Simultaneous nutrient removal and lipid production from pretreated piggery wastewater by Chlorella vulgaris YSW-04

The feasibility of using a microalga Chlorella vulgaris YSW-04 was investigated for removal of nutrients from piggery wastewater effluent. The consequent lipid production by the microalga was also identified and quantitatively determined. The wastewater effluent was diluted to different concentrations ranging from 20 to 80 % of the original using either synthetic media or distilled water. The dilution effect on both lipid production and nutrient removal was evaluated, and growth rate of C. vulgaris was also monitored. Dilution of the wastewater effluent improved microalgal growth, lipid productivity, and nutrient removal. The growth rate of C. vulgaris was increased with decreased concentration of piggery wastewater in the culture media regardless of the diluent type. Lipid production was relatively higher when using synthetic media than using distilled water for dilution of wastewater. The composition of fatty acids accumulated in microalgal biomass was dependent upon both dilution ratio and diluent type. The microalga grown on a 20 % concentration of wastewater effluent diluted with distilled water was more promising for generating high-efficient biodiesel compared to the other culture conditions. The highest removal of inorganic nutrients was also achieved at the same dilution condition. Our results revealed the optimal pretreatment condition for the biodegradation of piggery wastewater with microalgae for subsequent production of high-efficient biodiesel.     

Effect of intermittent CO2 enrichment during nutrient starvation on tertiary treatment of wastewater by alginate-immobilized Scenedesmus bicellularis

A method of accelerating the removal of ammonium and phosphate by the unicellular microalga Scenedesmus bicellularis is presented for municipal tertiary wastewater treatment using immobilized cells to obtain a high quality of effluents. Microalgal cells grown in defined medium were harvested by centrifugation and stored at 4°C in the dark for 8 months before immobilization. The concentrated cell suspension was then immobilized in alginate films supported on polypropylene screens. Immobilized cells were incubated in a water-saturated air stream enriched with CO₂ at 750, 1,000, or 1,500 ppm for 3 h periods followed by 2 h periods without enrichment. The quantitative effects of these three CO₂ enrichments on nutrient uptake from secondary municipal wastewater effluent were compared to a control laboratory air at 320 ppm under the same conditions of illumination, photoperiod, and humidity. The exposure cycle of 48-h nutrient deprivation in air with CO₂ enrichment followed by 2 h of nutrient uptake from wastewater was repeated three times with a residual NH₄---N content dropping to 0% after 105 min for the 1,500 ppm CO₂ treatment and to 34% of the initial level after 120 min for the control treatment. Complete PO₄---P removal required more than 2 h. The chlorophyll a contents obtained with 1,000 and 1,500 ppm CO₂ enrichments were comparable. This study establishes that intermittent CO₂ enrichment during nutrient deprivation of immobilized microalgal cells in a water-saturated air stream may accelerate tertiary wastewater treatment.     

Lipid Production for Biofuels from Effluent-based Culture by Heterotrophic Chlorella Protothecoides

The effluent from a continuous-flow stirred tank reactor (CSTR) treating synthetic wastewater was used as an alternative carbon source to glucose for algal biomass and biodiesel production. The influence of the effluent on microalgal cell growth and lipid yield, as well as the utilization of volatile fatty acids (VFAs) in the effluent were investigated. The results indicate that C. protothecoides can proliferate in the CSTR effluent and accumulate biolipid. The final lipid content of the culture with the effluent feeding was 27?±?1.11 % after 168 h cultivation in flasks, which was higher than that with glucose of the same COD concentration. Valeric acid, ethanol, and butyric acid were favorable carbon sources for cell growth. The soluble microbial products (SMP) can be used as a carbon source for cell growth, and the existence of SMP could protect the cell from the inhibition caused by strong VFAs and improve the utilization of VFAs.     

Mixotrophic and photoautotrophic cultivation of 14 microalgae isolates from Saskatchewan, Canada: potential applications for wastewater remediation for biofuel production

Northern regions are generally viewed as unsuitable for microalgal biofuel production due to unfavorable climate and solar insolation levels. However, these conditions can potentially be mitigated by coupling microalgal cultivation to industrial processes such as wastewater treatment. In this study, we have examined the biomass and lipid productivity characteristics of 14 microalgae isolates (Chlorophyta) from the Canadian province of Saskatchewan. Under both photoautotrophic and mixotrophic cultivation, a distinct linear trend was observed between biomass and lipid productivities in the 14 SK isolates. The most productive strain under cultivation in TAP media was Scenedesmus sp.-AMDD which displayed rates of biomass and fatty acid productivities of 80 and 30.7?mg?L^?1?day^?1, respectively. The most productive strain in B3NV media was Chlamydomonas debaryana-AMLs1b which displayed rates of biomass and fatty acid productivities of 51.7 and 5.9?mg?L^?1?day^?1, respectively. In 11 of the isolates tested, secondary municipal wastewater (MCWW) supported rates of biomass productivity between 21 and 33?mg?L^?1?day^?1 with Scenedesmus sp.-AMDD being the most productive. Three strains, Chlamydomonas debaryana-AMB1, Chlorella sorokiniana-RBD8 and Micractinium sp.-RB1b, showed large increases in biomass productivity when cultivated mixotrophically in MCWW supplemented with glycerol. High relative oleic acid content was detected in 10 of the 14 isolates when grown mixotrophically in media supplemented with acetate. There was no detectable effect on the fatty acid profiles in cells cultivated mixotrophically in glycerol-supplemented MCWW. These data indicate that biomass and lipid productivities are boosted by mixotrophic cultivation. Exploiting this response in municipal wastewater is a promising strategy for the production of environmentally sustainable biofuels.     

Survival,Growth and Condition of Freshwater Mussels: Effects of Municipal Wastewater Effluent

Freshwater mussels (Family Unionidae) are among the most imperiled group of organisms in the world, with nearly 65% of North American species considered endangered. Anthropogenic disturbances, including altered flow regimes, habitat alteration, and pollution, are the major driver of this group''s decline. We investigated the effects of tertiary treated municipal wastewater effluent on survivorship, growth, and condition of freshwater mussels in experimental cages in a small Central Texas stream. We tested the effluent effects by measuring basic physical parameters of native three ridge mussels (Amblema plicata) and of non-native Asian clams (Corbicula fluminea), before and after 72-day exposure at four sites above and below a municipal wastewater treatment plant outfall. Survivorship and growth of the non-native Asian clams and growth and condition indices of the native three ridge mussels were significantly higher at the reference site above the outfall than in downstream sites. We attribute this reduction in fitness below the outfall to elevated nutrient and heavy metal concentrations, and the potential presence of other untested-for compounds commonly found in municipal effluent. These results, along with an absence of native mussels below the discharge, indicate a significant negative impact of wastewater effluent on both native and non-native mussels in the stream.     

Performance of an ecological treatment system at three strengths of dairy wastewater loading

Ecological treatment systems, which rely on renewable resources, have successfully treated municipal and industrial effluents with reduced costs compared to conventional methods, but their capacity to treat dairy wastewater is unknown. In order for ecological treatment systems to be practical for agriculture they must be able to treat a significant portion of a dairy's daily wastewater production. In this study, the impact of three strengths of dairy wastewater on effluent water quality was assessed. Three ratios of wastewater and city water—(1) one part wastewater:three parts city water, (2) one part wastewater:one part city water, and (3) two parts wastewater:one part city water—were each pumped into an ecological treatment system. Influent and effluent water samples were analyzed for PO₄-P, TP, TN, NH₄-N, NO₃-N, total suspended solids (TSS), and carbonaceous biochemical oxygen demand (CBOD₅). Influent dairy wastewater volumetric loading rates were much greater than those of municipal wastewater. Regardless of influent wastewater strength, concentrations of all measured variables were significantly reduced between the influent and effluent of the ecological treatment system. At the lowest wastewater strength, PO₄-P was reduced 39%, TN 83%, and NH₄-N 89%, while at the highest wastewater strength, PO₄-P was reduced 41%, TN 79%, and NH₄-N 70%. Increased wastewater strength required greater aerobic treatment volume to reduce concentrations of NH₄-N and CBOD₅.     

Recovery of organic carbon and phosphorus from wastewater by Fe-enhanced primary sedimentation and sludge fermentation

A new chemically enhanced primary sedimentation (CEPS) and sludge fermentation process are developed for improved nutrient removal, energy saving and resource recovery in municipal wastewater treatment. The FeCl₃-based CEPS with a dosage of 20 mg-Fe/L can remove 75.6% of organic pollutants and 99.3% of PO₄-P on average from wastewater. Under natural fermentation conditions, the CEPS sludge undergoes effective hydrolysis and acidogenesis to produce volatile fatty acids (VFAs) and release phosphate as valuable resources. By using CEPS, around 27% of the organic carbon in wastewater influent can be recovered via sludge fermentation, mainly in the form of VFAs, and about 23% of phosphorus recovered for making vivianite fertilizer. In comparison, both the organic and phosphorus recovery ratios from wastewater are under 10% with conventional primary sedimentation and sludge fermentation. CEPS combined with side-stream sludge fermentation can be readily applied in new treatment plants or in a retrofit of existing treatment systems.     

Characterization of cell structural change,growth, lipid accumulation,and pigment profile of a novel oleaginous microalga, <Emphasis Type="Italic">Vischeria stellata</Emphasis> (Eustigmatophyceae), cultured with different initial nitrate supplies

The appropriate microalgal species and the optimal nitrogen supply in culture medium are vital factors in maximizing biomass and metabolite productivities in microalgae. Vischeria stellata is an edaphic unicellular eustigmatophycean microalga. Cytological and ultrastructural characteristics and the effects of different initial nitrate-nitrogen concentrations on growth, lipid accumulation, fatty acid profile, and pigment composition were investigated in the present study. The cell structures of V. stellata changed with the degree of nutrient utilization and growth phase. The initial nitrate concentration for the optimal growth of V. stellata ranged from 6.0 to 9.0 mM. The maximum total lipid (TLs), neutral lipid (NLs), and total fatty acid (TFAs) contents were 55.9, 51.9, and 44.7 % of dry biomass, respectively. The highest volumetric productivity of TLs, NLs, and TFAs reached 0.28, 0.25, and 0.21 g L^?1 day^?1, respectively. V. stellata had a suitable fatty acid profile for biodiesel production, as well as containing eicosapentaenoic acid (EPA) for nutraceutical applications. In addition, the content β-carotene, increased gradually as culture time was prolonged, resulting in its exclusive production at the end of cultivation. V. stellata is a promising microalgal strain for the production of biofuels and bioproducts.     

Phosphorus removal coupled to bioenergy production by three cyanobacterial isolates in a biofilm dynamic growth system

In the present study a closed incubator, designed for biofilm growth on artificial substrata, was used to grow three isolates of biofilm-forming heterocytous cyanobacteria using an artificial wastewater secondary effluent as the culture medium. We evaluated biofilm efficiency in removing phosphorus, by simulating biofilm-based tertiary wastewater treatment and coupled this process with biodiesel production from the developed biomass. The three strains were able to grow in the synthetic medium and remove phosphorus in percentages, between 6 and 43%, which varied between strains and also among each strain according to the biofilm growth phase. Calothrix sp. biofilm turned out to be a good candidate for tertiary treatment, showing phosphorus reducing capacity (during the exponential biofilm growth) at the regulatory level for the treated effluent water being discharged into natural water systems.

Besides phosphorus removal, the three cyanobacterial biofilms produced high quality lipids, whose profile showed promising chemical stability and combustion behavior. Further integration of the proposed processes could include the integration of oil extracted from these cyanobacterial biofilms with microalgal oil known for high monounsaturated fatty acids content, in order to enhance biodiesel cold flow characteristics.     

Low-cost cultivation of <Emphasis Type="Italic">Scenedesmus</Emphasis> sp. with filtered anaerobically digested piggery wastewater: biofuel production and pollutant remediation

A laboratory study was conducted on biomass and lipid production by Scenedesmus sp. and the removal of total nitrogen (TN) and total phosphorus (TP) from filtered anaerobically digested piggery wastewater. The dry weight (DW), lipid content and productivity, total nitrogen, and total phosphorus removal rate were assessed in five media: modified soil extract (MSE) medium, 5 % anaerobic digested wastewater (ADWW), 10 % ADWW, 15 % ADWW, and 5 % ADWW supplemented with NaNO₃. The highest biomass productivity appeared in the 15 % ADWW group, which was 20.4 % higher than MSE group. The highest lipid content was found in the 5 % ADWW group (31.60 %), while the highest lipid productivity was in the 10 % ADWW group (27.01 mg L^?1 day^?1). Compared with the 5 % ADWW group, the 5 % ADWW group supplemented with NaNO₃ had a similar biomass amount but lower lipid content and productivity. The fatty acids percentage of Scenedesmus sp. showed a slight difference in different media, but with the four dominant fatty acids (C16:0, C18:1, C18:2, C18:3) accounting for 87 % of the total fatty acids, suggests that Scenedesmus sp. in ADWW medium was no different than MSE in terms of lipid composition and content. TN removal rates were 82.85, 82.51, 85.85, 91.28, and 78.71 % in groups 1 to 5, and TP removal rates were 53.05, 88.53, 87.77, 88.72, and 80.64 %. Our experiment also shows the feasibility of using ADWW as a substitute of all the elements of MSE medium except for carbon, which would significantly reduce the costs of microalgal culture.     

Optimization of aeration for biodiesel production by <Emphasis Type="Italic">Scenedesmus obliquus</Emphasis> grown in municipal wastewater

Despite the significant breakthroughs in research on microalgae as a feedstock for biodiesel, its production cost is still much higher than that of fossil diesel. One possible solution to overcome this problem is to optimize algal growth and lipid production in wastewater. The present study examines the optimization of pretreatment of municipal wastewater and aeration conditions in order to enhance the lipid productivity of Scenedesmus obliquus. Results showed that no significant differences were recorded in lipid productivity of S. obliquus grown in primary settled or sterilized municipal wastewater; however, ultrasound pretreatment of wastewater significantly decreased the lipid production. Whereas, aeration rates of 0.2 vvm significantly increased lipid content by 51 %, with respect to the non-aerated culture, which resulted in maximum lipid productivity (32.5 mg L^?1 day^?1). Furthermore, aeration enrichment by 2 % CO₂ resulted in increase of lipid productivity by 46 % over the CO₂ non-enriched aerated culture. Fatty acid profile showed that optimized aeration significantly enhanced monounsaturated fatty acid production, composed mainly of C18:1, by 1.8 times over the non-aerated S. obliquus culture with insignificant changes in polyunsaturated fatty acid proportion; suggesting better biodiesel characteristics for the optimized culture.     

Novel application of oxygen-transferring membranes to improve anaerobic wastewater treatment

Anaerobic biological wastewater treatment has numerous advantages over conventional aerobic processes; anaerobic biotechnologies, however, still have a reputation for low-quality effluents and operational instabilities. In this study, anaerobic bioreactors were augmented with an oxygen-transferring membrane to improve treatment performance. Two anaerobic bioreactors were fed a synthetic high-strength wastewater (chemical oxygen demand, or COD, of 11,000 mg l(-1)) and concurrently operated until biomass concentrations and effluent quality stabilized. Membrane aeration was then initiated in one of these bioreactors, leading to substantially improved COD removal efficiency (> 95%) compared to the unaerated control bioreactor (approximately 65%). The membrane-augmented anaerobic bioreactor required substantially less base addition to maintain circumneutral pH and exhibited 75% lower volatile fatty acid concentrations compared to the unaerated control bioreactor. The membrane-aerated bioreactor, however, failed to improve nitrogenous removal efficiency and produced 80% less biogas than the control bioreactor. A third membrane-augmented anaerobic bioreactor was operated to investigate the impact of start-up procedure on nitrogenous pollutant removal. In this bioreactor, excellent COD (>90%) and nitrogenous (>95%) pollutant removal efficiencies were observed at an intermediate COD concentration (5,500 mg l(-1)). Once the organic content of the influent wastewater was increased to full strength (COD = 11,000 mg l(-1)), however, nitrogenous pollutant removal stopped. This research demonstrates that partial aeration of anaerobic bioreactors using oxygen-transferring membranes is a novel approach to improve treatment performance. Additional research, however, is needed to optimize membrane surface area versus the organic loading rate to achieve the desired effluent quality.     

Effect of alginate structure and microalgae immobilization method on orthophosphate removal from wastewater

Microalgae play an important role during the tertiary treatment of municipal wastewater. Cell immobilization techniques have been developed in order to improve the quality of the treated wastewater and avoid wash out of the biomass. Since cell immobilization method may affect the nutrient removal efficiency, ten strains of microalgae were immobilized in sodium alginate gel in different-diameter circular screens, and orthophosphate removal efficiency from municipal wastewater was studied. Results indicate that the alginate immobilization screen size and contact surface with wastewater affects the microalgae synthesis activity and thus orthophosphate removal efficiency. Increasing the contact surface by making smaller alginate screens will increase the cation exchange rate and reduce the orthophosphate concentration in the medium. Among all microalgae treatments, Scenedesmus rubescens MCCS 018, Chlamydomonas sp. MCCS 026, and Chroococcus dispersus MCCS 006 had the highest PO ₄ ^3- -P removal efficiency of 68.8%, 71.9%, and 72.3% within 12?days.     

Efficacy of Chlorella pyrenoidosa and Scenedesmus abundans for Nutrient Removal in Rice Mill Effluent (Paddy Soaked Water)

Microalgae are product of sustainable development owing to its ability to treat variety of wastewater effluents and thus produced biomass can serve as value added product for various commercial applications. This paper deals with the cultivation of microalgae species namely Chlorella pyrenoidosa and Scenedesmus abundans in rice mill effluent (i.e., paddy soaked water) for nutrient removal. In order to investigate the nutrient removal capability, microalgae are subjected to cultivation in both raw and autoclaved samples. The maximum phosphate removal by Scenedesmus abundans and Chlorella pyrenoidosa in raw sample was 98.3% and 97.6%, respectively, whereas, the removal of ammoniacal nitrogen by Scenedesmus abundans and Chlorella pyrenoidosa in raw sample was 92% and 90.3%, respectively. The growth (measured in terms of chlorophyll content) of Scenedesmus abundans and Chlorella pyrenoidosa in raw sample was 3.88 mg/l and 5.55 mg/l, respectively. The results indicate the suitability of microalgae cultivation in rice mill effluent treatment for nutrient removal.     

Advanced treatment of high-strength wastewater by a submerged bio-film process

A submerged bio-film process was studied as a tertiary treatment to decrease the BOD of secondary effluent from a combined chemical-biological treatment of high-strength wastewater to below the permitted limit (30 mg/l) for waste facilities in Japan. The operational conditions to keep the final effluent below 30 mg/l of BOD were as follows: the influent BOD to the bio-film tank should be under 300 mg/l and a BOD-surface loading should be below 2 g/m²/d. The influent pH of 9.0–12.5 did not affect the treatment efficiency unfavorably. Acclimation is the compensating factor for variations of pH in this process. Removal rates of suspended solids were not influenced by BOD-surface loading. The calculated BOD removal coefficient was 2.57 × 10⁻⁵ when the influent BOD was below 300 mg/l.     

Seasonal variation in light utilisation,biomass production and nutrient removal by wastewater microalgae in a full-scale high-rate algal pond

There has been renewed interest in the combined use of high-rate algal ponds (HRAP) for wastewater treatment and biofuel production. Successful wastewater treatment requires year-round efficient nutrient removal while high microalgal biomass yields are required to make biofuel production cost-effective. This paper investigates the year-round performance of microalgae in a 5-ha demonstration HRAP system treating primary settled wastewater in Christchurch, New Zealand. Microalgal performance was measured in terms of biomass production, nutrient removal efficiency, light absorption and photosynthetic potential on seasonal timescales. Retention time-corrected microalgal biomass (chlorophyll a) varied seasonally, being lowest in autumn and winter (287 and 364 mg m^?3day^?1, respectively) and highest in summer (703 mg m^?3day^?1), while the conversion efficiency of light to biomass was greatest in winter (0.39 mg Chl- a per μmol) and lowest in early summer (0.08 mg Chl- a per μmol). The percentage of ammonium (NH₄–N) removed was highest in spring (79 %) and summer (77 %) and lowest in autumn (47 %) and winter (53 %), while the efficiency of NH₄–N removal per unit biomass was highest in autumn and summer and lowest in winter and spring. Chlorophyll-specific light absorption per unit biomass decreased as total chlorophyll increased, partially due to the package effect, particularly in summer. The proportional increase in the maximum electron transport rate from winter to summer was significantly lower than the proportional increase in the mean light intensity of the water column. We concluded that microalgal growth and nutrient assimilation was constrained in spring and summer and carbon limitation may be the likely cause.     

Phycoremediation resultant lipid production and antioxidant changes in green microalgae Chlorella Sp.

In this investigation, we report on the treatment of tannery wastewater using microalgae Chlorella species to produce lipid and fatty acid as well as changes in antioxidant metabolism during the treatment. The variation in growth, production of pigments, antioxidant metabolism, lipid and fatty acids, and nutrient removal from wastewater during the remediation were observed. Surprisingly, a profuse growth was found in 50% diluted tannery wastewater (TW), which supported to accumulate high yield of lipid (18.5%) and unsaturated fatty acids (50.05%). The antioxidant activity of microalgae in both the concentrations (50% and 100% TW) were viz., lipid peroxidation 1.6 ± 0.1 and 2.3 ± 0.02nmol MDA mg^?1 protein, SOD 10.3 ± 0.4 and 15.7 ± 0.9 U mg^?1 protein, CAT 0.17 ± 0.036 and 0.52 ± 0.06 U mg^?1 protein, and APX 7.2 ± 0.8 and 11.2 ± 09 U mg^?1 protein respectively, which point out that the free radical scavenging mechanism against heavy metal stress. Maximum phycoremediation of heavy metals observed from both concentrations during the healthy growth period were Cr – 73.1, 45.7%, Cu – 90.4, 78.1%, Pb – 92.1, 52.2%, and Zn – 81.2, 44.6%, respectively. This study proved the potential use of Chlorella for heavy metal and nutrient removal from tannery wastewater. Moreover, an unaffected growth with high antioxidant activity of this species promises a sustainable lipid and fatty acid contents for biofuel production.     

Phycoremediation of municipal wastewater by microalgae to produce biofuel

Municipal wastewater (WW), if not properly remediated, poses a threat to the environment and human health by carrying significant loads of nutrients and pathogens. These contaminants pollute rivers, lakes, and natural reservoirs where they cause eutrophication and pathogen-mediated diseases. However, the high nutrient content of WW makes it an ideal environment for remediation with microalgae that require high nutrient concentrations for growth and are not susceptible to toxins and pathogens. Given that an appropriate algal strain is used for remediation, the incurred biomass can be refined for the production of biofuel. Four microalgal species (Chlamydomonas reinhardtii, Chlorella sp., Parachlorella kessleri-I, and Nannochloropsis gaditana) were screened for efficient phycoremediation of municipal WW and potential use for biodiesel production. Among the four strains tested, P. kessleri-I showed the highest growth rate and biomass production in 100% WW. It efficiently removed all major nutrients with a removal rate of up to 98% for phosphate after 10 days of growth in 100% municipal WW collected from Delhi. The growth of P. kessleri-I in WW resulted in a 50% increase of biomass and a 115% increase of lipid yield in comparison to growth in control media. The Fatty acid methyl ester (FAME), and fuel properties of lipids isolated from cells grown in WW complied with international standards. The present study provides evidence that the green alga P. kessleri-I effectively remediates municipal WW and can be used to produce biodiesel.     

Methods for the recovery, isolation and detection of Cryptosporidium oocysts in wastewaters

This correspondence describes the successful development of methods for the recovery, isolation and detection of Cryptosporidium oocysts in wastewater and biosolids. Wastewater from one plant was used to optimize methods in raw influent as well as primary, secondary and tertiary effluents. Raw influents and primary effluents were concentrated using centrifugation followed by isolation of Cryptosporidium oocysts using immunomagnetic separation (IMS) and detection of recovered organisms using epifluorescence microscopy. Mean oocyst recovery in raw influent was 29.2+/-12.8% and 38.8+/-27.9% in primary effluent at three sample volumes tested. Secondary and tertiary effluents were analyzed using a modified Method 1622 resulting in mean oocyst recoveries of 53.0+/-19.2% and 67.8+/-4.4%, respectively. In biosolids with approximately 10% total solids, mean oocyst recovery was 43.9+/-10.1% using IMS with a 5 g (wet weight) sample size. Due to the variability in these matrices, an internal microbiological standard was incorporated to serve as a tool for method performance.