Aspects of wastewater characterization, in particular settling velocity distributions, and its relevance on the performance of physical unit processes such as sedimentation and filtration are described and used to explain why satellite treatment makes sense. The satellite CSO treatment facilities at Columbus, Georgia which have undergone more than 5 years of peer reviewed intensive monitoring are described and used as a case example to highlight the benefits and significant cost savings that accrue from implementing satellite treatment systems within collection systems.

To alleviate the problem the Environment Agency and Halcrow Group developed an upstream on-line storage reservoir scheme. The project includes a 450m long, 6.8m high clay embankment across the valley, with a culvert on the line of the original river channel to carry the controlled outflow. A 150m long concrete-block spillway carries excess flood flows over the embankment. The embankment site has been landscaped to minimise visual impacts and the borrow area has been developed into a large wetland area as a habitat for aquatic flora and fauna.

The key component of the flow control system is a 6.5 tonne, stainless steel Hydro-Brake® Flow Control device located in the dam inlet structure. The Hydro-Brake® was designed by Hydro International to control the maximum outflow rate despite fluctuating head, and incorporates the facility to adjust the controlled outflow between 8 and 12m3/s. The use of the Hydro-Brake® helped reduce the upstream storage requirement and hence the land take and frequency of flooding involved. This paper provides a description of the options considered during the design stage of the flood defence scheme, details of the actual design and construction of the dam, an explanation of how the Hydro-Brake® operates and the benefits it provides over other forms of flow control.

Authors

Barter, P. and Smith, J.

Abstract

With the challenge of meeting new tighter ammonia consents in municipal wastewater treatment, tertiary aerated sand filters, combining the solids removal aspects and selfcleaning properties of continuously backwashed up-flow filters (CoUF’s) with the ammonia conversion capabilities of an attached growth filter are becoming increasingly popular. With specific reference to the DynaSand / DynaOxy system, this paper examines how the filters work, covering their form and operation and what mechanisms are used in their control. The optimisation of process air requirements to maximise the ammonia conversion effectiveness of biomass is considered, along with energy consumption issues and operational practices required to ensure efficient operation in the longer term. The results of a monitoring study of a full-scale installation treating a dry weather flow of over 2000 m3/day are presented.