Animal slurry contains plant nutrients that are essential for crop production. However, intensive livestock production may lead to a surplus of plant nutrients on farms and, as a consequence, discharge or emission to the environment. In order to ensure that the slurry applied to fields matches the nutrient requirements of the crops, techniques have been developed to reduce the nutrient content of slurry by means of separation. This review discusses the separation technologies used for animal slurry treatment and the physical and chemical processes involved in separation. These processes need to be understood before efficient, reliable and cheap separation technologies that take into account the actual properties of slurry and the likely end-use of the separation products can be developed. A simple separation efficiency expression can be used to assess the efficiency of slurry separation. It is indeed important to measure the amount and composition of the slurry before treatment, the dry-matter-rich fraction and the liquid fraction. The separation efficiency of mechanical separators for the removal of dry matter and phosphorus (P) is ranked as follows: centrifugation > sedimentation > non-pressurized filtration > pressurized filtration. In general, the separation of total N and NH ⁺₄ 4 follows the same pattern, but the separation efficiency is lower than for dry matter and P. Treatment with a flocculant before separation improves separation efficiency significantly. Of the polyacrylamide polymers tested, high-molecular-weight, linear cationic polymers with a medium charge density (20–40 mol%) were found to be the most efficient flocculants. The best mechanical separation techniques for flocculated slurry are screens or filter belts. The separation efficiency of polyacrylamide-treated slurry can be improved by adding a multivalent ion to coagulate particles and for precipitation of phosphorus. Aluminium sulfate (Al₂(SO₄)₃) or ferric chloride (FeCl₃) seem to be very efficient for improving the mechanical separators. Alternatively, the mineral struvite (MgNH₄PO₄) may be formed by changing the slurry characteristics, such as by the addition of magnesium (Mg) or by increasing the pH to 9. The struvite crystals are removed during solid-liquid separation. The products of the solid—liquid separation may be further treated by evaporation, membrane filtration or ammonia stripping in order to obtain the desired end-products; however, low-maintenance and/or cost-efficient operation of these post-treatments has not yet been demonstrated. The separation should be developed as a whole-system approach, paying attention to parameters such as the value of end-products, environmental consequences and economy.

中文翻译：

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理论和实践中对动物粪便进行固液分离。回顾

动物粪便含有植物营养，对作物生产至关重要。然而，集约化畜牧生产可能导致农场中植物营养素的过剩，并因此导致向环境的排放或排放。为了确保施用到田间的泥浆与农作物的营养需求相匹配，已开发出通过分离降低泥浆中营养成分的技术。这篇综述讨论了用于动物泥浆处理的分离技术以及分离所涉及的物理和化学过程。在开发有效，可靠和廉价的分离技术之前，需要先了解这些过程，这些技术要考虑浆液的实际特性以及分离产品可能的最终用途。一个简单的分离效率表达式可以用来评估浆液分离的效率。在处理之前，测量浆液的量和组成，富含干物质的馏分和液体馏分的确非常重要。机械分离器用于去除干物质和磷（P）的分离效率的等级如下：离心>沉淀>非加压过滤>加压过滤。通常，总氮和总氮的分离 非加压过滤>加压过滤。通常，总氮和总氮的分离 非加压过滤>加压过滤。通常，总氮和总氮的分离 ⁺ ₄ 4遵循相同的模式，但分离效率低于干物质和磷的分离效率。在分离之前用絮凝剂处理可显着提高分离效率。在测试的聚丙烯酰胺聚合物中，中等电荷密度（20–40 mol％）的高分子量线性阳离子聚合物被认为是最有效的絮凝剂。絮凝淤浆的最佳机械分离技术是筛网或滤带。聚丙烯酰胺处理的浆料的分离效率可以通过添加多价离子以使颗粒凝结并沉淀磷来提高。硫酸铝（Al ₂（SO ₄） ₃）或氯化铁（FeCl ₃）对于改进机械分离器似乎非常有效。可替代地，可以通过改变浆料特性，例如通过添加镁（Mg）或通过将pH提高到9来形成鸟粪石矿物（MgNH ₄ PO ₄）。在固液分离期间除去鸟粪石晶体。固液分离的产物可以通过蒸发，膜过滤或氨汽提进一步处理，以获得所需的最终产物。然而，这些后处理的维护成本低和/或具有成本效益的操作尚未得到证实。分离应作为一种全系统方法进行开发，并应注意最终产品的价值，环境后果和经济性等参数。