Safferman Steven I, Burks Bennette D, Parker Robert A
Department of Civil and Environmental Engineering, University of Dayton, OH 45239-0243, USA.
Water Environ Res. 2004 Sep-Oct;76(5):404-12. doi: 10.2175/106143004x151671.
The need to improve on-site wastewater treatment processes is being realized as populations move into more environmentally sensitive regions and regulators adopt the total maximum daily load approach to watershed management. Under many conditions, septic systems do not provide adequate treatment; therefore, advanced systems are required. These systems must remove significant amounts of biochemical oxygen demand (BOD) and suspended solids, and substantially nitrify, denitrify, and remove phosphorus. Many existing advanced on-site wastewater systems effectively remove BOD, suspended solids, and ammonia, but few substantially denitrify and uptake phosphorus. The purpose of this research was to design and test modifications to an existing on-site wastewater treatment system to improve denitrification and phosphorus removal. The Nayadic (Consolidated Treatment Systems, Inc., Franklin, Ohio), an established, commercially available, extended-aeration, activated sludge process, was used to represent a typical existing system. Several modifications were considered based on a literature review, and the option with the best potential was tested. To improve denitrification, a supplemental treatment tank was installed before the Nayadic and a combination flow splitter, sump, and pump box with a recirculation system was installed after it. A recirculation pump returned a high proportion of the system effluent back to the supplemental treatment tank. Two supplemental treatment tank sizes, three flowrates, and three recirculation rates were tested. Actual wastewater was dosed as brief slugs to the system in accordance with a set schedule. Several ion-exchange resins housed in a contact column were tested on the effluent for their potential to remove phosphorus. Low effluent levels of five-day biochemical oxygen demand, suspended solids, and total nitrogen were achieved and substantial phosphorous removal was also achieved using a 3780-L supplemental treatment tank, a recirculation ratio of 5:1, and a fine-grain activated aluminum-oxide-exchange media. Good results were also obtained with an 1890-L supplemental treatment tank and a recirculation ratio of 3:1. The most significant benefit of the supplemental treatment tank, in combination with the recirculation system, appears to be the low nitrogen concentration dosed to the Nayadic. By reducing the nitrogen concentration and spreading out its mass over time during no-flow periods, the Nayadic's inherent low-level denitrifying capacity was more closely matched and effective treatment was achieved.
随着人口向环境更为敏感的地区迁移，以及监管机构采用流域管理的每日最大总负荷方法，改进现场废水处理工艺的需求日益凸显。在许多情况下，化粪池系统无法提供充分的处理；因此，需要先进的系统。这些系统必须去除大量的生化需氧量（BOD）和悬浮固体，并进行充分的硝化、反硝化和除磷。许多现有的先进现场废水处理系统能有效去除BOD、悬浮固体和氨，但很少能进行充分的反硝化和吸收磷。本研究的目的是设计并测试对现有现场废水处理系统的改进措施，以提高反硝化和除磷能力。纳亚迪克系统（联合处理系统公司，俄亥俄州富兰克林）是一种成熟的、商业可用的延时曝气活性污泥工艺，被用作典型的现有系统。基于文献综述考虑了几种改进措施，并对最具潜力的方案进行了测试。为提高反硝化能力，在纳亚迪克系统之前安装了一个补充处理池，并在其后安装了一个组合式分流器、集水坑和带有再循环系统的泵箱。一台再循环泵将系统流出物的很大一部分回流到补充处理池。测试了两种补充处理池尺寸、三种流量和三种再循环率。按照设定的时间表，将实际废水以短脉冲形式注入系统。在接触柱中放置了几种离子交换树脂，测试其对流出物中磷的去除潜力。使用一个3780升的补充处理池、5:1的再循环率和细颗粒活性氧化铝交换介质，实现了五日生化需氧量、悬浮固体和总氮的低流出水平，同时也实现了大量的磷去除。使用一个1890升的补充处理池和3:1的再循环率也取得了良好的效果。补充处理池与再循环系统相结合的最显著好处似乎是进入纳亚迪克系统的氮浓度较低。通过降低氮浓度并在无流量期间将其质量分散开来，纳亚迪克系统固有的低水平反硝化能力得到了更有效的匹配，从而实现了有效的处理。
