Query: microalgaes for treatment of wastewater

title: Bioremediation of textile wastewater and successive biodiesel production using microalgae
abstract: Microalgal biodiesel has emerged as an environment friendly alternative to the existing fossil fuels. The commercial production of this biodiesel is still challenging due to several technical and economic issues, which span from mass cultivation of microalgae to the biodiesel production. Mass cultivation is the most critical step in terms of water and nutrient requirement. Industrial wastewater such as textile wastewater (TWW) is a cheap source for water, which additionally contains necessary nutrients (phosphate, nitrates, micronutrients etc. and organic dyes (potential carbon source) for algae cultivation. The application of microalgae for biodiesel production employing single objective strategy is not sustainable. Microalgae can be effectively employed to bioremediate TWW (dyes and nutrients removal) and to produce biodiesel from grown microalgae. This process integration (bioremediation biodiesel production) can potentially improve biodiesel production and wastewater treatment. However, this process coupling needs to be thoroughly investigated to identify and optimize critical process factors (algal species, cultivation and harvesting methods, bioremediation mechanism etc. This study has reviewed the status of TWW as potential source of water and nutrients, role of different algal species in the bioremediation of TWW, different cultivation systems, harvesting and biodiesel production methods. This review also suggests future research and development challenges for coupled textile wastewater treatment and microalgal biodiesel production.

title: Microalgae and Wastewater Treatment: Advantages and Disadvantages
abstract: Wastewater generation has concomitantly increased with the growth of world human population in the last century. The uncontrolled discharge of wastewater may result in serious social, environmental and health problems. At the same time, the use of microalgal based systems has been widely studied for a variety of residual effluents treatment since the early 1950s. In this context, different technologies have been developed, and new strategies to cope with specific needs have been investigated worldwide. There are several advantages of microalgal based systems compared to traditional wastewater treatment technologies, namely, (1) pollutants and pathogen decrease, (2) nutrient recovery in the form of valuable biomass, (3) energy savings and (4) CO2 emissions reduction. In spite of all these advantages, there are still many challenges to overcome before attaining the real implementation of this technology. Those challenges include (1) land requirement, (2) effect of wastewater characteristics, (3) environmental and operational condition influence and (4) biomass harvesting and valorization. This chapter will explore and discuss the main advantages and limitations of using this green technology for wastewater treatment based on our expertise and the latest insights on this topic.

title: Microalgae based wastewater treatment for nutrients recovery: A review.
abstract: The water resource crisis and concerns with environmental pollution are pushing for upgrading of conventional wastewater treatment process. Microalgae based wastewater treatment process has shown many advantages that can meet the new demand for improved wastewater treatment. However, considering the issues related to the complexity of wastewater characteristics and adaptability of microalgae species, and the challenges to the design and optimization of treatment processes in order to achieve higher removal efficiencies with lower costs, further exploration and research are still needed. This review provides an overview of microalgae strains commonly used for wastewater treatment, physical and chemical properties of various wastewaters and their suitability for algae cultivation, factors affecting algae growth, nutrient assimilation/removal and biomass productivity. The design and operation of microalgae based wastewater treatment processes are also discussed. Moreover, the issues and limitations of microalgae based wastewater treatment are also discussed and suggestions are proposed for the further research and development.

title: Energetic evaluation of wastewater treatment using microalgae, Chlorella vulgaris
abstract: This research evaluates the feasibility of utilizing municipal wastewater source as growth medium for microalgae production and wastewater treatment. First, the effect of the addition of external organic carbon on the microalgae growth and wastewater treatment was studied. Second, actual municipal wastewater from two different (primary and secondary) levels of treatment of an oxidation ditch wastewater treatment plant was used as a growth medium to evaluate both the microalgae growth and wastewater treatment. Third, the effect of light under day/night cycles was evaluated using actual municipal wastewater. A comparative analysis of volumetric biomass productivities, specific growth rates and energetic evaluation of the three different experimental conditions was performed. COD removal rates were 37.5 mg/L, 87.5 mg/L, and 118.75 mg/L per day while microalgae volumetric biomass concentrations were approximately 50 80 mg/L per day with specific biomass growth rates of 0.81, 0.89, and 1.28 1/d for 125, 250, and 500 mg/L COD concentrations, respectively. COD removal, biomass production and specific growth rates are lower for the municipal wastewater due to poor availability of carbon source. However, microalgae present a promising alternative when the energetic evaluation is considered for both actual and synthetic wastewater treatment. A total of 13.5, 17.4, and 35.2% of net energy recovery was possible with microalgae harvested in synthetic wastewater at 125, 250, and 500 mg/L COD concentrations, respectively while a total of 4.7% net energy recovery was possible with microalgae harvested in raw wastewater after accounting for the energy required for wastewater treatment.

title: Utilization of Microalgae in Aquaculture System: Biological Wastewater Treatment
abstract: We recently developed an autotrophic biofloc technology (ABFT) system entailing simultaneous microalgae co culturing with juvenile farming stage fish and shrimp in aquaculture and microalgae based water treatment. The present study was conducted to confirm the potentialities of the ABFT system at the remaining stages (seedling to adult farming, Nile tilapia) for industrial level implementation. In the results at the seedling stage, an excellent water purification effect and significant water conservation (97% reduction) by microalgae were verified. Indeed, among the fish, there were not any significant differences, either in growth performance or in body composition, and the wastewater from this system was recycled by use for the growth of various plants. Further, the ABFT system was demonstrated to have a positive effect on production economics by simplifying the production process steps (simultaneous fish breeding and wastewater treatment) and providing for a natural hatching environment. In summary, the ABFT system can be integrated with existing systems on an industrial level as an effective and efficient means of achieving sustainable aquaculture.

title: Microalgae cultivation for wastewater treatment and biogas production at Moscow wastewater treatment plant.
abstract: The process of cultivation of microalgae on purified and clarified wastewater of Kuryanovo wastewater treatment plants (KWWTP) was studied. The studies were conducted on monoculture (Scenedesmus quadricauda and Chlorella sorokiniana) and on polyculture, the composition of which was formed from microalgae present in the wastewater. The authors created and investigated the columnar photobioreactor (PBR) which acted as a pilot project on the purified and clarified water of KWWTP and allowed the removal of total nitrogen and phosphorus phosphates with an efficiency of up to 90% The formation of a stable biocenosis from 22 species of algae (with 3 4 dominant species) and 31 species of zooplankton organisms belonging to six systematic subdivisions was recorded. The optimal retention time of the microalgae polyculture for the most effective wastewater treatment has been determined. The conducted studies have shown that the depth of decomposition of ashless matter and the ultimate biogas potential of untreated microalgae biomass is 15% lower than the corresponding values obtained with digestion of activated sludge, which necessitates studies in the field of pretreatment of algal biomass. The paper shows: connections between chlorophyll a content, algal biomass and fluorescence index F0 and between biomass increment and Fv/Fm value.

title: Harvesting and pre treatment of microalgae cultivated in wastewater for biodiesel production: A review
abstract: Cultivation of microalgae using wastewater has received considerable attention around the globe as a platform to remove inorganic nutrients from the wastewater and producing microalgae biomass for biodiesel production. This can be done by converting freely available nutrients from the wastewater (particularly nitrogen, N and phosphorus, P) into microalgae biomass with concomitant carbon dioxide (CO 2 sequestration via photosynthesis process. In fact, microalgae biodiesel could help to reduce greenhouse gas (GHG) emissions to the atmosphere through the replacement of fossil diesel as it is made from renewable resources. Despite the various benefits to produce microalgae biodiesel, a number of technical hurdles such as complex processes, requirement of high energy input during cultivation and dewatering (harvesting steps) need to be addressed for commercialization purpose. Besides, additional pre treatment step is necessary to disrupt the microalgae cell wall to enhance lipid extraction efficiency. Hence, this paper is aims to reveal in depth analysis and discussions on the process of microalgae based wastewater treatment as well as microalgae cells disruption technology for lipid extraction. The paper also includes several new directions for technological improvements to improve commercialization potential of microalgae biodiesel.

title: Non sterile heterotrophic cultivation of native wastewater yeast and microalgae for integrated municipal wastewater treatment and bioethanol production
abstract: Currently over 80% of wastewater generated globally, is discharged into surface waters without adequate treatment. Major environmental and public health risks associated with such releases are particularly prevalent in developing countries where the infrastructure and financing for effective treatment is lacking. Novel low cost integrated wastewater treatment and biorefinery processes could provide a sustainable solution. This study investigated, for the first time, the feasibility of simultaneous wastewater treatment and bioethanol production in non sterile, heterotrophic bioreactors using either microalgae, wild yeast, or a co culture of microalgae and wild yeast. Scenedesmus sp. are known to achieve high biomass concentrations under sterile heterotrophic conditions. However, under the non sterile conditions proposed, relatively low nutrient removal rates (60% nitrate, 53% total ammonia nitrogen (TAN) and 46% orthophosphate) and biomass yields (0.98 0.10 g/L) were achieved. Wastewater grown microalgae and yeast co cultures achieved high nutrient removal rates (96% nitrate, 100% TAN and 93% orthophosphate) Wastewater grown yeast cultures produced consistently promising results, achieving high biomass concentrations of 3.7 0.1 and 4.2 0.1 g/L along with 100% nitrate, 100% TAN and 92.6% orthophosphate removal. Yeast provided the additional advantage of aerobic fermentation, possibly allowing integrated wastewater treatment and bioethanol production.

title: Analysis of a photobioreactor scaling up for tertiary wastewater treatment: denitrification, phosphorus removal, and microalgae production.
abstract: The present work studies the removal of nutrients (nitrate and phosphate) from a synthetic wastewater simulating a secondary treatment effluent using the microalgae Chlorella vulgaris in autotrophic photobioreactors, together with an analysis of the critical points affecting the scaling up process from laboratory to pilot scale. Laboratory experiments were done in open agitated 1 L photobioreactors under batch operation mode, while pilot scale experiments were done using a 150 L closed tubular photobioreactor under continuous operation mode. In both scales, nitrate was the limiting substrate and the effect of its concentration on microalgae performance was studied. From laboratory experiments, an average microalgae productivity of 85 mgVSS L 1 day 1 and approximate maximum N NO3 and P PO43 removal rates of 8 mg N gVSS 1 day 1, and 2.6 mg P gVSS 1 day 1 were found. Regarding pilot scale, the average microalgae productivity slightly decreased (76 mgVSS L 1 day 1) while the approximate maximum N NO3 and P PO43 removal rates slightly were increased (11.7 mg N gVSS 1 day 1 and 3.04 mg P gVSS 1 day 1) with respect to the laboratory scale results. The pilot scale operation worked under lower levels of turbulence and higher dissolved oxygen concentration and light intensity than laboratory experiments; those parameters were difficult to control and they can be identified as the critical points in the differences found on both nutrient removal and microalgae production.

title: Microalgae Brewery Wastewater Treatment: Potentials, Benefits and the Challenges
abstract: Concerns about environmental safety have led to strict regulations on the discharge of final brewery effluents into water bodies. Brewery wastewater contains huge amounts of organic compounds that can cause environmental pollution. The microalgae wastewater treatment method is an emerging environmentally friendly biotechnological process. Microalgae grow well in nutrient rich wastewater by absorbing organic nutrients and converting them into useful biomass. The harvested biomass can be used as animal feed, biofertilizer, and an alternative energy source for biodiesel production. This review discusses conventional and current brewery wastewater treatment methods, and the application and potential of microalgae in brewery wastewater treatment. The study also discusses the benefits as well as challenges associated with microalgae brewery and other industrial wastewater treatments.