in a high basic nitrogen removal activity and volumetric phosphorus removal efficiency.