Primary Treatment Processes

Primary or pretreatment of wastewater can involve either physical or chemical treatment, depending on the nature of the contamination, and serves three purposes  

The pretreatment processes may be most effective when applied to individual waste streams from particular processes or process steps before effluent streams are combined for biological treatment. 

A brief review of the primary treatment methods will now be given1 3. Pretreatment usually starts with phase separation if the effluent is a heterogeneous mixture. 

Solids separation. Methods used for solids separation include most of the commonly used techniques  

Settling to remove solids from aqueous effluent can be enhanced by the use of centrifugal forces in hydrocyclones. Their design was discussed in Chapter 8. For solids removal, the solids are driven toward the wall of the hydrocyclone and removed from the base. Centrifugation can also be used for solids removal, but restricted to smaller volumes. Solids removal by centrifugation can typically be in the range 50 to 80%, increasing to typically 80 to 95% with chemical addition. 

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Figure 21.8 shows a typical sequence of the major equipment systems in a wastewater treatment plant.36 The function of primary treatment is to remove suspended solids from the wastewater, and then to remove organic materials by biological secondary treatment. Primary treatment processes used by kraft mills typically involve screening followed by either sedimentation or flotation.40... 

Finding (Blue Grass) AEA-3. Long-term operation of the SILVER II cell membrane on all the required feed streams has not been demonstrated. Because the SILVER II process is the primary treatment process for agent and energetics, the committee is particularly concerned that the life of the cell membranes, on which the efficacy of the SILVER II process depends, has not been demonstrated. 

Primary treatment processes, such as clarification, lime-soda softening, ion-exchange, and RO... 

The numbered subsections that follow consider impurities not amenable to satisfactory control by the standard primary treatment process. We divide the impurities dealt with here into three groups ... 

The initial sample is called the primary, or gross sample and may be a single increment drawn from the target population, or a composite of several increments. In many cases the gross sample cannot be analyzed without further treatment. Processing the gross sample may be used to reduce the sample s particle size, to transfer the sample into a more readily analyzable form, or to improve its homogeneity. 

There are four stages preliminary, primary, secondary, and tertiary treatment processes, which differ mainly by the number of operations performed on the waste steams (2,3). 

Implementation of cleaner production processes and pollution prevention measures can yield both economic and environmental benefits. The primary treatment technologies afforded to this manufacturing include the following ... 

We will address some of these issues later on in this chapter. But for now, simply recognize the fact that the most basic part of waste water treatment is solids removal. Solids are removed in primary and secondary treatment tanks, but without such effective removal there is no treatment process efficiency. 

In a typical plant operation the pollutants dissolved in the wastewater or that would not settle in the primary clarifiers flow on in the wastewater to the Secondary treatment process. Secondary treatment further reduces organic matter (BOD,) through the addition of oxygen to the wastewater which provides an aerobic environment for microorganisms to biologically break down this remaining organic matter. 

Comminution Shredding. A mechanical treatment process which cuts large pieces of waste into smaller pieces so that they won t plug pipes or damage equipment. Contact stabilization Contact stabilization is a modification of the conventional activated sludge process. In contact stabilization, two aeration tanks are used. One tank is for separate reaeration of the return sludge for at least four hours before it is permitted to flow into the other aeration tank to be mixed with the primary effluent requiring treatment. 

Primary treatment A wastewater treatment process that takes place in a rectangular or circular tank and allows those substances in wastewater that readily settle or float to be separated from the water being treated. 

Secondary Treatment A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. Usually the process follows primary treatment by sedimentation. The process commonly is a type of biological treatment process followed by secondary clarifiers that allow the solids to settle out from the water being treated. Sedimentation The process of subsidence and deposition of suspended matter from a wastewater by gravity. 

Primary Raw Materials for Petrochemicals 3 NATURAL GAS TREATMENT PROCESSES... 

Where effluents require primary, secondary and possibly additional tertiary treatment, attention should be paid to the various treatment processes with regard to personnel safety and public sensitivity to on-site treatment. 

To limit the potential for waterside problems throughout the steam-water system cycle a balance of water treatment processes is required with external items of capital equipment providing primary duty for FW pretreatment and internal specialty chemicals providing a supporting, polishing function. 

The term external treatment is used to describe all of the different types of essential nonchemical processes employed to condition or remove some or all impurities in water before it reaches the FW pumps. There is often considerable overlap in the scope of common water treatment process technologies, and each of the primary processes can be divided into several subsets, giving rise to a wide range of impurity removal efficiencies for each process. 

Leaving aside FW deaeration (which is usually provided as the final type of external treatment in the pre-boiler section), the primary forms of treatment processes commonly employed can be conveniently categorized into three areas ... 

Water available on site not subjected to any in-house treatment process. City water, despite being treated at a primary city facility is described as raw water when being considered for suitability in industrial processes. 

This plant produces 130 m2/h of enameled steel and operates 3500 h/yr. It uses 0.0036 m3 water/m2 of product to coat the steel. Average process water flow is 0.144 m3/h for coating operations and 0.734 m3/h for metal preparation. The primary treatment in-place for process wastewater is clarification and settling. Other water treatment practices employed are pH adjustment with lime or acid, sludge applied to landfill, polyelectrolyte coagulation, and inorganic coagulation. 

In addition to process-integrated measures, consider primary treatment and biological treatment as BAT for kraft pulp mills... 

This treatment process employs the use of physical operations such as screening and sedimentation to partially remove suspended solids and organic matter from the wastewater. This process provides the secondary treatment with wastewater that is partially free of solids, in order to facilitate further treatment. The effluent from the primary treatment contains primarily organic matter and is characterized by a relatively high biochemical oxygen demand (BOD).2... 

The secondary treatment is linked to the primary treatment in a typical wastewater treatment plant. It is designed to remove soluble and colloidal organics as well as suspended solids that are not trapped in the primary treatment. The treatment processes employed in this section of the wastewater... 

To meet the specified standard,4 wastewaters are often subjected to a series of treatment processes before they are discharged into the environment, particularly, water bodies. The treatment processes include physical, chemical, and biological processes that may be applied singly or collectively. The collective application of the processes can be employed in a variety of systems classified as primary, secondary, and tertiary wastewater treatment, to achieve different levels of contaminants removal.2... 

Thermal treatment—Processes in which vapor-phase contaminants are destroyed via high-temperature oxidation the primary categories of thermal treatment used to treat MTBE and other oxygenates include thermal oxidation, which employs a flame to generate the high temperatures needed to oxidize contaminants, and catalytic oxidation, which employs lower temperatures in the presence of a catalyst (typically platinum, palladium, or other metal oxides) to destroy contaminants. 

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