Biosorption with autochthonous and allochthonous fungal biomasses for bioremediation and detoxification of landfill leachate

Landfill leachates are not adequately treated in traditional wastewater treatment plants, on account of their problematic peculiarities: i.e., dark colour, high concentration of recalcitrant pollutants and COD, and high toxicity. In this work, 19 biomasses (15 autochthonous and 4 allochthonous) were exploited in biosorption treatment for the remediation of a leachate (influent) and the effluent coming from the biological oxidation with activated sludge and nitrification–denitrification treatment. The effects of the initial pH, the biomass amount, and the medium for the biomass pre-culture were considered. The best configuration was: pH 5, 5 g L^??1 biomass cultivated on STY medium. Eventually, the two most effective biomasses, Cunninghamella bertholletiae MUT 2861 and Aspergillus fumigatus MUT 4050, were used in consecutive 2 h cycles in a batch biosorption experiment. The effectiveness of the treatment decreased in subsequent cycles in terms of decolourisation (31–15%). COD, Cl^?, SO₄^2?, total N, and toxicity were removed mainly in the second cycle of treatment (up to ??36, ??12, ??15, ??17 and ??49%, respectively). The results suggest that the effluent toxicity was basically due to uncoloured substances, which were mainly removed after coloured molecules.     

Removal of phenolic compounds in olive mill wastewater by silica–alginate–fungi biocomposites

This study aims to attempt a treatment strategy based on fungi immobilized on silica-alginate (biocomposites) for removal of phenolic compounds in olive oil mill wastewater (OMW), OMW supplemented (OMWS) with phenolic compounds and water supplemented (WS) with phenolic compounds, thus decreasing its potential impact in the receiving waters. Active (alive) or inactive (death by sterilization) Pleurotus sajor caju was encapsulated in alginate beads. Five beads containing active and inactive fungus were placed in a mold and filled with silica hydrogel (biocomposites). The biocomposites were added to batch reactors containing the OMW, OMWS and WS. The treatment of OMW, OMWS and WS by active and inactive biocomposites was performed throughout 28 days at 25 °C. The efficiency of treatment was evaluated by measuring the removal of targeted organic compounds, chemical oxygen demand (COD) and relative absorbance ratio along the time. Active P. sajor caju biocomposites were able to remove 64.6–88.4 % of phenolic compounds from OMW and OMWS and 91.8–97.5 % in water. Furthermore, in the case of OMW there was also a removal of 30.0–38.1 % of fatty acids, 68.7 % of the sterol and 35 % of COD. The silica–alginate–fungi biocomposites showed a high removal of phenolic compounds from OMW and water. Furthermore, in the application of biocomposites to the treatment of OMW it was observed also a decrease on the concentration of fatty acids and sterols as well as a reduction on the COD.     

Comparison of Fenton,ultraviolet–Fenton and ultrasonic–Fenton processes on organics and colour removal from pre-treated natural gas produced water

Produced water (PW) from natural gas field, characterized with high organic contents, has brought high environmental concerns world widely. Fenton and enhanced Fenton technologies were considered as the potential methods to degrade the organic contaminates in the PW, but with very limited data or reference. Here, we examined the optimum conditions of Fenton on organics and colour removal from natural gas PW after coagulation pre-treatment. Simultaneously, the optimal Fenton process integrated with ultraviolet (UV) and ultrasonic (US) irradiation were applied to enhance pollutants removal efficiencies. The optimal Fenton conditions were found at 60 min with molar ratios of 6:1 and 25:1 for H₂O₂/COD and H₂O₂/Fe²⁺, respectively and the initial pH of 3. Among these the three treatment processes, chemical oxygen demand (COD), total organic carbon, 5-day biological oxygen demand (BOD₅), and colour removal efficiencies were highest during UV–Fenton (82, 73, 68, and 95%,) followed by US–Fenton (79, 70, 66, and 95%) and Fenton treatment (70, 58, 51, and 92%), respectively. High biodegradability (BOD₅/COD) was also observed after UV–Fenton process (0.76) than the others (both 0.73). The current study showed a satisfactory carbon and colour removal efficiencies from PW using different Fenton processes; however, there still is a need for final polishing such as biological treatment or low cost constructed wetland before discharge. This study can be a good reference for engineering application PW treatment.     

Electro-chemical mineralization of recalcitrant indole by platinum-coated titanium electrode: multi-response optimization,mechanistic and sludge disposal study

Indole is a highly recalcitrant aromatic heterocyclic organic compound consisting of a five-membered nitrogen-containing pyrrole ring fused to a six-membered benzene ring. This study presents the results of the electro-chemical mineralization of indole in an aqueous solution using platinum-coated titanium (Pt/Ti) electrode. A central composite design was used to investigate the effect of four parameters namely initial pH (pH_o), current density (j), conductivity (k) and treatment time (t) at 5 levels. Multiple responses namely chemical oxygen demand (COD) removal (Y ₁) and specific energy consumption (Y ₂) were simultaneously maximized and minimized, respectively, by optimizing the parameters affecting the mineralization of indole by using the desirability function approach. At the operating conditions of pH 8.6, j = 161 A/m², k = 6.7 mS/cm and t = 150 min, 83.8% COD removal with specific energy consumption of 36.3 kWh/kg of COD removed was observed. Ultra performance liquid chromatography, UV–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry of the indole solution were performed at the optimum condition of the treatment so as to report a plausible mechanism of indole degradation. Field emission scanning electron microscopy analysis of electrodes before and after treatment was performed for determining the changes on anode surface during the treatment. Thermal analysis of the solid residue (scum) obtained was also performed for exploring its disposal prospects. Present study shows that electro-chemical oxidation can be used for mineralization of nitrogenous heterocyclic compounds such as indole.     

Exploring the diverse potentials of <Emphasis Type="Italic">Planococcus</Emphasis> sp. TRC1 for the deconstruction of recalcitrant kraft lignin

Kraft lignin (KL) is the chief contaminant which is responsible for dark coloration, toxicity and high chemical oxygen demand (COD) of paper pulp mill effluent. The present study investigated the diverse potentials of Planococcus sp. TRC1 in the biodegradation of KL. Preliminary evaluation indicated that the strain was able to grow on broad spectrum of lignin-derived compounds, decolorize lignin-mimicking dyes and catabolize substrates of ligninolytic enzymes. Response surface methodology (RSM) was executed to perform the optimization of different process parameters. The results displayed that Planococcus sp. TRC1 could completely utilize 100 mg L^?1 of KL and 78% of 200 mg L^?1 of KL as sole source of carbon with concurrent reduction in COD and color. The biokinetic details of KL biodegradation showed that the values of \(\mu^{*}\), µ _max, \(q^{*}\) and q _max were 0.018 h^?1, 0.01 h^?1, 0.023 g g^?1 h^?1 and 0.05 g g^?1 h^?1, respectively. UV–visible spectrophotometry, SEM and FTIR indicated the significant alterations in the surface morphology, functional groups and chromophores during the course of biodegradation. XRD revealed the emergence of peak signifying the formation of low molecular weight intermediates after bacterial treatment. Considering the environmental impact, bacterial-treated KL illustrated less phytotoxicity using Vigna radiata seed bioassay. These results suggested that Planococcus sp. TRC1 could be a promising strain for the degradation of KL in an ecofriendly way.     

Mechanism of efficient nutrient removal and microbial analysis of a combined anaerobic baffled reactor–membrane bioreactor process

A combined ABR–MBR process consisting of an anaerobic baffled reactor (ABR) combined with an aerobic membrane bioreactor (MBR) treating municipal wastewater was investigated at controlled pH range 6.5–8.5 and at constant temperature 25 ± 1 °C. Total nitrogen (TN), ammonia (NH₄ ⁺–N), total phosphorus (TP), and chemical oxygen demand (COD) removal performances were evaluated by analyzing the mechanism for efficient nutrient removal. The results showed that the average removal rates of COD, NH₄ ⁺–N, TN, and TP reached 93, 99, 79, and 92 %, respectively, corresponding with the COD, NH₄ ⁺–N, TN, and TP effluent of 24 (18–31), 0.4 (0–0.8), 10.6 (8.8–12.9), and 0.31 (0.1–0.5) mg/L under the operational condition of hydraulic retention time (HRT) 7.5 h, recycle ratio 200 %, and dissolved oxygen 3 mg/L. The MBR enhanced NH₄ ⁺–N, TN, and TP removal rates of 13, 10, and 18 %, respectively, and the membrane retention reduced TP 0.17 mg/L. The process was able to maintain a stable performance with high-quality effluent. Analysis of the results by fluorescence in situ hybridization showed that the abundance of ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and phosphorus accumulating organisms as percentages of all bacteria in each compartment was stable. The enriched microorganisms in the system appear to be the main drivers of the process efficient for nutrient removal.     

Improvement on the treatment of thick oil sewage by using integrated biochemical treatment technology

Sewage treatment station in oilfield needs a new process to meet the desired requirements. A new process was proposed to meet the discharge standards, which consisted of the following sub-processes: electrochemical treatment → coagulation treatment → integrated biochemical treatment of moving bed biofilm reactor and membrane bio-reactor → combined treatment process of macroporous adsorption resin. Electrochemical treatment included 5 electrolytic cells, total volume of which was 10 L. The PFS was chosen as the coagulants in the coagulation treatment, and the removal rate of COD could reach 66% when the dosage of PFS was 500 mg/L. The biochemical treatment consisted of anoxic tank, aerobic tank and membrane zone, and the removal rate of COD was about 55–70% when HRT was 12 h. SD300 resin was chosen as the best adsorbent in the treatment using macroporous adsorption resin. In addition, the effluent COD after coagulation treatment process becomes about 180 mg/L, the effluent COD after biological treatment becomes about 50 mg/L, and the last effluent COD with the macroporous adsorption resin becomes about 20 mg/L. The three-dimensional fluorescence spectrum was used to analyze the differences in types of organic matters in water samples between the raw water and the treated one. The results demonstrated that the new process meets the needs of wastewater treatment.     

Effect of leachate loading rate and incubation period on the treatment efficiency by T. versicolor immobilized on foam cubes

This study focuses on treatment of landfill leachate in column experiments by immobilized Trametes versicolor on polyurethane foam, collected from Nonthaburi landfill site, Thailand. In this study, glucose was used as a co-substrate. The effect of biomass growth on color removal was observed by immobilizing fungi on polyurethane foam. The same immobilized fungi were used for four cycles of 5 days each to find the reuse of fungi. Leachate was diluted to see the effect of organic loading on color removal. At optimum pH of 4 and in 20 days with 3 g/L of glucose, the fungi could decolorize 78 % and 63 % for 5-times dilution and concentrated leachate, respectively, using immobilized fungi after 4 days initial growth. Fungi could also reduce biological oxygen demand and chemical oxygen demand of 52 % and 42 % (with initial biological oxygen demand and chemical oxygen demand of 48,900 and 96,512 mg/L), respectively, with glucose 3 g/L in concentrate leachate and with 4 days initial immobilization of fungi on polyurethane foam. About 1–6% higher color removal was observed on day 20 with 15 days fungi immobilization initially as compared to 4 days immobilization. Higher removal efficiency was observed for the same leachate after dilution due to reduction in organic loading. Addition of co-substrate enhances significantly removal of color, biological oxygen demand and chemical oxygen demand. Chemical oxygen demand removal reached to 0.6 mg/mg of biomass with the co-substrate. Therefore, white rot fungi can be considered as potentially useful microorganisms in landfill leachate treatment.     

Treatment of vinasse by electrochemical oxidation: evaluating the performance of boron-doped diamond (BDD)-based and dimensionally stable anodes (DSAs)

The removal of colour and organic compounds from vinasses derived from the wine distillery industry was studied using boron-doped diamond-based electrodes and dimensionally stable anodes. The maximum reduction of organic compounds and colour was attained with the use of boron-doped diamond-based electrode after 10 h of operation at a current density of 6.6 mA cm^?2. The current efficiency obtained was about 90% with a specific energy consumption (measured in terms of removal of chemical oxygen demand) of 17 kWh kg^?1 COD removed. The dimensionally stable anodes were capable of removing 6–47% of the organic material and reached 60% decolourisation but with a lower current efficiency (between 85 and 10%) and much higher specific energy consumption values. The anaerobic digestion of vinasse after 1 h of treatment using boron-doped diamond-based electrode showed an effective mineralisation of the organic matter contained in the sample leading to an increase in methane production during anaerobic digestion.     

On-site treatment of textile yarn dyeing effluents using an integrated biological–chemical oxidation process

This paper reports the results of the treatment of a yarn dyeing effluent using an integrated biological–chemical oxidation process. In particular, the biological unit was based on a sequencing batch biofilter granular sludge reactor (SBBGR), while the chemical treatment consisted of an ozonation step. Biological treatment alone was first performed as a reference for comparison. While biological treatment did not produce an effluent for direct discharge, the integrated process assured good treatment results, with satisfactory removal of chemical oxygen demand (up to 89.8 %), total nitrogen (up to 88.2 %), surfactants (up to 90.7 %) and colour (up to 99 %), with an ozone dose of 110 mg of ozone per litre of wastewater. Biomass characterization by fluorescence in situ hybridization has revealed that filamentous bacteria represented about 20 % of biomass (coherently with high sludge volume index values); thanks to its special design, SBBGR guaranteed, however, stable treatment performances and low effluent suspended solids concentrations, while conventional activated sludge systems suffer from sludge bulking and even treatment failure in such a condition. Furthermore, biomass characterization has evidenced the presence of a shortcut nitrification–denitrification process.     

Coupling short-time sequencing batch reactor and coagulation–settling process for co-treatment of landfill leachate with raw municipal wastewater

The co-treatment of landfill leachate (LFL) with municipal wastewater (MWW) using shortcut sequencing batch reactor combined with coagulation–settling process (SBR + CS) was investigated. Four ratios of LFL to MWW volume (v/v) were used during experiments including the ratios 1:9, 2:8, 3:7 and 5:5. The average quality of the LFL was chemical oxygen demand (COD) of 20,800 mg L^?1 and NH₄-N of 2,645 mg L^?1. The SBR-treating LFL in six series where mixing aeration and settling phases were varied from 4 to 14 h was combined with coagulation (FeCl₃, Al₂(SO₄)₃) with an interval of 2 h. It was found that ratio (1:9) of leachate to MWW under aeration and mixing phase of 4 h with settling time of 1.5 h exhibited the highest ability to remove both COD and NH ₄ ⁺ -N, 99% and 85%, respectively. The short-time sequential batch reactor was tested for the treatment of raw LFL, and only 47% and 23% removal of COD and NH ₄ ⁺ -N, respectively, could be achieved.     

Physical–chemical treatment process optimization for high polluting dairy effluents prior fermentation

Among dairy effluents, bactofugate (B) and decreaming racking water (D) were identified as the most polluting due to their organic load content expressed in the chemical oxygen demand (156–240 g·L^?1). Joining the plant wastewater, such effluents contribute to the increase of the polluting load of the wastewater treatment plant input which disturbs the treatment performance. This work proposes an upstream segregation of those dairy effluents for combined physical–chemical and biological treatment. An experimental design was proposed to investigate initial pH, applied temperature and exposure time factor effects on the thermal coagulation process. The fermentation of the resulted supernatants using Lactobacillus lactis ssp. lactis was performed. The optimized thermal coagulation pretreatment was obtained at (pH; T(°C); t(min)): 6, 60 °C and 5 min, with both (B) and (D) effluents. Resulted clarified whey sugar, protein and fat contents were assessed. The physical–chemical treatment resulted in considerable organic matter removal: 45% for (B) samples and 31% for (D) samples of proteins content and almost the total fat content. However, there is no considerable effect on the sugar content reduction, which remains responsible for the major fraction of the whey residual chemical oxygen demand (COD). Clarified whey fermentation using Lactococcus lactis ssp. lactis strain induced important sugar consumption rates. Therefore, important sugar consumption rates were recorded and the COD removal efficiency was improved. The recorded global COD removal efficiency was of about 93%. The proposed combined physical–chemical and biological processes for dairy effluents pretreatment allowed not only to reduce the effluents polluting load, but also to valorize wheys by producing valuable components.     

Photocatalytic activity evaluation of TiO<Subscript>2</Subscript> nanoparticles based on COD analyses for water treatment applications: a standardization attempt

Evaluation of the photocatalytic activities of TiO₂ nanomaterials based on the chemical oxygen demand (COD) analyses under identical experimental conditions was not previously reported. In this work, COD has been selected as an adequate industrial water quality measure toward the establishment of a representative standard test method. The initial COD values of six organic pollutants representing dye, surfactants, phenols and alcohol were set at 30 ± 2 mg/L. Ten of different commercial and synthesized TiO₂ samples representing anatase, rutile and mixed phases were used and characterized. The data of photocatalytic processes were compared to that obtained using the commonly widespread Degussa-P25 TiO₂ (TD). The COD of all pollutants was completely removed by TD at UV exposure dose ≤9.36 mWh/cm². Consequently, the maximum irradiation dose was set at this value in all experiments. The percentages of COD removal as well as the values of the accumulated UV doses required for complete removal of pollutants were measured using the different TiO₂ samples. TiO₂ samples show different performance abilities toward the various pollutants compared to TD. Based on the obtained data, TiO₂ photocatalysts were divided into two categories according to the hydroxyl radical formation rates. Comparison with previous studies reveals that the photocatalytic efficiency evaluation depends on the method of measurement. COD is recommended to be used as an adequate technique of analysis that meets the purpose of water treatment applications.     

Comparative performance evaluation of physicochemical treatment processes for simulated dairy wastewater

In the present study, the effectiveness of physicochemical treatment processes (coagulation and Fenton’s oxidation) was investigated for simulated dairy wastewater (pH = 7.3, chemical oxygen demand (COD) = 3600 mg/l, 5-day biochemical oxygen demand (BOD₅) = 1950 mg/l, total Kjeldahl nitrogen (TKN) = 87 mg/l, and total phosphorous (TP) = 14 mg/l). Plain and ballasted coagulation runs were carried out in a jar apparatus, while Fenton’s oxidation was performed in a three-neck glass reactor. Ballasted coagulation caused an enhancement in the settling rate of sludge though no significant enhancement in the removal of organics was observed. Individually, coagulation and Fenton’s oxidation processes resulted in ~67 and 80 % COD removals, respectively, from the wastewater. The sequential treatment exploring coagulation followed by Fenton’s oxidation showed overall COD, BOD₅, TKN, and TP reductions of ~93, 97, 84, and 70 %, respectively, from the wastewater. However, a biological post-treatment would be required to achieve the effluent discharge standards. The removal of proteins, fats, and amino acids from wastewater was confirmed from Fourier transform infrared analysis of the settled sludge (obtained after coagulation process). Preliminary cost analysis suggested coagulation and the sequential treatment (i.e. coagulation followed by Fenton’s oxidation) as the preferred options.     

Efficient removal of hexavalent chromium from aqueous solutions using autohydrolyzed Scots Pine (Pinus Sylvestris) sawdust as adsorbent

In this work, a low-cost lignocellulosic adsorbent with high biosorption capacity is proposed, suitable for the efficient removal of hexavalent chromium from water and wastewater media. The adsorbent was produced by autohydrolyzing Scots Pine (Pinus Sylvestris) sawdust. The effect of the autohydrolysis conditions, i.e., pretreatment time and temperature, on hexavalent chromium biosorption was investigated using energy-dispersive X-ray spectroscopy (EDS) and UV–visible spectrophotometry. The Freundlich, Langmuir, Sips, Radke-Prausnitz, Modified Radke-Prausnitz, Tóth, UNILAN, Temkin and Dubinin-Radushkevich adsorption capacities and the rate constant values for pseudo-first- and pseudo-second-order kinetics indicated that the autohydrolyzed material exhibits significantly enhanced hexavalent chromium adsorption properties comparing with the untreated sawdust. The Freundlich’s adsorption capacity K _F increased from 2.276 to 8.928 (mg g^?1)(L mg^?1)^1/n , and the amount of hexavalent chromium adsorbed at saturation (Langmuir constant q _m) increased from 87.4 to 345.9 mg g^?1, indicating that autohydrolysis treatment at 240 °C for 50 min optimizes the adsorption behavior of the lignocellulosic material.     

A novel approach for textile dye degradation by zinc,iron–doped tin oxide/titanium moving anode

The present contribution reports a moving iron (Fe), zinc (Zn)–doped tin oxide/titanium (SnO₂/Ti) anode-based system designed and operated for the electro-oxidation of methyl orange dye effluent. Electrochemical oxidation of the dye was carried out at a current density of 1.8 A/dm² for 120 min. Similar experiments were repeated with pure SnO₂-based static and moving anode-based systems and the Fe, Zn-doped SnO₂ static anode-based electro-oxidation system. Post oxidation, the surface of the electrodes was critically examined by scanning electron microscopy. Dye samples were analysed at regular intervals during the electro-oxidation process by chemical oxygen demand and colour removal measurements and characterized by UV–Vis spectroscopy and Fourier transform infrared spectroscopy at the end of the oxidation process. The obtained results elucidate the superiority of Fe, Zn-doped SnO₂/Ti moving anode-based system for methyl orange dye effluent electro-oxidation. The moving anode prevents passive layer formation and decreases polarization resistance. Doping of Fe and Zn provides the anode-enhanced mechanical strength and electrocatalytic activity. The combined effects of axial anode movement and doping are responsible for improved performance of the moving anode system reported in this contribution.     

Photocatalytic degradation of azo dye Orange II in aqueous solutions using copper-impregnated titania

During dyeing process, industries consume large quantity of water and subsequently produce large volume of wastewater. This wastewater is rich in color and contains different dyes. Orange II is one of them. In this article, metal-impregnated TiO₂ P-25 catalyst was used to enhance the photocatalytic degradation of Orange II dye. Photodegradation percentage was followed spectrophotometrically by the measurements of absorbance at λ _max = 483 nm. The effect of copper-impregnated TiO₂ P-25 photocatalyst for the degradation of Orange II has been investigated in terms of percentage removal of color, chemical oxygen demand (COD) and total organic carbon (TOC). As such 98 % color removal efficiency, 97 % percentage removal of COD and 89 % percentage removal of TOC was achieved with TiO₂ P-25/Cu catalysts under typical conditions. Copper-impregnated TiO₂ P-25 photocatalyst showed comparatively higher activity than UV/H₂O₂ homogeneous photodegradation. The relative electrical energy consumption for photocatalytic degradation was considerably lower with TiO₂ P-25/Cu photocatalyst than that with homogeneous photodegradation. Transmission electron microscopic analysis was used for catalyst characterization.     

Release characteristics of molasses from a well-type barrier system in groundwater: a large test tank study for nitrate removal

A pilot-scale study was conducted to characterize the performance of molasses' release from a well-type barrier system harboring solidifying molasses named slowly released molasses (SRM) as a reactive medium to promote indigenous denitrifying activity. A SRM rod was made by mixing molasses with paraffin wax, cellulose, and silica sands in a cylindrical mold. Two SRM systems harboring 30 and 60 SRM rods, referred to as Systems A and B, respectively, were constructed in a large flow tank (L × W × D = 8 m × 4 m × 2 m) filled with natural sands. These two systems continuously delivered molasses with groundwater flow over 96 days, with decreasing molasses' concentrations ranging from 763 to 95 and 1,150 to 183 mg L^?1 as chemical oxygen demand values (COD) for Systems A and B, respectively. From simulation results with an aid of the upscaled mass transfer function (MTF) model, the molasses' mass flux was slowly decreased with time, exhibiting 57, 11, and 3 mg COD day^?1 in 10, 100, and 365 days in System A, and 138, 25, and 6 mg COD day^?1 in System B, respectively; 90, 70, and 50 % of total molasses' mass remained after 12, 63, and 267 days in System A and 12, 65, and 291 days in System B, respectively. This study demonstrates that SRM system can provide a remedial alternative for long-term in situ treatment of nitrate-contaminated groundwater.     

Cell Size-Dependent Effects of Solar UV Radiation on Primary Production in Coastal Waters of the South China Sea

In order to examine the effects of solar ultraviolet radiation (UVR, 280–400 nm) on photosynthesis of differently cell-sized phytoplankton, natural phytoplankton assemblages from the coastal waters of the South China Sea were separated into three groups (>20, 5–20, and <5 μm) and exposed to four different solar UV spectral regimes, i.e., 280–700 nm (PAR?+?UVR), 400–700 nm (PAR), 280–400 nm (UV-A?+?B), and 315–400 nm (UV-A). In situ carbon fixation measurements revealed that microplankton (>20 μm) efficiently utilized UV-A for photosynthetic carbon fixation, with assimilation number of up to 1.01 μg C (μg chl a)^?1?h^?1 under 21.4 W?m^?2 UV-A alone (about half of noontime irradiance at the surface), about 40 % higher than nanoplankton (5–20 μm). UV-B (280–315 nm) of 0.95 W?m^?2 reduced the carbon fixation by approximately 20 and 57 % in microplankton and nanoplankton assemblages, respectively. In contrast, smaller picoplankton (<5 μm) was unable to utilize UV-A for the photosynthetic carbon fixation. In addition, only micro-sized assemblages demonstrated the UV enhancement on their primary productivity in the presence of PAR, by about 8 % under moderate intensities of solar radiation.     

Tunisian landfill leachate treatment using <Emphasis Type="Italic">Chlorella</Emphasis> sp.: effective factors and microalgae strain performance

The potential of the autoclaved Tunisian landfill leachate treatment using microalgae (Chlorella sp.) cultivation was investigated in this study. Landfill leachate was collected from Borj Chakir landfill, Tunisia. A full factorial experimental design 2² was proposed to study the effects of the incubation time and leachate ratio factors on the organic matter removal expressed in chemical oxygen demand (COD) and ammoniacal nitrogen (NH₄─N) and on the biological response of Chlorella sp. expressed by the cell density and chlorophyll content. All experiments were batch runs at ambient temperature (25 ± 2 °C). The Chlorella sp. biomass and chlorophyll a concentrations of 1.2 and 5.32 mg L^?1, respectively, were obtained with 10% leachate spike ratio. The obtained results showed that up to 90% of the ammoniacal nitrogen in landfill leachate was removed in 10% leachate ratio spiked medium with a residual concentration of 40 mg L^?1. The maximum COD removal rate reached 60% within 13 days of incubation time indicating that microalgae consortium was quite effective for treating landfill leachate organic contaminants. Furthermore, with the 10% leachate ratio spiked medium, the maximum lipid productivity was 4.74 mg L^?1 d^?1. The present study provides valuable information for potential adaptation of microalgae culture and its contribution for the treatment of Tunisian landfill leachate.