Water Environment

This manuscript describes the application of a genetic algorithm model for the optimal design of regional wastewater systems comprised of transmission gravitational and pumping sewer pipelines, decentralized treatment plants, and end users of reclaimed wastewater. The algorithm seeks the diameter size of the designed pipelines and their flow distribution simultaneously, the number of treatment plants and their size and location, the pump power, and the required excavation work. The model capabilities are demonstrated through a simplified example application using base runs and sensitivity analyses. Scaling of the proposed methodology to real life wastewater collection and treatment plants design problems needs further testing and developments. The model is coded in MATLAB using the GATOOL toolbox and is available from the authors.

Anaerobic digestion is an appropriate technique for the treatment of sludge before final disposal and it is employed worldwide as the oldest and most important process for sludge stabilization. In general, mesophilic anaerobic digestion of sewage sludge is more widely used compared to thermophilic digestion. Furthermore, thermal pre-treatment is suitable for the improvement of stabilization, enhancement of dewatering of the

Floating mats are locally known as phumdis. They are a heterogeneous mass of soil, vegetation and organic matter at various stages of decomposition. Phumdis play an important role in the ecological processes and functions of the lake ecosystem. The presence of phumdis is the characteristic feature of the Loktak lake, the largest freshwater wetland located in the north-eastern part of India about 38 km from Imphal city of Manipur. Phumdis cover nearly 50% of the lake. In this paper, an attempt has been made to examine the changes in phumdi area, analyse the factors causing its proliferation and the resultant impacts on the environment. The study is based on remotely sensed data of 1989 and 2002. To examine the factors causing its proliferation, field surveys were conducted and data covered eight villages and 377 households. The results showed that the phumdi area has increased from 1989 to 2002. The main causes for phumdi proliferation were the construction of the Ithai Barrage Dam, increase in athaphum fishing, pollution, growth of settlements on phumdis, etc. It was the human pressure that has aided in the growth of phumdis.

An artificial neural network (ANN) model was developed to predict boundary shear force distributions in smooth rectangular channels and ducts. Currently the designers often obtain these values with the help of semi-empirical methods. In this paper, as an alternative to these methods, a neural network model is presented. The model was trained and tested using 94 experimental data obtained from the works of best known researchers in this field. The proposed ANN model was found to be superior to existing methods for most of the data sets studied.

The measurement of flows and recording of storm events at combined sewer overflows are a key requirement in effective urban pollution management. Staff of Thames Water Utilities have developed a low-cost system based on monitoring the behaviour of flap valves on numerous major river outfalls. The paper presents the development of a modelling approach based on the principle of conservation of angular momentum and its application to experimental data for circular gates. Flow-prediction accuracies, based on the measurement of gate inclination and water depths, in the range ± 20–30%, are found to be achievable for wider gate openings (<20°) – the recommended calibration offering conservative flow predictions at lower angles.

Abstract The Water Framework Directive (WFD) provides a coherent structure within which the problems of diffuse urban pollution can be effectively tackled and managed. The context of impermeable surface water quality within the terms of the Directive are outlined, and the pollutant sources and loadings associated with various urban land uses are identified. Stormwater flows and quality are sufficient to prejudice any &amp;amp;amp;#x27;good&amp;amp;amp;#x27;ecological potential, particularly in terms of chronic receiving water sediment toxicity. A simple volume– ...

The Deepor Beel is a natural, freshwater wetland in the south-west corner of Guwahati, India. The Beel harbours a large number of migratory aquatic birds, especially in winter, and is a Ramsar site since 2002. The wetland provides livelihood to the people of the surrounding villages through collection and sale of fish, nymphaea nuts and flower, ornamental fish, orchids, medicinal plants, etc. The water quality of the Beel is threatened by excessive fishing, hunting of water birds, pollution from pesticides and fertilizers and infestation by water hyacinth. The present work reports on the water quality of the wetland by continuous monitoring from February to July, covering the dry, temperate period and the wet, hot and humid period. Sampling was carried out at 10 sites for physical and aggregate properties, metallic and nonmetallic constituents, organic contaminants and microbiological parameters.

In the past, river engineering works have often caused channel instability and adversely affected the river's conservation and amenity value. Recent guidelines have advocated a more natural approach to river engineering practice which retains habitat diversity within the river system. While a more natural approach is desirable, geomorphological guidance is required to ensure that the advocated changes are feasible and sustainable, both in the long and short term. The key requirement for sound environmental river engineering is a basic understanding of the natural processes controlling channel shape and dimensions. Examples are given in the paper to illustrate how such knowledge can be used to (a) stabilize rivers, (b) design environmentally-acceptable and stable flood-alleviation schemes, and (c) restore previously canalized rivers. The basis of the geomorphological input in the assessment and design process is a river survey which determines the factors controlling channel characteristics and how it will respond to planned changes.

This paper provides a review of the treatment technologies, which utilize natural processes or passive components in wastewater treatment. In particular, this paper primarily focuses on wetland systems and their applications in wastewater treatment (as an advanced treatment unit or decentralized system), nutrient and pollutant removal (single and multiple pollutants, and metals), and emerging pollutant removal (pharmaceuticals). A summary of studies involving the plant (vegetation) effects, wetland design and modeling, hybrid and innovative systems, storm water treatment and pathogen removal is also included.