Suchergebnisse

AbstractTraditionally, the design of settlement tanks has been based on practical experience linked to key criteria, which have evolved from many sources. In this paper, the design criteria which affect the performance of both primary and secondary tanks are examined and a procedure, linked to critical velocities and loading rates, is put forward to enable the design requirements to be rationalized.Based on the authors' considerable practical experience, the proposed procedure can be used with confidence to design tanks which will achieve required performance, particularly in the case of secondary tanks (for separation of both activated and humus sludges). In particular, the importance of a correctly sized inlet stilling chamber, to reduce the feed velocity to around 0.003–0.005 m/s is explained.The use of chemicals to aid removal of suspended solids (and hence BOD) has been practised for many years. Today, there is renewed interest, particularly for phosphate removal and for the treatment of some industrial wastewaters. The composition and nature of sewage affects the potential benefits of coagulant chemicals when added at the treatment works' inlet. The introduction of organic polymers has significantly improved performance and reduced costs. The major disadvantage of using chemicals relates to the significant increase in quantity of sludge that is produced, which will require both treatment and disposal, increasing operational costs.

ABSTRACTDavyhulme sewage‐treatment works, which serves the Manchester drainage area, is one of the lagest in the UK. The dry‐weather flow is 300 000 m3/d, and the plant receives a wide range of industrial effluents. The works has been identified as a major source of pollution in the Mersey estuary, with an average discharge of 6500 kg ammonia/day. As part of its initiative to improve the Mersey estuary, North West Water intends to reduce the daily ammonia load from Davyhulme to about 1000 kg/d by 1995. In order to assess the capabilities of both conventional and novel processes to achieve this degree of ammonia removal, a number of on‐site pilot plants were established. This paper reports on the pilot‐plant studies and the selection of process options. Recommendations with regard to design parameters and final process selection are given.

The Mw 6.4 and Mw 7.1 Ridgecrest earthquake sequence occurred on 4 and 5 July 2019 within the eastern California shear zone of southern California. Both events produced extensive surface faulting and ground deformation within Indian Wells Valley and Searles Valley. In the weeks following the earthquakes, more than six dozen scientists from government, academia, and the private sector carefully documented the surface faulting and ground-deformation features. As of December 2019, we have compiled a total of more than 6000 ground observations; approximately 1500 of these simply note the presence or absence of fault rupture or ground failure, but the remainder include detailed descriptions and other documentation, including tens of thousands of photographs. More than 1100 of these observations also include quantitative field measurements of displacement sense and magnitude. These field observations were supplemented bymapping of fault rupture and ground-deformation features directly in the field as well as by interpreting the location and extent of surface faulting and ground deformation from optical imagery and geodetic image products. We identified greater than 68 km of fault rupture produced by both earthquakes aswell as numerous sites of ground deformation resulting from liquefaction or slope failure. These observations comprise a dataset that is fundamental to understanding the processes that controlled this earthquake sequence and for improving earthquake hazard estimates in the region. This article documents the types of data collected during postearthquake field investigations, the compilation effort, and the digital data products resulting from these efforts.