# Water and Wastewater Management in Agriculture
## 2 An Overview of Published Articles
(contribution 8) focuses on the utilisation of agricultural wastewater for the cultivation of microalgae for animal feed production and aims to influence the production costs of microalgae and the properties of the final product. In this study, the effectiveness of _Moringa oleifera_ seed powder (MP) as a biofoculant was compared with two chemical alternatives, aluminium sulphate (AS) and ferric chloride (IC), for the harvesting of a mixed microalgae culture (_Chlorella vulgaris_ and _Desmodesnus sp_.) grown on digestate. While MP showed the most consistent flocculation performance, it achieved a lower harvesting efficiency of 75% compared to 94% for AS and 100% for IC. Factors such as pH, mixing time, the grinding method for powder preparation, and granulometry showed no significant effect on the harvesting efficiency of MP, emphasising its robust nature as a flocculant. The introduction of a water extraction step increased the harvesting efficiency of MP to 91% but required a higher flocculant dosage. The microalgae harvested with MP met the maximum permitted levels for pigs, cattle, and poultry for most trace elements. However, all algae samples had elevated Fe and Al levels above the recommended levels, and this was likely due to the presence of metal-rich digestate particles. The research of [PERSON] et al. (contribution 9) focuses on the adsorption of phosphorus by lake bottom sediments, a crucial aspect in the management of eutrophication processes. In lake ecosystems, phosphorus is predominantly stored in the surface layers of bottom sediments, which account for over 90% of the element. Therefore, understanding the ability of the sediment to bind and release phosphorus is crucial for assessing the functioning of the lake ecosystem, especially for remediation measures. The study was conducted at Lake Kortowskie, which was renaturalised via hypolimnetic extraction in 1956. Sediment core samples were taken from two research stations: an experimental station with a maximum depth of 17.2 metres and a control station with a maximum depth of 15.7 metres. Laboratory experiments were carried out to analyse phosphorus adsorption. The results showed that phosphorus adsorption in the bottom sediments of Lake Kortowskie is complicated. The experimental data best fit the Freundlich, BET and Freundlich-Langmuir adsorption models. The adsorption isothermsshown concave curves, indicating a higher efficiency of phosphorus adsorption at higher phosphorus concentrations in the surrounding water. The research by [PERSON] et al. (contribution 10) focuses on the efforts to restore the heavily eutrophic Lajske Lake, which is located in the Masurian Lake District in Poland. This lake, which covers an area of 48 hectares and has a maximum depth of 7.4 metres, is contaminated by pollutants from its agricultural catchment area. Lake Lajske is a shallow reservoir with a wide depth zone that is completely deoxygenated in the summer. It plays an important natural and social role, which has led to remediation initiatives. Artificial oxygenation is an important method for improving water quality. In view of the unfavourable morphometric conditions, the introduction of multi-point aeration was deemed necessary. In 2019, a test facility with eight reactors was put into operation, which selectively enriches the water above the lake bed with oxygen. In 2021, spatial investigations were carried out to evaluate the effectiveness of aeration at 96 measuring points grouped in 12 test fields around each reactor. These tests were carried out three times during the summer season. The results showed a noticeable increase in oxygen concentration around all reactors, averaging 1-2 mg/L, especially in the deepest layers of the lake. The effectiveness of oxygenation varied and was related to the distance from the aerator and its position in relation to the direction of the outflow of oxygenated water. The research results confirm the feasibility of developing multipoint oxygenation systems to rehabilitate water bodies impacted by agricultural catchments.