Secondary treatment normally utilizes biological treatment processes activated sludge. Cotreatment of faecal sludge in municipal wastewater. This is rooted in the fact that in contrast to wastewater, which continuously passes. Secondary treatment the secondary stage of treatment removes about 85 percent of the organic matter in sewage by making use of the bacteria in it. The activated sludge process is the most commonly applied biological wastewater treatment technology. The sludge resulting from this process represents the next challenge for the water treatment industry, in particular the minimizing of its volume. Municipal wastewater and sludge treatment 47 oxygen demand or bod a measure of the amount of biodegradable organic material remaining in the treated wastewater and 30 mgliter of suspended solids particles removable by filtration. Preliminary and primary wastewater treatment processes a. Sludge produced during the wastewater treatment is estimated as 80 percent of biochemical oxygen demand bod load howard humphreys 1995. Evaluation of the sludge drying beds at sanaa wastewater treatment plant fadhl ali alnozaily1, taha mohammed taher2, mohammed howaidi m. Sludge is the unwanted byproduct of the wastewater treatment process. Many activated sludge configurations have evolved over the years, and, depending on the design, an activated sludge wwtp can. The relationship of municipal wastewater and sludge treatment to crop production is shown schematically in figure 3.
Technology and innovative options related to sludge management. Sewage sludge is the solid, semisolid, or slurry residual material that is produced as a byproduct of wastewater treatment processes. Rebecca stott, in handbook of water and wastewater microbiology, 2003. The development of new sludge processing technologies that reduce the volume of the final product whilst enhancing the quality for disposal as well as producing renewable energy are changing the shape of the industry. This sludge dewatering handbook will present the key parameters to take into account in order to. Wastewater treatment sludge treatment and disposal britannica. Digested sewage sludge is usually dewatered before disposal. Activated sludge is a biological process that utilizes microorganisms to convert organic and certain inorganic matter from wastewater into cell mass. Activated sludge is added to wastewater, and the mixture is aerated and agitated. Activated sludge process a biological wastewater treatment process which speeds up waste decomposition. Wastewater treatment plants are designed to process the raw sewage prior to its discharge to reduce its organic content, oxygen demand, and pathogenic content. In this process, a bacterial biomass suspension the activated sludge is responsible for the removal of pollutants.
As illustrated, reuse of wastewater for food crop production or in other reuse applications, such as ground water recharge or urban landscape irrigation, typically occurs after secondary wastewater treatment and may necessitate. The activated sludge process is very widely used for biological wastewater treatment. Emerging technologies for wastewater treatment and in. Physical, chemical and biological characteristics of wastewater 2. There are currently over 50,000 wastewater treatment works wwtps operating in the european union yielding a total of about 7. Notes on activated sludge process control page ii total solids are defined as all the matter that remains as residue upon evaporation at 103 to 105 oc.
In the activated sludge treatment process, the removal of suspended solids from wastewater is usually through gravity separation in a clarifier. Sewage sludge, at the outlet after mechanical drying, is made of approximately 80%. In the case of mechanical treatment, the sludge is produced on daily basis and treated by. The figure below shows a general flow diagram with the typical components present in an activated sludge wastewater treatment plant. One definition of a wastewater treatment plant operator is a bug farmer, one who controls the aeration basin environment to favor good microbiology. Lecture notes water and wastewater treatment engineering. With few exceptions, the cwa requires that municipal wastewater treatment plant discharges meet a minimum of secondary treatment. Today, the treatment of water is a wellknown process and is executed by state of the art techniques. Sludge is the semisolid slurry from a wastewater treatment plant. Wastewater treatment sludge treatment and disposal. For most treatment plants, this will be a portion of the return activated sludge ras flow stream.
The calculations refer to 100 cubic meters of wastewater entering the municipal treatment plant. This plant receives wastewater from both urban and industrial activities, and consists of a conventional activated sludge process with a primary treatment and two parallel activated sludge bioreactors, serving about 210,000 equivalent inhabitants 35,000 m3d. Activated sludge treatment process concept and system design. This is accomplished by utilizing treatment processes that remove. Activated sludge treatment process concept and system. Sludge may also be pumped offsite for long distances for treatment. Wastewater treatment wastewater treatment sludge treatment and disposal. Field trip to deer island wastewater treatment plant. Introduction to sludge handling, treatment and disposal. Wastewater collection systems are designed to convey raw sewage to a central location for treatment. The amount of sludge will continue to increase as the urban waste water treatment directive continues to be implemented cec, 1991, reaching at least 8. Total solids can be classified as either suspended solids or filterable solids by passing a known volume of liquid through a filter. Activated sludge is commonly used as a wastewater treatment. Because cells need oxygen for their metabolism, air is injected from the bottom of the aerator.
Wastewater and sludge treatment seepex pumps are widely used in industrial and municipal wastewater and sludge treatment. The settled sludge is either returned ras or wasted was. Wastewater treatment wastewater treatment dewatering. Dewatered sludge still contains a significant amount of wateroften as much as 70 percentbut, even with that moisture content, sludge no longer behaves as a liquid and can be handled as a solid material. Sludge, or residual solids, is the end product of wastewater treatment, whether biological or physicalchemical treatment. Activated sludge treatment process concept and system design dr. The principal secondary treatment techniques used in secondary treatment are the trickling filter and the activated sludge process. For each type of sludge and pumping application a different type of pump may be needed. Municipal wastewater and sludge treatment at municipal wastewater treatment plants in the united states, raw municipal wastewater undergoes preliminary, primary, secondary, and in some cases, additional treatment to yield treated effluent and a concentrated stream of solids in liquid, called sludge. Sludge, which constitutes 1% of wastewater entering the plant, is digested anaerobically and dehydrated. This residue is commonly classified as primary and secondary sludge. Although typical quantities of domestic wastewater generation are somewhat predictable, industrial contributions are more varied. The residue that accumulates in sewage treatment plants is called sludge or biosolids. One possibility for fs treatment is cotreatment with sewerbased wastewater treatment technologies.
This paper will discuss the types of microbiological problems that can occur in activated sludge operation. One possibility for fs treatment is co treatment with sewerbased wastewater treatment technologies. The activated sludge is then separated from the liquid by clarification. Wastewater sludge treatment and disposal have always created more problems than wastewater treatment itself. As a suspendedgrowth biological treatment process, activated sludge utilizes a dense microbial culture in suspension to biodegrade organic material under aerobic. Sand, eggshells and other coarse inorganic material is present in the flow in addition to organic matter from household, industrial, commercial and institutional water use. Emerging technologies for wastewater treatment and inplant. Act clean water act cwa, municipal wastewater treatment facilities have been designed and built or upgraded to abate an everincreasing volume and diversity of pollutants. Bod mgl tank may 8 2,710 900 140 84 140 1,100 may 15 3,560 966 357 120 150 1,210 may 22 3,460 712 260 140 924 thickener may 29 3,820 dehydrator 694 143 dewatered cake 120 969 efl. Sludge produced in wastewater treatment plants must be conveyed from point to point in the plant in conditions ranging from a watery sludge to a thick sludge. While many industries treat wastewater onsite, it is not unusual for a publicly owned wastewater treatment plant potw in an industrialized city to treat wastewater comprised of up to 40 % industrial wastewater.
The activated sludge excess biomass or cell mass removed from the secondary treatment process. Typical concentrations of other constituents in wastewater treatment plant effluent are summarized in chapter 2. Preliminary treatment of wastewater generally includes those processes that remove debris and coarse biodegradable material from the waste stream andor stabilize the wastewater by equalization or chemical addition. After a certain amount of time, the activated sludge is allowed to settle out by sedimentation and is disposed of wasted or reused returned to the.