Burnley Sewage-Treatment Works: Design and Operation of a High-Rate Nitrifying Filter

The paper deals with the planning, construction, operation and performance of the purpose-built nitrifying filter from its commissioning in August 1986 to the present day. Burnley sewage-treatment works consists of inlet screens, Dorr detritors, primary sedimentation tanks, surface-aeration activated sludge units, and final settlement; sludge is digested and tankered to farmland.
The filter was designed and built following the closure of several local works and subsequent diversion of flows to Burnley. It was realized that the increased volume from the extended Burnley works would reduce the dilution of the effluent by the River Calder. This would result in a deterioration in the quality of the river. As a consequence an ammonia standard of 14 mg/l was imposed on the works following the completion of the nitrifying filter.     

The Use of Different Conveyance Calculations for Modelling Flows in a Compact Compound Channel

Flow measurements have been taken for steady and unsteady flows on a reach of a river having a compact compound channel. The 'single channel', 'divided channel' and 'lateral' distribution methods have been used to calculate conveyances for use in a one-dimensional unsteady flow model of the reach. Comparisons with measured flows show that the divided channel method and the lateral distribution method both underestimate floodplain flow depths. The lateral distribution method gives the closest accuracy in the relative depth range 0.15 ≤ Yr < 0.40. For large flow depths the single channel method becomes more accurate and slightly over-estimates flow depths.
The accuracy of unit width discharge distributions, calculated from the lateral distribution method are assessed by comparison with observed distributions for overbank flows.     

Groundwater Model of Conditions in Liverpool Sandstone Aquifer

T his study considers the groundwater conditions for the period 1948–82 in the Permo-Triassic Sandstone aquifer of the Liverpool area. During this period, significant changes have occurred in the abstraction patterns and a new railway tunnel has been constructed below sea level in Central Liverpool. To understand the flow conditions within the aquifer, detailed studies have been carried out into the aquifer properties, the influence of rivers and tunnels, and the estimation of recharge. It is found that conventional rainfall recharge accounts for only one-third of the total recharge.
Numerical model solutions were used to check the adequacy of the understanding of the flow processes and the solutions have confirmed that the rising water levels in Central Liverpool result from high recharge and a reduction in abstraction. Having validated the model by comparisons with field data, the model was then used to predict the probable future water level changes.     

Economic Optimization of Distribution Leakage Control

E vry WATER DISTRIBUTION system has an economic optimum level of leakage. To maintain that optimum level of leakage there is a corresponding optimum level of leakage control activity.
Despite much work on this subject, particularly in recent years with publication of DoE Report No. 26¹, many undertakers remain unclear about their economic optimum leakage level and how much effort is required to maintain that level.
This paper describes development of an economic model which attempts to quantify optimum leakage through measurement of parameters which should be readily available or obtainable.
The model was originally developed specifically for routine sounding. However, extension of the basic principles allows development of a general optimization theory. The paper then shows how the theory can be applied to optimization of district metering     

Post-Implementation Appraisal of a Two-Stage Channel in the River Roding, Essex

T he performance of a two-stage river channel is examined from a combination of collected field data on the River Roding and a hydraulic model study. Particular attention is paid to the vegetation on the upper channel berm, including its seasonal effect on hydraulic resistance and the problem of channel maintenance. Recommendations are made with respect to (a) increasing the present capacity of the River Roding, and (b) the future design of two-stage flood channels intended to meet stringent environmental standards.     

The Reliability of Groundwater Sources to Meet Increasing Demands

The groundwater resources of the Lee Valley Water Company have been examined in a joint study with the University of Birmingham. The Company is modifying its operating policy to make maximum use of the groundwater resources, which has involved the development of new methods of estimating the reliable output of the groundwater sources under differing conditions. The technology transfer involved in the project has enabled the Company to gain a greater understanding of the operation of its sources, and the University has modified existing techniques so that they are of greater practical use.     

Excluding Groundwater Infiltration into New Sewers

Much attention has been focused on the need for sewer renovation and rehabilitation of old sewerage systems, but age is not always the reason for sewer failure. Serious problems of performance have also been encountered on sewerage schemes less than 10 years old. This paper considers the problems of groundwater infiltration into new foul sewers, and suggests that deficiencies might exist in some aspects of modern sewer design and construction.
Infiltration is most frequently observed at sewer joints. Results are presented of laboratory tests which show the ability of flexible fixed-ring joints on clay sewers to withstand both internal and external pressures. Damaged polyester fairings on the spigots of these pipes can act as one-way valves, and massive infiltration may result. The standard site water test is shown to be inadequate in detecting some of these types of defect which may result from damaged pipes or poor workmanship.     

Precast Concrete Blocks for High-Velocity Flow Applications

Precast concrete blocks can be used as erosion protection to a surface subjected to high-velocity water, for example a dam spillway.
The paper describes model testing carried out on flat and wedge-shaped blocks in a purpose-designed facility at the University of Salford, where an open channel discharge intensity of 0.5 m²/s can be accelerated to a velocity of 7.5 m/s.
The failure modes of tied and untied flat concrete blocks have been investigated under different laying and bedding conditions. The model results are compared to the findings from prototype studies. Results from experiments on wedge-shaped blocks of a Soviet design are also presented and confirm the Russian experience that the wedge shape is inherently stable at large discharges, a block of 100-m thickness being stable under a discharge intensity of 20 m²/s.