Culturing microalgae for nutrients removal from wastewater (review)

Summary

Research works in the field of microalgae culturing with the use of wastewater as substrate have gained ground overseas. In this way the removal of nutrients used for biomass growth as well as of some heavy metals and other pollutants is provided. A description of process flow schemes of wastewater treatment combined with microalgae culturing and basic indicators of wastewater treatment facilities operation is presented. Three options of retrofitting a microalgae culturing plot are considered: at the end of the process flow scheme for enhanced nutrients removal from wastewater and biomass production as a raw material for biofuel; at the beginning of the process flow scheme with possible utilization of both nutrients for microalgae culturing and organic carbon that improves the biomass output; the scheme that provides for feeding only nutrient enriched solution from dewatering aerobically digested sludge are considered. Microalgae can be a valuable raw material for production of biofuel, food supplements, fertilizers, soil conditioners and adsorbents. However, for the implementation of such schemes large production areas are required, therefore their use is expedient for small-scale treatment facilities or facilities located in small towns or rural areas. Beside that a solution for some technological problems is required. The keen interest in the research in this field in different countries shows that the wastewater treatment technology with the use of culturing microalgae is an upcoming trend for experts.

Key words

wastewater , nutrients removal , biomass , microalgae culturing , biodiesel fuel

The key results of the full-scale studies of sludge digestion technology with biomass recycle

Summary

For a number of years the specialists of R&D Centre of «Mosvodokanal» JSC have been developing and testing in a lab environment the technologies that can enhance the process of wastewater sludge digestion within the existing capacity of the treatment facilities. As a result a method was chosen which provided for thickening a part of sludge with subsequent thickened sludge returning back into the digester. The important advantage of this method is the possibility of increasing sludge retention time as dry matter without increasing the hydraulic retention time with simultaneous biomass retaining. Therefore, the required decomposition rate is provided in smaller size reactors. In the course of studying the process solutions on wastewater sludge digestion optimization the method of biomass recycle showed itself as the most economically viable. During the full-scale studies of the recycle option the decomposition of the ash-free basis increased in average to 56.6% (42.2% reference value) which was confirmed by the significant improvement of sludge dewatering properties. The average biogas yield increased by 3%. In the course of the experimental studies no adverse effects of the sludge recycling technology on the digester performance were observed. The results obtained during the full-scale studies evidence the long-term benefits of introducing the technology of wastewater sludge digestion with biomass recycle at the Moscow wastewater treatment facilities.

Key words

anaerobic fermentation , methane tank , decomposition of organic matter , biomass , sludge thickening , recycle

Improving the efficiency of wastewater sludge treatment process with the use of a biogas unit

Summary

The design of a biogas unit for conducting scientific experiments and training at the basic Department of «Engineering Systems of Housing and Public Utilities» affiliated with MUE «Izhvodokanal» is presented. The results of the experimental studies carried out in 2014 and 2023 focused on producing biogas in a biogas unit are presented. The method for conducting experimental studies is given taking into account the achieved results of the previously conducted experiments focused on producing the maximum volume of generated biogas and potting soil from processed wastewater sludge. The results of other experimental studies during practical training (research work of graduate students) in 2023 are presented. The efficiency of using the biogas unit at the wastewater treatment facilities operated by the water utilities of the Udmurt Republic and enterprises of the agro-industrial complex is stipulated.

Key words

anaerobic fermentation , wastewater sludges , biomass , biogas unit , energy efficient technologies