Primacy of ecological engineering tools for combating eutrophication: An ecohydrological assessment pathway

Effective microorganism water treatment method for rapid eutrophic reservoir restoration

Since reservoirs perform many important functions, they are exposed to various types of unfavorable phenomena, e.g., eutrophication which leads to a rapid growth of algae (blooms) that degrade water quality. One of the solutions to combat phytoplankton blooms are effective microorganisms (EM). The study aims to evaluate the potential of EM in improving the water quality of the Turawa reservoir on the Mała Panew River in Poland. It is one of the first studies providing insights into the effectiveness of using EM in the bioremediation of water in a eutrophic reservoir. Samples for the study were collected in 2019-2021. The analysis showed that EM could be one of the most effective methods for cleaning water from unfavorable microorganisms (HBN22, HBN36, CBN, FCBN, FEN) - after the application of EM, a reduction in their concentration was observed (from 46.44 to 58.38% on average). The duration of their effect ranged from 17.6 to 34.1 days. The application of EM improved the trophic status of the Turawa reservoir, expressed by the Carlson index, by 7.78%. As shown in the literature review, the use of other methods of water purification (e.g., constructed wetlands, floating beds, or intermittent aeration) leads to an increase in the effectiveness and a prolongation of the duration of the EM action. The findings of the study might serve as a guide for the restoration of eutrophic reservoirs by supporting sustainable management of water resources. Nevertheless, further research should be conducted on the effectiveness of EM and their application in the remediation of eutrophic water reservoirs.

Spatio-temporal evolution of eutrophication and water quality in the Turawa dam reservoir, Poland

The objectives of the article are: to assess spatio-temporal evolution of eutrophication and water quality of the Turawa dam reservoir, located in south-western Poland on the Mała Panew River; to identify location and relationship between potential sources of physicochemical pollution related to the progressing process of eutrophication; and to determine trophic status and water quality indices of the selected research object. The analysis (Mann-Whitney U test, PCA, HCA, Spearman correlation matrix) showed a high susceptibility of the reservoir to eutrophication processes, especially due to the influence of dangerous loads of compounds emerging from areas with high tourist intensity and pollutants flowing from the Mała Panew River. The parameters deteriorating the ecological status were TP, DO, BOD₅, and COD. Considering the cumulative results of water quality indices for the period 1998-2020, the average water quality was in classes II or III. A noticeable deterioration appeared in water quality for the years 2016-2020, which proves the progressing eutrophication in the Turawa reservoir. In 1998-2020, the reservoir was classified as eutrophic or mesoeutrophic based on the calculated three trophic status indices. This article would help in developing a strategy for dealing with water blooms, a reliable system for monitoring pressures causing eutrophication, and optimal technologies for the reconstruction of multifunctional reservoirs.

Fast Capture and Efficient Removal of Bloom Algae Based on Improved Dielectrophoresis Process

A dielectrophoresis (DEP) method for direct capture and fast removal of Anabaena was established in this work. The factors affecting the removal efficiency of Anabaena were investigated systematically, leading to optimized experimental conditions and improved DEP process equipment. The experimental results showed that our improved DEP method could directly capture Anabaena in eutrophic water with much enhanced removal efficiency of Anabaena from high-concentration algal bloom-eutrophication-simulated solution. The removal rate could increase by more than 20% after applying DEP at 15 V compared with a pure filtration process. Moreover, the removal rate could increase from 38.76% to 80.18% in optimized experimental conditions (the initial concentration of 615 μg/L, a flow rate of 0.168 L/h, an AC voltage of 15 V, and frequency of 100 kHz). Optical microscopic images showed that the structure of the captured algae cells was intact, indicating that the DEP method could avoid the secondary pollution caused by the addition of reagents and the release of phycotoxins, providing a new practical method for emergent treatment of water bloom outbreaks.

Remediation of PO43− in Water Using Biodegradable Materials Embedded with Lanthanum Oxide Nanoparticles

Eutrophication, a process in which algae grow inordinately, adversely affects aqueous fauna. Phosphorous at levels above 0.1 mg/L is adequate to cause eutrophication. In this study, we aimed to reduce the amount of PO43− in water using biodegradable and ecofriendly sorbents. Lanthanum oxide nanoparticles were doped in agar and cellulose sponge to produce two new sorbents, agar–La and sponge–La, respectively. Both sorbents showed high efficacy in remediating up to 10 mg/L PO43− in water. Sponge–La was found to be more proficient in terms of adsorption than agar–La because it required just 1 h to achieve 80% adsorption when the initial concentration of PO43− was 10 mg/L. Sponge–La was effective at pH levels ranging from 4 to 8, with a removal rate of 80–100%. Although agar–La displayed a slow sorption process, it presented a high adsorption capacity (156 mg/g); moreover, the cake-shaped agar–La could be easily manufactured and separated from an aqueous matrix or any water-based solutions. These two sorbents could effectively remove high concentrations of PO43−, and their preparation requires a simple step. Agar–La was easier to manufacture, whereas the adsorption process using sponge–La was more rapid. In addition, both sorbents can be easily separated from the matrix after sorption.

Eco-bioengineering tools in ecohydrological assessment of eutrophic water bodies

Eutrophication of water bodies and deterioration of water quality are emerging environmental crises. The root causes and consequences of eutrophication are multidirectional. Thus, they provide a huge scope of risk-analysis and risk-assessment in the domain of remediation studies. However, recent restoration studies reveal a global trend of utilizing traditional restoration methods combined with advanced pioneer innovative techniques developed in the field of science and technology. This review introduces a novel approach to consider ecohydrological assessment of eutrophication by classical biomanipulation practices emphasising on their evolution into innovative 'eco-bioengineering' methods. The main objective of this study is to critically analyse and recognize the research gaps in classical biomanipulation and appreciate the reproducibility and efficacy of eco-bioengineering methods at micro- and macrolevel aquatic ecosystems. Comprehensive literature review was conducted on offline and online platforms. Our survey revealed (a) continuation of a historical trend in classical biomanipulation practices (61.64%) and (b) an ascending drift in eco-bioengineering research (38.36%) in the last decade (2010-2021). At a global scale, recent biomanipulation research has a skewed distribution in Europe (41.10%), East Asia (32.88%), North America (10.96%), South Africa (4.11%), South America (2.74%), Middle East (1.37%), Oceania (1.37%), and non-specific regions (5.48%). Finally, this review analysis revealed the comprehensiveness of eco-bioengineering methods and their strong ecological resilience to recurrence of eutrophication and fluctuating environmental flows in the future. Therefore, our review reinforces the supremacy of eco-bioengineering methods as cost-effective green technologies providing sustainable solutions to restore the eutrophic waters at a global scale.

Aquaculture wastewater treatment through microalgal. Biomass potential applications on animal feed, agriculture, and energy

The use of microalgae to remediate raw effluent from brown crab aquaculture was evaluated by performing batch mode growth tests using separately the microalgae Chlorella vulgaris (Cv), Scenedesmus obliquus (Sc), Isochrysis galbana (Ig), Nannocloropsis salina (Ns), and Spirulina major (Sp). Removal efficiencies in batch growth were 100% for total nitrogen and total phosphorus for all microalgae. Chemical oxygen demand (COD) remediations were all above 72%. Biomass productivity varied from 20.9 mg L^-1 day^-1 (N. salina) to 146.4 mg L^-1 day^-1 (C. vulgaris). The two best performing algae were C. vulgaris and S. obliquus and they were tested in semi-continuous growth, reaching productivities of 879.8 mg L^-1 day^-1 and 811.7 mg L^-1 day^-1, respectively. The bioremediation of the effluent was tested with a transfer system consisting of three independent containers and compared with the use of a single container. The single container had the same capacity and received weekly the same volume of effluent as the three containers together. The remediation capacity of the 3 containers was much higher than the single one. The supplementation with NaNO₃ was tested to improve the nutrient removal microalgae' capacity, with positive results. The removal efficiencies were 100% for total nitrogen and total phosphorus and higher than 96% for COD. The obtained C. vulgaris and S. obliquus biomass were composed of 31 and 35% proteins, 6 and 8% lipids, 39 and 30% carbohydrates, respectively. The composition of these biomass suggest that it can be used as novel and sustainable ingredients in aquaculture feeds. The algal biomass of Cv and Sc were used as biostimulants in the germination of wheat and watercress, and very promising results were attained, with increases in the germination index for Cv and Sc of 175% and 48% in watercress and 84% and 98% in wheat, respectively. The biomasses of Cv and Sc were also subjected to a torrefaction process with 72.5 ± 1.7% char yields. The obtained biochars were tested as biostimulants for germination seeds (wheat and watercress) and as bio-adsorbent of dye solutions.