Members of the University of Turku, with participation of their colleagues at the Faculty of Biology of the Lomonosov Moscow State University, have proved that under Nordic conditions wastewaters could be treated with the help of microalgae, while algal biomass is suitable for processing into biofuel. The scientists have presented the optimized technique for the removal from wastewater of organic compounds, along with nitrogen and phosphorus in the article, published in the Algal Research. The research has been supported by the Russian Science Foundation and conducted within the framework of the "Noah's ark" project (Microorganisms and Fungi Division).
People established algal ponds for wastewater treatment since ancient times. It was especially popular in the countries, which have ample solar energy but lack stationary treatment facilities. In India, algae ponds are used for community wastewater treatment but no one knows precisely when they emerged. William Oswald, the pioneer of algal biotreatment of wastewater, developed a solid scientific foundation for this technique more than 50 years ago. Over the last decade, the "green" wastewater treatment technologies attracted a considerable attention resulting in dozens of academic papers on this topic published yearly.
Scientists distinguish two types of microalgal cultivation systems: open (ponds, lagoons and so on) and closed (photobioreactors). Due to the technical complexity and high cost, the photobioreactors were not considered for wastewater treatment since, let alone the cost of maintenance of optimal temperature for microalgae growth in the photobioreactor. The Russian biologists together with their colleagues from the University of Turku (Finland) carried out pioneering research on optimization of photobioreactor-based method under Nordic conditions.
Photobioreactors are closed vessels harboring microalgae cell suspension, where required conditions are maintained. Such parameters like uniform illumination, constant temperature and concentration of carbon dioxide, oxygen and nutritional chemicals provide the necessary environment. Constant stirring if also required, moreover the suspension should be stirred at such speed, which provides the absence of cell sedimentation. Photobioreactors differ in form and construction: they could be plate, tubular or helical.
The efficiency of wastewater treatment efficiency is checked is checked by specialists in the outflow of the photobiotreactor. There are two efficiency characteristics: the pollutant removal completeness and its rate -- the retention time, during which pollutant concentration in the treated water falls to the level acceptable for discharge (maximum permissible concentration -- MPC).
The scientists have used Chlorella vulgaris UHCC0027 -- a microalgal strain, isolated in southwestern Finland, its natural habitat. Photobioreactors with such algae could be operated without additional heating since all biological processes effectively proceed inside the system under ambient temperature. This is the main outcome of the research.
Alexei Solovchenko, Doctor of Biology and one of the research participants, says: "The guiding principle applied for obtaining and choosing strains for biotreatment purposes, is very simple. The most promising organisms are often isolated from the treatment facilities and surrounding territories. It was curious that an alga from the Nordic collection has proved worth in the process of research. However, an indigenious algal community from the same wastewaters eventually matched the algal monoculture in the efficiency of treatment.
Moreover, microalgal biomass, growing in wastewaters, has proved to be suitable for conversion into biodiesel with minimum amendment (blending with fossil diesel fuel and doping). Basing on the achieved knowledge, one could design more advanced biotechnologies for wastewater treatment and biofuel production under Nordic conditions.
Judging from the author's words, businesses are interested in the novel tool for wastewater treatment. Alexei Solovchenko shares: "Business considers algal biotreatment very promising. For instance, our project has been done on the basis of a Finnish commercial firm, professionally dealing with wastewater treatment. Its members also took part in our work. What is important is that we've achieved rather fair results, using pure municipal wastewater, taken from the Turku network and not from model environments, applied in most researches."