Primary wastewater treatment

The capital cost of most aqueous waste treatment operations is proportional to the total flow of wastewater, and the operating cost increases with decreasing concentration for a given mass of contaminant to be removed. Thus, if two streams require different treatment operations, it makes no sense to mix them and treat both streams in both treatment operations. This will increase both capital and operating costs. Rather, the streams should be segregated and treated separately in a distributed effluent treatment system. Indeed, effective primary treatment might mean that some streams do not need biological treatment at all. 

Wet Air Oxidation. With wet air oxidation, increased temperature and pressure are used to oxidize dilute concentrations of organics and some inorganics, such as cyanide, in aqueous wastes that contain too much water to be incinerated, but are too toxic to be treated biologically. In general, wet air oxidation provides primary treatment for wastewaters that are subsequendy treated by conventional methods. This technology can be used with wastes that are pumpable (slurries andUquids). 

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. 

WWTP Population equivalent Flow (m" h- ) Receiving river water Type of wastewater treated Hydraulic retention time Primary treatment Secondary treatment... 

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. 

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... 

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... 

The fate of surfactants (Fig. 1.17) in wastewater treatment plants (WWTP) is determined by, among other factors, the composition of the wastewater, the operational type of the WWTP and the physicochemical properties of the surfactant molecule itself. In general, WWTPs provide a primary treatment, which is simply the removal of solid materials by mechanical means. 

In the Strait of Georgia, Canada, a study was performed on the fate of AgPEO in marine sediments [28]. Box core sediment samples were taken in a region heavily impacted by two municipal wastewater effluents. The sewage only receives primary treatment, which is clearly reflected in the results of this study. 

In addition, oily sludge from a wastewater treatment facility that results from treating sour wastewaters may be a hazardous waste (unless recycled in the refining process). These include API separator sludge, primary treatment sludge, sludge from various gravitational separation units, and float from dissolved air flotation units. 

Some fixed filtration systems are relatively inexpensive. For example, constructed wetlands and sand filters are generally the most successful methods of polishing the treated wastewater effluent from lagoons. These systems have also been used with more traditional, engineered primary treatment technologies such as septic tanks and primary clarifiers. In such constructed wetlands, the system utilizes the roots of plants to provide substrate for the growth of attached bacteria, which utilize the nutrients present in the effluents and for the transfer of oxygen. 

The vendor claims that Ensol is applicable for the treatment of wastewaters including sewage after primary treatment, metal plating and finishing waters, and paper mill white water. The claim also extends to the treatment of solid wastes and soils, provided that they contain sufficient free water. 

The vendor states that MRRP may not be cost effective for contaminated water or wastewater as a primary treatment system but could recover mercury from carbon systems used to treat these waste streams. According to the Gas Technology Institute, the mobilization and demobilization of mobile thermal treatment systems can be costly and time consuming. These technologies are often energy intensive. 

In the next step, called primary treatment, the screened wastewater enters a large settling basin where solid particles too fine to have been caught by the screen settle out as sludge. After a period of time, the sludge is removed from the... 

---