Wastewater Substrate Disinfection for Application of Synechococcus Elongatus PCC 7942 Cultivation as Tertiary Treatment

The cultivation of microalgae or/and cyanobacteria in nutrient-rich wastewaters presents a significant opportunity for enhancing sustainability of tertiary wastewater treatment processes via resources/energy recovery/production. However, maintaining a monoculture in wastewater-media constitutes a significant challenge to be addressed, as a plethora of antagonistic and predating microorganisms exist is such media. In this regard, the present work assesses the efficiency of the low-cost wastewater substrate disinfection techniques of filtration, use of NaClO, H2O2 or Fe(VI), in terms of antagonistic or/and predating microbial species growth inhibition in Synechococcus elongatus PCC 7942 cultivations. Nitrates and phosphates removal rates were also experimentally assessed. The results showed that filter thickness has a greater effect on disinfection efficiency than that of filter’s pore size. Furthermore, the disinfection efficiency of Fe(VI), which was produced on-site by electrosynthesis via a Fe0/Fe0 cell, was greater than that of NaClO and H2O2. Filtration at ≤ 1.2 µm pore size coupled with chemical disinfection leads to unhindered S7942 growth and efficient nitrates and phosphates removal rates, at dosages of CT ≥ 270 mg min L−1 for NaClO and CT ≥ 157 mg min L−1 for Fe(VI). The coagulation action of Fe(III) species that result from Fe(VI) reduction and the oxidation action of Fe(VI) can assist in turbidity, organic compounds and phosphorous removal from wastewater-media. Moreover, the residual iron species can assist in S7942 harvesting and may enhance photosynthesis rate. Thus, the utilization of wastewaters for S7942 cultivation as tertiary treatment seems a promising and novel alternative to common nutrient removal processes that can reduce environmental footprint and operational costs of wastewater treatment plants.

Tertiary Treatment for Safely Treated Wastewater Reuse

The tertiary treatment of resulting water from a conventional biological treatment process is envisaged in the aim to obtain a high quality of water that can be reused for different purposes. This treatment is based on the integration of the membrane-based technologies in the total process of wastewater treatment. The experimental studies are carried out on a small pilot, equipped with different mineral membranes of micro and ultrafiltration. These membranes are used for the different tested processes (MF, MF-UF and cogulation-MF). The results obtained make it possible to attend a complete elimination of the total flora and an additional reduction of the other parameters such as turbidity, suspended matter, COD and BOD. Tests on a large scale are then carried out on a semi-industrial pilot, equipped with the same type of membranes. The optimization of the operating conditions made allow the obtaining under the conditions of transmembrane pressure 0.85 bar, a cross flow velocity of 2.25m/s and with ambient temperature a filtrate flux of about 200 L/hm 2. The coupling of a stage of coagulation in the membrane process allows the reduction of the effect of the membrane fouling and an improvement of 36% of the filtrate flux.

Experience in using phyto-structures for tertiary treatment of urban wastewater

This paper considers the experimental biocenosis development for tertiary wastewater treatment with respect to the climate features of South of Russia. The plant species with advantaged biotechnical characteristics that acceptable for steppe environment are described. The growing season productivity of the highest aquatic vegetation for the phyto-structures first year exploitation is determined. The quantitative statistics for indicative microorganism populations is calculated. The data obtained allows to measure the ecological effectiveness of wastewater treating phyto-system and to develop a cheap and recyclable biocenosis for the inhabited localities with temperate continental climate.

Prevalence of common enteric viruses in municipal wastewater treatment plants and their health risks arising from wastewater reuse

Enteric viruses are known to be prevalent in municipal wastewater, but information on the health risks arising from wastewater reuse is limited. This study quantified six common enteric viruses in raw wastewater and determined the effectiveness of different secondary and tertiary treatment processes at reducing their abundances in three full-scale wastewater treatment plants in China. In the raw wastewater, polyomavirus BK and norovirus GII (Nov GII) exhibited the highest abundance among the detected DNA and RNA viruses, respectively, with concentrations >5 log10 copies/L. Viruses in the raw wastewater were mainly removed by the secondary treatment processes, with log reduction values ranging from 1 to 2. The tertiary treatment processes of both chlorination and ultraviolet irradiation facilitated the additional reduction of viruses. The quantitative microbial risk assessment was applied to estimate the health risks of adenovirus (Adv) and Nov GII when reusing the treated wastewater for irrigation of public green spaces and crops. Estimated disabled-adjusted life-years of Adv and Nov GII for both reuses were higher than the risk threshold (10−6) required by the WHO in the actual scenarios. More effective treatment technologies should be implemented to remove viruses for safe reuse of the treated wastewater.