Unexpected difference in phenol sorption on PTMA- and BTMA-bentonite

The comparison of phenol sorption on phenyltrimethylammonium (PTMA)- and benzyltrimethylammonium (BTMA)-bentonite shows a clear difference as far as phenol sorption isotherms are concerned. For PTMA-bentonite the sorption isotherm is of a straight-line character which results from simple partitioning of phenol between the aqueous and organic phases sorbed on the bentonite surface. For BTMA-bentonite the isotherm has a convex shape, characteristic of physicochemical sorption.For the first time a three-parametric model, including the dissociation constant of phenol pK_a, distribution constant of phenol Kd_phen and phenolate anion Kd_phen⁻ between the aqueous phase and the bentonite phases is used for the evaluation of phenol sorption on organoclays with pH change. The model shows that the values of Kd_phen are higher than those of Kd_phen⁻ for all investigated initial phenol concentrations.The inspection of the FTIR spectrum of BTMA-bentonite loaded with phenol in the regions 1300–1600 and 1620–1680 cm⁻¹ shows the features of π–π electron interaction between the benzene rings of phenol and the BTMA cation together with the phenol–water hydrogen bond strengthened by this interaction.     

Factors affecting nitrate distribution in shallow groundwater under a beef farm in South Eastern Ireland

Groundwater contamination was characterised using a methodology which combines shallow groundwater geochemistry data from 17 piezometers over a 2 yr period in a statistical framework and hydrogeological techniques. Nitrate–N (NO₃-N) contaminant mass flux was calculated across three control planes (rows of piezometers) in six isolated plots. Results showed natural attenuation occurs on site although the method does not directly differentiate between dilution and denitrification. It was further investigated whether NO₃-N concentration in shallow groundwater (<5 m below ground level) generated from an agricultural point source on a 4.2 ha site on a beef farm in SE Ireland could be predicted from saturated hydraulic conductivity (K_sat) measurements, ground elevation (m Above Ordnance Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and distance from a dirty water point pollution source. Tobit regression, using a background concentration threshold of 2.6 mg NO₃-N L⁻¹ showed, when assessed individually in a step wise procedure, K_sat was significantly related to groundwater NO₃-N concentration. Distance of the point dirty water pollution source becomes significant when included with K_sat in the model. The model relationships show areas with higher K_sat values have less time for denitrification to occur, whereas lower K_sat values allow denitrification to occur. Areas with higher permeability transport greater NO₃-N fluxes to ground and surface waters. When the distribution of Cl⁻ was examined by the model, K_sat and ground elevation had the most explanatory power but K_sat was not significant pointing to dilution having an effect. Areas with low NO₃ concentration and unaffected Cl⁻ concentration points to denitrification, low NO₃ concentration and low Cl⁻ chloride concentration points to dilution and combining these findings allows areas of denitrification and dilution to be inferred. The effect of denitrification is further supported as mean groundwater NO₃-N was significantly (P < 0.05) related to groundwater N₂/Ar ratio, redox potential (Eh), dissolved O₂ and N₂ and was close to being significant with N₂O (P = 0.08). Calculating contaminant mass flux across more than one control plane is a useful tool to monitor natural attenuation. This tool allows the identification of hot spot areas where intervention other than natural attenuation may be needed to protect receptors.     

Composting of vinasse and cotton gin waste by using two different systems

Two composts were obtained by co-composting of a concentrated depotassified beet vinasse and cotton gin waste using two different aeration systems: static aerated pile (forced aeration provided by a blower whom operated in the positive mode) and windrow (turned pile). The composting mixtures were cotton gin trash (55%) and vinasse (45%) (dry weight). In static pile, the total amount of vinasse was added at the beginning of the process whereas, in windrow two additions of vinasse were performed. Differences in temperature changes between both composting systems were found: a faster increase of temperature in the windrow (54 °C at 7 days) than in the static pile (45 °C at 21 days) was observed. Probably in the static pile system, the compaction of the substrates made difficult the correct distribution of the air inside the pile. Moreover, after the second addition of vinasse a new thermophilic phase was started in windrow. The different aeration systems and the way of addition of vinasse could cause differences in organic matter (OM) degradation and in weight (22.6% for the static pile and 26.7% for the windrow) and gas losses during the process. Nevertheless, the composts obtained by the two systems had a high fertilizer value (25.1 g kg⁻¹ N; 3.2 g kg⁻¹ P₂O₅; 21.4 g kg⁻¹ K₂O; C/N8) for compost obtained in static pile and (16.2 g kg⁻¹ N; 3.4 g kg⁻¹ P₂O₅; 16.1 g kg⁻¹ K₂O; C/N 12) for compost obtained in the windrow). A high degree of stability was reached in the final composts. Composting of vinasse with cotton gin waste serves two objectives, disposal of wastes and recycling of waste components.     

The comparative study of the effects of 4 Hz Electromagnetic Fields-, Infrasound-treated and hydrogen peroxide containing physiological solutions on Na pump-induced inhibition of heart muscle contractility

The effects of 4 Hz extremely low frequency Electromagnetic Fields (ELF EMF), Infrasound (IS) and hydrogen peroxide (H₂O₂) on Na⁺–K⁺ pump-induced transient inhibition of heart muscle contractility was studied. It was documented that EMF-treated and H₂O₂-containing physiological solution had synergic depressing effect on Na⁺–K⁺ pump-induced inhibition of muscle contractility, while the IS had elevation effect on it. On the basis of the obtained data the H₂O₂ could be suggested as the messenger through which the stimulation effect of EMF on heart muscle is realised, while the relaxing effect of IS on heart contractility is due to the decrease of CO₂ solubility of muscle bathing aqueous medium.     

The convective hot air drying of Lactuca sativa slices

The storage of fresh agricultural products is not easy because of its high moisture. Dehydration is an efficient preservation method. The investigation of drying modeling and transfer characteristics are important for selecting operating conditions and equipment design. The drying behavior of Lactuca sativa slices, with the thickness of 2 mm, was investigated at 60.0–80.0°C and 0.60–1.04 m sec^?1 velocity in a convective hot air drier. The mass transfer during the drying process was described using six thin drying models. The convective heat transfer coefficient α and mass transfer coefficient k_H were finally calculated. The results showed that the drying process could be separated into three stages including accelerating rate, constant rate, and falling rate period, which was influenced by hot air temperature and velocity, and the Modi?ed Page model agreed well with the experimental data. When the operating temperature was increased from 60.0°C to 80.0°C, α was found increased from 88.07 to 107.93 W·m^?2·K^?1, and k_H increased from 46.32 × 10^–3 to 68.04 × 10^–3 kg·m^?2·sec^?1·ΔH^?1. With the increase of air velocity from 0.60 to 1.04 m·sec^?1, α was increased from 78.85 to 101.35 W·m^?2·K^?1, and k_H was enhanced from 51.78 × 10^–3 to 65.85 × 10^–3 kg·m^?2·sec^?1·ΔH^?1.     

Determination of dissolved oxygen limitation in aerobic biofilm reactors

The concentration of dissolved oxygen (DO) strongly influences the performance of aerobic biofilm reactors because organic oxidation is limited by the availability of oxygen. However, it is not necessary to maintain a high DO level in the reactors in order to overcome this limitation. Excessive aeration wastes energy. Therefore, the determination of the onset of DO limitation against organic substrate removal in aerobic biofilm reactors is important for their effective operation. This study is aimed at developing an expression to determine the onset of DO limitation and hence to control the aeration system. The expression developed is as follows: , where S_b and C_b are the bulk concentrations of organic substrate and DO, respectively; D_ws and D_wc are the diffusion coefficients of organic substrate and oxygen in the reactors respectively; and R_b is an overall ratio of oxygen consumption to organic substrate removal in the reactors. The latter is the key parameter in the equation, and is determined by the characteristics of the substrate, biofilm, and reactor. In order to measure the value of R_b, the authors have developed a micro-biofilm reactor. The value of R_b was determined to be 0.13 (mg O₂ mg⁻¹ COD_cr) for glucose removal with this reactor. The equation has, subsequently, been verified with data from batch and continuous experiments.     

Relationship between liquid depth and the acoustic generation of hydrogen: design aspect for large cavitational reactors with special focus on the role of the wave attenuation

Understanding the effect of the liquid depth (z) on the acoustic generation of hydrogen is highly required for designing large-scale sonoreactors for hydrogen production because acoustic cavitation is the central event that initiates sonochemical reactions. In this paper, we present a computational analysis of the liquid-depth effect on the generation of H₂ from a reactive acoustic bubble trapped in water irradiated with an attenuating sinusoidal ultrasound wave. The computations were made for different operating conditions of frequency (355–1000 kHz), acoustic intensity (1–5 W/cm²), and liquid temperature (10–30°C). The contribution of the acoustic wave attenuation on the overall effect of depth was appreciated for the different conditions. It was found that the acoustic generation of hydrogen diminished hardly with increasing depth up to z = 8 m, and the depth effect was strongly operating parameter-dependent. The sound wave attenuation played a crucial role in quenching H₂ yield, particularly at higher z. The reduction of the H₂ yield with depth was more pronounced at higher frequency (1000 kHz) and lower temperature (10°C) and acoustic intensity (1 W/cm²). The attenuation of the sound wave may contribute up to 100% in the overall reductive effect of depth toward H₂ production rate. This parameter could be imperatively included when studying all aspects of underwater acoustic cavitation.     

ASPECTS OF THE UNDERWATER LIGHT FIELD OF EIGHT CENTRAL NEW YORK LAKES1

ABSTRACT: The underwater light field of eight central New York lakes, which represent a wide range of trophic state, was characterized through paired measurements of Sechi disc transparency (SD, m) and diffuse light attenuation (K_d, m^?1). A total of 90 paired measurements are included in the data base. Substantial variability in the K_d SD product with time within individual systems, and amongst systems, was observed, which indicates differences in the relative contributions of absorption and scattering to attenuation. More than 50 percent of the temporal variability in K_d was attributable to attendant variations in chlorophyll a (C, mg m^?3) in only two of the lakes. Estimates of the adsorption (a, m^?1) and scattering (b, m^?1) coefficients based on paired K_d and SD measurements compared well with more precise determinations available for one of the lakes. Determinations of a and b for the eight lakes, from SD and K_d measurements, indicated great system-specificity and temporal variability in these characteristics. The temporal variability in relative contributions of a and b to K_d is consistent with covariation of different attenuating components and the lack of correlation between C and K_d in most of the study lakes.     

Assessment of the Microbiological Quality of Clarias gariepinus Exposed to an Industrial Effluent in Nigeria

The microbiological impact of a detergent and soap industries effluent on Clarias gariepinus was assessed under laboratory conditions. The heterotrophic bacterial count obtained from fish surfaces ranged from 1.2 × 10²−2.0 × 10²cfu/ml amongst the control, while values of 4.8× 10⁶−8.6 × 10⁶ cfu/ml were obtained for the experimental fish exposed to the industrial effluent (0.025 ppm). The fungal count for the controls ranged from 1.2× 10²−1.2 × 10³ cfu/ml; while a range of 1.0 × 10⁶−2.0 × 10⁶ was obtained for the fish exposed to the industrial effluent. While twelve bacterial species were isolated from the fish exposed to the industrial effluent, only two were isolated from the parts of the control fish used in the study. The bacterial species are those in the genera Staphylococcus, Proteus, Streptococcus, Micrococcus, Bacillus, Pseudomonas, Serratia, Enterobacter, and Escherichia. The fungal isolates include Saccharomyces, Aspergillus, Rhodosporium, Candida, Alternaria, and Fusarium. The resistance of the bacterial isolates to the commonly used antibiotics showed that 100% were resistant to Augmentin, Amoxycillin and Cloxacillin, 85.71% to Tetracycline, 80.95% to Cotrimoxazole, 71.43% to Erythromycin, 33.33% to Chloramphenicol, and 28.57% to Gentamicin. Among the eight antibiotics tested, five patterns of multiple drug resistance were obtained, with the number of the antibiotics ranging from 4–8. The public health implications of these observations are discussed.     

Biohythane production from pineapple peel using Methanosarcina mazei enhanced with palm oil mill effluent (POME) sludge in single-stage anaerobic digestion

Biohythane production via single-stage anaerobic digestion (AD) is an effective way for sustainable energy recovery from lignocellulosic biomass. In this paper, biohythane was produced through the AD process from pineapple peel waste substrate using purely cultured Methanosarcina mazei with the enhancement of palm oil mill effluent (POME) sludge as the inoculum. This study focuses on the effects of the lignocellulosic pre-treatment method, the addition of POME sludge into M. mazei culture medium as inoculum, and various operational conditions (food to microorganisms (F/M) ratios, temperature, pH) on gas production performances. The experimental results indicate that these parameters influenced the efficiency of biohythane production by producing the peak maximum biohythane production rate values (HPR_max) and (MPR_max), H₂:CH₄ = 1.93:0.67 L/L-d, and biohythane yield (HY) and (MY), H₂:CH₄ = 1.18:0.55 mL/L-substrate. This study demonstrates that biohythane gas (H₂ + CH₄ + CO₂) production from pineapple waste can be accelerated by M. mazei only with the enhancement of POME sludge through single-stage AD system under mesophilic batch process conditions.     

Comparison of biosorbents with inorganic sorbents for removing copper(II) from aqueous solutions

In comparison with several other reported inorganic sorbents, Camellia tree leaf and primary sludge obtained from a settling tank as a pretreatment to the activated sludge system in a Hong Kong sewage treatment plant were evaluated for removing Cu(II) from aqueous solutions. Experimental data were modeled by the Langmuir isotherm equation to estimate the maximum sorption capacity (q_max). Results show that, at pH 5.6, biosorbents, Camellia tree leaf and primary sludge in particular, exert higher sorption capacities (q_max > 40 mg g⁻¹) than inorganic sorbents, Na-montmorillonite (q_max = 33.3 mg g⁻¹), fly ash (q_max = 18.8 mg g⁻¹), and goethite powder (10.3 mg g⁻¹). Furthermore, a pseudo second-order kinetic model was found to properly describe the experimental data for both bio- and inorganic sorbents. Sorption of Cu(II) on the Camellia tree leaf and primary sludge were much faster than that on the inorganic sorbents. In addition, desorption tests revealed that the desorption capacities of the two biomaterials are higher than the other selected materials; and much more Cu(II) can be retrieved from the Cu(II)-loaded biosorbents. Finally, increasing solution pH was found to greatly increase q_max and accelerate sorption processes.     

The use of regression equations for quality control in a pesticide physical property database

Quality control is a crucial aspect of database management, particularly for physicochemical parameters that are widely used in modeling environmental fate processes. Complete rechecking of original studies to verify environmental fate parameters is time consuming and difficult. This paper evaluates an alternative, more efficient approach to identifying database errors. The approach focuses verification efforts on a targeted subset of entries by making use of the relationship between water solubility (S) and soil organic carbon partition coefficient (K _oc ). Two regression equations, one selected from the literature and one calculated from entries in the database, were used to evaluate the reasonableness of (S, K _oc ) pairs among control compared to the targeted outlier group from a total of 59 pesticides. Our hypothesis was that (S, K _oc ) pairs that lay far from the regression line were more likely to be in error than those that fit the regression. Database values were checked against original studies. Identified errors in the database included coding mistakes, miscalculations, and incorrect chemical identification codes. The error rate in outlier (S, K _oc ) pairs was about twice that of pairs that conformed to the regression equation; however, the error rate differential was probably not large enough to justify the use of this quality control method. Through our close scrutiny of database entries we were able to identify administrative practices that led to mistakes in the data base. Resolution of these problems will significantly decrease the number of future mistakes.     

Operation strategy of a sequencing batch reactor for simultaneous removal of wastewater organic matter and nutrients

The Sequencing Batch Reactor (SBR) system employing activated sludge process is an alternative wastewater treatment technology. A cycle of the conventional SBR system generally consists of five periods, with complete aeration during the React period to oxidize the organic matter and nitrify the ammonium-nitrogen of wastewater. Laboratory-scale reactors were used to evaluate the feasibility of incorporating alternative aerobic-anoxic-aerobic stages within the React period for simultaneous removal of organic matter, N and P. Two cycles of SBR process per day were maintained.Under the operation strategy of 0.75-h fill, 8-h react (with continuous aeration), 3.25-h settle, draw and idle periods, the treatment performance became consistent after running the system for two to four cycles (1–2 days). The percentages of both BOD₅ and COD removal were around 94% from Cycle 2 onwards, the BOD₅ content dropped from initial 251 mg L⁻¹ to less than 14 mg L⁻¹ in the final effluent. A steady nitrification (about 97%) was obtained from Cycle 4 onwards, with 1 mg NH₄⁺-N L⁻¹ and 25 mg NO₃⁻-N L⁻¹ present in the final effluent. This suggested that the time required for SBR system to acclimate and reach an equilibrium state was relatively short when compared with the time needed for continuous flow activated sludge system. The findings also show that 4-h aeration during the react period was long enough to achieve more than 90% nitrification. With the incorporation of a 3-h anoxic stage after the initial 4-h aeration of the react period, a satisfactory denitrification process was observed, with nitrate level dropped from 27 to around 8 mg L⁻¹ within 3 h. The second aeration stage did not cause significant change in wastewater nitrogen content. The wastewater phosphate content declined rapidly during the initial 4-h aeration and P-release was not observed during the anoxic stage. A slight reduction of P was found in the second aeration stage suggesting that more P-uptake occurred in this stage. A 12-h cyclic SBR system with the incorporation of 4-h aerobic, 3-h anoxic and final 1-h aerobic stages into the 8-h react period was demonstrated to be able to remove C, N and P simultaneously.     

The management implications of fine fuel dynamics in Bushlands Surrounding Hobart, Tasmania

Hobart's bushlands consist of eight distinct vegetation types ranging from open woodland to wet forest. Fine fuel accumulation characteristics are distinctive across this range of vegetation types and mostly seem to conform to the function W_t = W_ss(1−e^−kt)+ l·92(e^−kt), although there is considerable scatter around the lines of best fit in many types.This information contributes to determining the applicability and appropriate frequency of controlled burning as a means of reducing fuels to protect life and property from wildfire. Regular burning of grassy vegetation should ensure relatively safe zones within the urban/bush matrix. It is likely that burning heathy forest types at frequencies that would ensure safe fuel loads would be ecologically detrimental. It would be difficult and futile to use fuel reduction burning in wet forest types as a means of protecting life and property. The fuel accumulation characteristics and the existing ecological knowledge of Allocasuarina verticillata shrubland suggests that fuel reduction burning would be counter-productive in this vegetation type.     

Treatment of E. coli HB101 and the tetM gene by Fenton’s reagent and ozone in cow manure

The destruction of antibiotic-resistant microorganisms at the source of contamination is necessary due to their adverse effects and to their increasingly widespread occurrence in the environment. To address this problem, Fenton and ozone oxidation processes were applied to synthetically contaminated cow manure to remove the tetM gene and its host, Escherichia coli HB101. The efficiency of the processes was evaluated by enumeration of E. coli HB101 and by PCR amplification of the tetM gene. The results of this study show that 56.60% bacterial inactivation (corresponding to a 0.36 log reduction) was achieved by a Fenton reagent dose of 50 mM H₂O₂ and 5 mM Fe²⁺ without acidifying the manure. Despite the high organic content of cow manure, 98.50% bacterial inactivation (corresponding to a 1.83 log reduction) was obtained by the ozonation process with an applied dose of 3.125 mg ozone/g manure slurry. The PCR study revealed that the band intensity of the tetM gene gradually decreased by increasing the Fenton reagent and the applied ozone dose. However, significantly high doses of oxidants would be required to completely eliminate bacterial pollution in manure.     

Study on the failure mechanism of potassium-based sorbent for CO2 capture and the improving measure

With thermogravimetric apparatus (TGA), X-ray diffraction (XRD) and barium sulfate gravimetric methods, the carbonation reactivities of K₂CO₃ and K₂CO₃/Al₂O₃ in the simulated flue gases with SO₂ are investigated and the reaction equations are inferred. Results show that there are KHCO₃ and K₂SO₃ generated. The generation K₂SO₃ reduces the utilization ratio of the sorbent. H₂O may accelerates the sulfation reaction of AR K₂CO₃ as K₄H₂(CO₃)₃·1.5H₂O is generated in the reaction among K₂CO₃, SO₂ and H₂O. K₂SO₃ is directly generated from sulfation reaction of K₂CO₃/Al₂O₃, because there are K₂CO₃·1.5H₂O and K₂SO₃ generated in the reaction among K₂CO₃/Al₂O₃, SO₂ and H₂O. K₂CO₃·1.5H₂O does not react with SO₂, and K₂CO₃·1.5H₂O/Al₂O₃ reacts with SO₂ slowly. Compare with the reaction process without H₂O pretreatment, the reaction rates of KAl30 increased after H₂O pretreatment and the failure ratio is about a half of that without H₂O pretreatment. So, K₂CO₃/Al₂O₃ shows good carbonation and anti-sulfation characteristic after H₂O pretreatment.     

Influence of compost amendment rate and level of compaction on the hydraulic functioning of soils

There has been widespread interest in using compost to improve the hydrologic functions of degraded soils at construction sites for reducing runoff and increasing infiltration. The objective of this study was to determine the effects of compost amendment rate on saturated hydraulic conductivity (K_s) and water retention in order to identify target compost rates for enhancing soil hydrologic functions. Samples were prepared with three soil textures (sandy loam, silt loam, and sandy clay loam), amended with compost at 0%, 10%, 20%, 30%, 40%, and 50%. All soils were tested at a porosity of 0.5 m³/m³, and the sandy loam was further tested at high (0.55 m³/m³) and low (0.4 m³/m³) porosities. The K_s and water retention data were then used to model infiltration with HYDRUS-1D. With increasing compost amendment rate, K_s and water retention of the mixtures generally increased at the medium porosity level, with more compost needed in heavier soils. As porosity decreased in the sandy loam soil, the amount of compost needed to improve K_s rose from 20% to 50%. Water distribution in pore fractions (gravitational, plant-available, and unavailable water) depended on texture, with only the highest compost rates increasing plant-available water in one soil. Results suggest soil texture should be taken into consideration when choosing a compost rate in order to achieve soil improvement goals. Hydrologic benefits may be limited even at a high rate of compost amendment if soil is compacted.     

Evaluation of Fenton and ozone-based advanced oxidation processes as mature landfill leachate pre-treatments

Fenton treatment (Fe²⁺/H₂O₂) and different ozone-based Advanced Oxidation Processes (AOPs) (O₃, O₃/OH⁻ and O₃/H₂O₂) were evaluated as pre-treatment of a mature landfill leachate, in order to improve the biodegradability of its recalcitrant organic matter for subsequent biological treatment. With a two-fold diluted leachate, at optimised experimental conditions (initial pH 3, H₂O₂ to Fe²⁺ molar ratio of 3, Fe²⁺ dosage of 4 mmol L⁻¹, and reaction time of 40 min) Fenton treatment removed about 46% of chemical oxygen demand (COD) and increased the five-day biochemical oxygen demand (BOD₅) to COD ratio (BOD₅/COD) from 0.01 to 0.15. The highest removal efficiency and biodegradability was achieved by ozone at higher pH values, solely or combined with H₂O₂. These results confirm the enhanced production of hydroxyl radical under such conditions. After the application for 60 min of ozone at 5.6 g O₃ h⁻¹, initial pH 7, and 400 mg L⁻¹ of hydrogen peroxide, COD removal efficiency was 72% and BOD₅/COD increased from 0.01 to 0.24. An estimation of the operating costs of the AOPs processes investigated revealed that Fe²⁺/H₂O₂ was the most economical system (8.2 € m⁻³ g⁻¹ of COD removed) to treat the landfill leachate. This economic study, however, should be treated with caution since it does not consider the initial investment, prices at plant scale, maintenance and labour costs.     

Growth and macronutrient removal of water hyacinth in a small secondary sewage treatment plant

Studies have been made of the growth characteristics of water hyacinth, Eichhornia crassipes (Mart.) Solms, and its ability to remove N, P and K, in a secondary settling pond of a small secondary sewage treatment plant serving both the academic and residential blocks of the Swire Marine Laboratory, University of Hong Kong. The treatment plant consists of, in series, a primary settling tank, a trickling filter compartment and a secondary settling pond from which part of the treated wastewater is recycled to the primary settling tank while the remaining effluent (1 to 2 m³ daily) mixes with and hence is diluted by the outflowing seawater from the aquarium system of the Swire Marine Laboratory before discharge to the sea. Samples of wastewater have been taken regularly from the primary sedimentation pond, the outflow of the trickling filter, the secondary settling pond and the effluent of the treatment plant (before mixing with aquarium outflow) since January, 1992. Physical, chemical and biological characteristics of the samples have been determined and are typical of secondary effluents, with a mean pH of about 7.5, total solids 1200 mg L⁻¹, suspended solids 45 mg L⁻¹, conductivity 2000 μS cm⁻¹, salinity 1 ppt, dissolved oxygen 2 mg L⁻¹, BOD₅ 45 mg L⁻¹, Kjeldahl-N 30 mg L⁻¹, NH₄,-N 25 mg L⁻¹, NO₃-N 4 mg L⁻¹, total P 10 mg L⁻¹, K 35 mg L⁻¹ and total coliforms of less than 10⁵ colonies 100 ml⁻¹.Water hyacinth plants have been stocked in the secondary settling pond as an integral part of the treatment plant so as to improve the quality of, as well as to retrieving and recycling nutrient elements from, the wastewater. The plants are periodically harvested to maintain an active growing crop. The growth rate, standing crop biomass, tissue nutrient composition, nutrient storage and accumulation rate of two growth cycles, one from February 25 to March 18 (mean temperature 17.6°C) and the other from 22 April to 12 May (24.8°C) are reported. The water hyacinth assumed a relatively high standing crop biomass of 10 kg m⁻² (5 to 6 t DM ha⁻¹), and growth rates of 48 and 225 g m⁻² day⁻¹, respectively, for the first and second growth period. Nutrient storage capacities were relatively high, at about 20, 7.5 and 16.5 g m⁻² for N, P and K, respectively. The nutrient composition was very high, reaching 5.42% for N, 1.97 for P, and 4.57 for K. Both the stem and lamina accumulated high levels of N, while the petiole had the highest level of P and K. Apart from nutrient removal, the water hyacinth also helped to decrease the suspended solids, BOD₅ value and total coliforms of the wastewater.It is concluded that water hyacinth improves the quality of wastewater in such small-scale sewage treatment plants and it is recommended that frequent harvests of water hyacinth would increase the treatment efficiency, especially during the active growing season with high temperatures coupled with intense solar radiation.     

Influence of Prey and Nutritional Status on the Rate of Nitrogen Uptake by Prymnesium parvum (haptophyte)1

Lindehoff, Elin, Edna Granéli, and Patricia M. Glibert, 2010. Influence of Prey and Nutritional Status on the Rate of Nitrogen Uptake by Prymnesium parvum (Haptophyte). Journal of the American Water Resources Association (JAWRA) 46(1):121-132. DOI: 10.1111/j.1752-1688.2009.00396.x Abstract: We studied how the specific nitrogen (N) uptake rates of nitrate (NO₃⁻), urea, and the amino acids, glutamic acid and glycine, by Prymnesium parvum were affected by (1) the change from N-deficient status to N-sufficient status of the P. parvum cells, (2) presence of prey from a natural Baltic Sea plankton community, and (3) the composition of prey as affected by additions of terrestrial originated dissolved organic matter (DOM) or inorganic nutrients. Nitrogen-deficient P. parvum (16 μM NO₃⁻ and 4 μM PO₄⁻, molar N:P ratio of 4:1) were mixed with a natural Baltic plankton community and given PO₄³⁻ and (1) NO₃⁻ (control) or (2) high molecular weight DOM, >1 kDa concentrated from sewage effluent (+DOM), in a molar N:P ratio of 9-10:1. With additions of ¹⁵N-enriched substrates, rates of N uptake from NO₃⁻, urea, and the amino acids glycine and glutamic acid were measured every 24 h for 72 h. Initial N-deficient P. parvum were highly toxic (3.7 ± 0.9 × 10⁻⁴ mg Sap equiv/cell) and toxic allelochemicals were released into the medium causing the natural plankton community to lyse. Rates of N uptake differed between the “control” and the “+DOM” treatments over time; total (sum of the N substrates measured) absolute uptake rates (ρ_cell, fmol N/cell/h) at ambient culture conditions were significantly higher (ANOVA, p < 0.05) in the more toxic “control” treatments compared with the “+DOM” treatments after 48 h. In the “control” treatment, the total ρ_cell increased significantly (ANOVA, p < 0.01) from time 0 to 48 h, while in the “+DOM” treatment there was no significant increase. Released organic nutrients from the lysed plankton cells may have increased uptake rates of amino acids and urea by P. parvum. All uptake rates declined in all treatments by 72 h. Total dissolved N uptake rates at ambient culture conditions were estimated to make up about 10% of the N P. parvum are potentially capable of ingesting from particulate prey.