Objectives of Wastewater Treatment:
To kill the pathogens
To improve the quality of wastewater
To avoid unhygienic conditions
To protect the aquatic life from the toxicity wastes
To make the wastewater usable for agricultural, aquaculture etc.
There are three constituents and interrelated aspects of waste water management.
Collection of wastewater
Collection of domestic wastewater is best achieved by a full sewerage water drain age system. Unfortunately this method is most expensive and there is relatively few communities in hot climate which afford it. A modern hygienic method of night soil collection is the only realistic alternative.
Treatment of wastewater
Treatment is required principally to destroy pathogenic agents in sewage or night soil and to encore that it is suitable for whatever re-use process is secreted for it.
Re-use of wastewater (Recycling of wastewater)
The responsible re-use of night soil and sewage effluent is aqua culture and crop irrigation can make a significant contribution to a community food supply and hence it’s general social development. The best example is china where over 90% of waste after treatment is applied to land.
Performance criteria for Wastewater Treatment Management System:
The ideal system would satisfy all of the following criteria.
Pathogenic organisms should not be spread either by direct contact with right soil or sewage or indirectly via soil, water or food. The treatment chosen should achieve a high degree of pathogen destruction.
The treatment process should yield a safe product for re-use, preferably in aquaculture and agriculture.
In those cases land the should be considered exception when the waste cannot be re-use, the discharge of effluent into a surface water should not exceed the self-purification capacity of the recipient water.
The degree of odor release must be below the nuisance threshold. No part of the system should become aesthetically offensive.
The methods chosen for waste collection, treatment and re-use should be compatible with local habits and social (religious) practice.
The skills required for the routine operation and maintenance of the system components must be available locally or are such that they can be acquired with only minimum training.
Capital and running costs must not exceed the community’s ability to pay. The financial return from re-use schemes is an important factor is an important factor in this regard.
However, no one system completely satisfies all these demands. The problem becomes one of minimizing disadvantages.
Waste Water treatment Processes:
Municipal wastewater is primarily organic in content and a significant number of industries including chemical pharmaceutical and food have high organic waste load. This means that the main treatment processes are geared towards organic removal. In a typical treatment plant, the wastewater is directed through a series of physical, chemical and biological processes each with specific waste load reduction task. The tasks are typically.
Pre-treatment ==> Physical and / or chemical
Primary treatment ==> Physical
Secondary treatment ==> Biological
Advanced treatment ==> Physical and / or chemical and / or biological.
Conventional Wastewater Treatment Plant Processes:
Conventional treatment or conventional mechanical wastewater treatment is the term used to describe the standard method of treatment designed to remove organic matter and solid from solution. It comprises four stages of treatment.
Preliminary treatment ( influent flow measurement, screening (Bar racks), Shredders, comminutors (maceratours), pumping, grit removal)
Primary treatment (sedimentation)
Secondary treatment (biofitration or activated sludge)
Sludge treatment (anaerobic digestion of the sludge produced in primary and biological treatment)
Originally posted on SANDRP:
Rivers are again in the news, though so far only for symptomatic reasons. The new government at the centre has renamed the charge of water resources minister to Minister of Water Resources, River Development and Ganga Rejuvenation. There is fundamental contradiction within this name plate and we have in fact yet to see this nameplate.
There is also a lot of discussion about rejuvenation of Ganga, with the Prime Minister promising the people of Varanasi Parliamentary constituency that he will rejuvenate Ganga. There is no clarity about how he plans to go about in achieving that. His claim during elections that Gujarat Government’s Sabarmati Riverfront Development provides a model for this is clearly a non-starter. Sabarmati has water only in 10.4 km of the river stretch that flows through Ahmedabad. If you go upstream of this stretch, you will find a dry river in most non-monsoon months and if you go downstream, you will…
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When the soil beneath the level at which a footing or raft would normally be established is too weak or too compressible to provide adequate support, the loads are transferred to more suitable material at a greater depth by means of piles or piers. The distinction between the two is somewhat arbitrary.
Piles are the structural members of small cross-sectional area compared to their length, and are usually instated by a driver consisting of a hammer or a vibrator. They are often grouped into clusters or rows, each containing enough piles to support the load delivered by a single column or wall.
Important Factors To Consider During Pile Design
A lightly loaded column may, in some instances, require only a single pile. However, since under field conditions the actual position of a pile may be as much as several inches from its planned location, an eccentric loading can hardly be avoided. Consequently, the heads of single piles are usually braced in two directions by grade beams. If only two piles are needed, their heads may be connected by a concrete cap braced by grade means in only one direction, perpendicular to the line joining the two piles Fig.1(b). Clusters containing three or more piles are provided with reinforced concrete caps, as shown in Fig.1(c), and are considered stable without support by grade beams.
Vertical piles may also be used to resist lateral loads as for example, beneath a tall chimney subject to wind. Compared to their axial capacity, the lateral capacity is usually small. Where large lateral loads are to be used (Fig.1d.) Batters of 4 horizontal : 12 vertical represent about the greatest inclination that can be achieved with ordinary driving equipment. Economy usually favors smaller inclinations even if more piles have to be battered.
Functions of Pile Foundation
Piles are used if the bearing capacity of soil at shallow depth is not enough to withstand the structural load. So the piles are driven to transfer the loads from the structure to the high bearing capacity soil/rock stratum. The main functions of using pile foundations are listed below in short.
- To transfer the load from the structure to the foundation at a greater depth where the \bearing capacity of soil is efficient to withhold the structure loads.
- Pile controls the soil settlement which can be accompanied by surface foundations.
- Piles are used to increase the safety factor for high loaded structures.
- Piles enable the scope of construction in very low bearing capacity soils
Note : Article Courtesy : http://civilengineersforum.com/function-of-pile-foundation/