Introduction

Natural wastewater treatment refers to a category of technologies that specifically and substantially utilize natural methods to reduce contaminants from wastewaters in large open fields without incurring the cost of energy-intensive mechanical equipment operations for major treatment responses. The natural wastewater treatment systems have enjoyed a revival, not only in developing countries, but also in the United States the impetus for this renewed interest in natural systems for our residual...

Fluid Flow Rate and Mass Loading

Almost all wastewater treatment plants are designed based on the annual average daily flow rate of wastewater being processed. However, it should be noted that every plant has to take into account the actual daily flow rate, characteristics of wastewater, and the combination of flow rate and composition (called mass-loading) of the wastewater steam. In an on-site wastewater treatment facility that deals with wastewater streams from a fixed food processing operation, flow rate and mass-loading...

Dewatering

Dewatering of sludge is a physical unit operation to reduce the moisture of the sludge in preparation for subsequent further treatment processes. As the agricultural use of the sludge and landfilling are increasingly restricted in the United States and elsewhere, drying and incineration are widely implemented. As a result, the costs related to the treatment of sludge have considerably risen and commonly represent 35-50 of the total operating costs of the wastewater treatment. Reducing the...

Kinetics and Reaction Rates

Chemical or biochemical kinetics is the study of chemical or biochemical reactions with respect to reaction rates, effect of conditions reactions are subject to, rearrangement of molecules, formation of intermediates, and involvement of catalyst. The word kinetics is originated from the Greek kinesis, meaning movement. Thus, the kinetics of chemical or biochemical reactions are mainly concerned with rate of reaction and anything else affecting it. In general, the reaction rate depends on the...

Advanced Wastewater Treatment Processes

Biological treatment processes, in combination with primary sedimentation, typically remove 85 of the BOD5 and soluble solids originally present in the raw wastewater and some of the heavy metals. Activated sludge generally produces an effluent of slightly higher quality, in terms of these constituents, than trickling filters or RBCs. When coupled with a disinfection step, these processes can provide substantial but not complete removal of bacteria and virus. However, they remove very little...

Estimating the Unit Cost of Treating Food and Agricultural Wastewater

Cost estimation of a yet-to-be-built wastewater treatment facility is difficult as an engineer or process designer, your responsibility is not to try to outsmart the experts that are hired to do cost forecasting if a decision of building a specific design of wastewater treatment facility is finalized rather, your job is to estimate the total costs of a particular wastewater project in order to compare the one under the study to other treatment management alternatives or options. The estimation...

Physicochemical Removal of Nitrogen

As described previously, biological nitrogen removal is not the only technology available for nitrogen compound removal from wastewaters. Some nonbiological processes are able to recover nitrogen compounds in their dissolved forms for potential uses as fertilizers and are viable alternatives under some circumstances. On the whole, however, physicochemical processes for removing nitrogen from wastewater are not practically popular. The reasons for the unpopularity are often cited as cost,...

Coagulation and Flocculation

Many substances in wastewater vary greatly in size, from a few angstroms for soluble solids to a few hundred microns of suspended materials. Consider a force balance upon a clay particle with diameter of 1 micron in the absence of electrostatic forces, the terminal settling velocity of this particle in water is approximately 10 4 cm s based on the following expression (Equation 3.6) where (ps pf) is the density difference between the particle and fluid (water), and is the viscosity of the fluid...

Physicochemical Removal of Phosphate

There are several physicochemical phosphate removal processes that can be used with conventional secondary wastewater treatment. These processes generally involve using chemicals to facilitate precipitation of phosphate and a primary clarifier (sedimentation tank or basin) to separate phosphate-containing sludge from the treated wastewater or in some cases, dissolved air flotation is used to remove the phosphorus-containing complexes. The principal chemicals employed in this type of removal are...

Recoverable Aroma Flavoring Compounds from Food Processing Wastewaters

Recovery of flavors and savory compounds from food wastewaters has long been contemplated however, it was not economically and technically possible (with few exceptions) until the advent of membrane-based technologies. Today, pervaporation technology has been used successfully for recovering flavor products from fermentation broth in bioreactors and for aroma recovery (Trifunovic and Tragardh, 2002 Peng and Liu, 2003). Wastewaters from fruit and vegetable processing operations, in particular,...

Wetland Systems

Natural wetlands (e.g., swamps, bogs, marshes, fens, sloughs, etc.) are long recognized as providing many benefits, including food and habitat for wildlife, water quality improvement, flood protection, shoreline erosion control, and opportunities for recreation and aesthetic appreciation. Many of these same benefits have been realized by projects across the country, which involve the use of wetlands in wastewater treatment. Wetlands are constructed as either surface flow (see Fig. 6.10) or...

Trickling Filter TF

Trickling filters (also called biofilters) have been used to remove organic matter from wastewater for nearly 100 years. The TF is an aerobic treatment system that utilizes microorganisms attached to a medium to remove organic matter from wastewater. The colonies of microorganisms attached to solid surfaces are called biofilms due to their thin layers of biological structures. This type of system is common to a number of biological wastewater technologies, such as rotating contactors and packed...

Filtration Processes

Filtration is often employed in wastewater treatment, with or without prior treatments by coagulation-flocculation and sedimentation, for removal of flocs (or bioflocs) from primary and secondary wastewater treatment processes, solids remaining in effluents from primary and secondary wastewater treatment processes, and precipitates from physicochemical treatment of phosphate from the advanced wastewater treatment stage. Earlier applications of filtration for wastewater treatment borrowed...

Biological Removal of Phosphorus

Phosphorus is a constituent of wastewater, averaging around 10 mg liter in most cases. The principal form in food and agricultural wastewater is organically bound phosphorus. Organically bound phosphorus originates from body and food waste and, upon biological decomposition of these solids, is converted to orthophosphates. Biological phosphate removal is a relatively new technology dating back to the late 1950s it wasn't until the 1970s that there were full-scale processes developed for...

Membrane Separations

Membrane separations have been playing an increasing role in wastewater treatment this is the most evident in processing whey wastewater with ultrafiltration in the dairy industry, one of many types of membrane separation technologies, and in membrane pervaporation of volatile organic compounds (VOCs) from wastewater. Currently, a new field of membrane separations called nanomembrane technology is said to be the future nano-technology for achieving clean water with this purported type of smart...

Equalization Basins

Generally speaking, flow equalization is not a treatment process or treatment method it's a method to improve wastewater treatment processes, whether they are physicochemical processes or biological processes. The purpose of flow equalization is to balance out the process parameters, such as flow rate, organic loading, strength of wastewater streams, pH, and temperature over a 24-hour period. This practice is often applied either at the very beginning of the wastewater treatment plant aiming at...

Recoverable Carbohydrates Fats and Proteins for Human and Animal Consumption

Currently, whey proteins are recovered from liquid whey for both human consumption and animal feed in limited quantities in the dairy industry. Whey proteins have found uses in infant formulae, in health foods, and in Table 8.2. Potential products from wastewaters generated from different food-processing sectors of the food industry. Offal, blood, soluble proteins, DAF sludge Spent brewer's yeast, starch, and waste grains Trimmings, fruit pomace, and flavors Beverage spills, wine grape...

Material Balances and Stoichiometry

In dealing with food and agricultural wastewater, whether formulating treatment and utilization strategy or planning the initial stage of a comprehensive management project, a basic understanding of the effects of mass flow rate or loading factors on process designs is essential. Stoichiometry is the material accounting for a chemical reaction. Given enough information, one can use stoichiometry to calculate masses, moles, and percents within a chemical equation that is an expression of a...

Important Microorganisms in Wastewater Bacteria and fungi

Bacteria are the most important and the largest components of the microbial community in all biological wastewater treatment processes. Depending on the biological process and pH, the number concentration of bacteria is different, with activated sludge (aggregates of healthy aerobic bacteria living in colonial structures called flocs) having the largest number concentration of bacteria. Bacteria range in size from approximately 0.5 to 5 m and take one of four major shapes sphere (cocci),...

Sludge Quality and Characteristics

Sludge is rather complex material, both in the sense of its composition and in the characteristics of its fluid dynamics, which are shaped by its moisture content and interactions between water molecules and other solid particles. In general, when the moisture content of the sludge exceeds 90 by mass or weight, the sludge behaves as a Newtonian fluid, whereas below 90 it behaves as a non-Newtonian fluid in a way similar to those of some polymers (both certain biopolymers such as foods and...

Characteristics of Agricultural and Food Wastewater

Manufacturing Sauerkraut Flow Chart

Whenever and wherever food, in any form, is handled, processed, packed and stored, there will always be an unavoidable generation of wastewater. Wastewater is the most serious environmental problem in the manufacturing and processing of foods. Most of the volume of wastewater comes from cleaning operations at almost every stage of food processing and transportation operations. The quantity and general quality (i.e., pollutant strength, nature of constituents) of this processing wastewater...

Land Treatment Systems

Land application of wastewater is perhaps the oldest method for disposal and treatment of wastewaters. Early systems were used in England as Land Farms, which received untreated wastewater and night soil from nearby communities. Today, land application systems have included application to edible and nonedible crops, to rangelands, to forests and wood plantations, to recreational areas including parks and golf courses, and to disturbed lands such as mine spoil sites. Land application of...

Sedimentation

Sedimentation is the most common physical unit operation in wastewater treatment, more so in primary treatment where sedimentation is the workhorse of the treatment. The term sedimentation is also called settling in some literature. Sedimentation is, in a nutshell, a process by which the suspended solids, which have higher densities than that of water, are re- Figure 3.5. A photo of a dissolved air flotation system. Figure 3.5. A photo of a dissolved air flotation system. moved from wastewater...

Rotating Biological Contactor RBC

Rotating Biological Contactors (RBCs) are used in the treatment of wastewater as a secondary treatment process. The RBC process involves allowing wastewater to come in contact with a biological medium in order to remove contaminants in sewage before discharge of the treated wastewater to the environment, usually a river. The construction of an RBC consists of a series of plastic discs, the media, mounted on a driven shaft that is contained in a tank or trough. Commonly used plastics for the...

Ion Exchange

Ion exchange is a process in which ions of a particular species in solution are replaced by ions with a similar charge but of different species attached to an insoluble resin. In essence, ion exchange is a sorption process and can also be considered a reversible chemical reaction. The common appli cations of ion exchange are water softening (removal of hardness ions such as CA2+ and Mg2+) and nitrate removal in advanced wastewater treatment operations. These ion exchange resins are either...

Sludge Stabilization

Once the sludge is thickened, two options are available for further treatment of the concentrated sludge. It can be dewatered to a solid content of between 30-40 or it can undergo stabilization processes to reduce the organic materials in the sludge before going to the dewatering step. Coarse primary solids and secondary sludge (sometimes called biosolids) accumulated in a wastewater treatment process must be treated before disposal to ensure environmentally responsible and lawful outcome....

Combined Aerobic Processes

The combined aerobic processes are designed to sustain shock loads in activated sludge, aerobic contactor, and trickling filter (biofilter) processes. There are several possible combinations of these aerobic processes activated biofilter process, trickling filter solids-contact process, biofilter activated-sludge process, and trickling filter-activated sludge process. The activated biofilter process is a trickling filter with recycling of secondary sludge back to the trickling-filter to create...

Floating Aquatic Plant Systems

Aquatic plant systems are engineered and constructed systems that use aquatic plants in the treatment of industrial or domestic wastewater. They are designed to achieve a specific wastewater treatment goal. Aquatic plant systems can be divided into two categories Systems with floating aquatic plants such as water hyacinth, duckweed, Systems with submerged aquatic plants such as waterweed, water milfoil, and watercress The use of aquaculture as a means of treating wastewater involves both...

Biological Removal of Nitrogen Nitrification and Denitrification

The goal of nitrogen removal, regardless of what exactly forms of nitrogen compounds in wastewater streams, has been the production of nitrogen gas, an inert, water-insoluble gas that is easily separated from liquid media. The necessity of producing nitrogen gas in the treatment processes of nitrogen removal is mainly due to high solubility of nitrogen compounds such as NO3 , NH4+, and NO2 present in the nitrogen removal. There is some indication that this old paradigm is being challenged....

Completely Mixed Aerated Lagoon CMAL

Lagoons are one of the oldest wastewater treatment systems created by mankind. They consist of lined in-ground earthen basins in which the wastewater is detained for a specified time (detention time) and then discharged. The size and depths can vary, as well as the degree of treatment. Although these lagoons, or ponds as they are sometimes called, are very simple in design, there are complex chemical, biological and physical processes occurring. There are five main types of lagoons facultative...

Denitrification

Denitrification can be viewed in some ways as a reversal of nitrification however, although the denitrification does go through a two-step biochemical transformation, the end product of the denitrification is not ammonia or organic nitrogen rather, it is inert gaseous nitrogen Liu et al., 2003 . Denitrification can only be operated under anoxic conditions when the free oxygen level is very low, but not necessarily zero, and when a carbon source, such as methanol or settled sewer which has low...

Stabilization Ponds

Anaerobic Ponds Wastewater Treatment

One of the ancient wastewater treatment technologies, the stabilization pond also referred to as a lagoon , has been used continuously as a method of sewage disposal. In some cases, these ponds were also utilized for aquaculture. Stabilization ponds are used for both municipal waste-water treatment and industrial wastewater treatment, particularly for wastewaters from small communities and seasonal industrial wastewaters as well as less affluent communities throughout the world Fig. 6.1 ....

Sludge Thickening Concentration

Gravity Sludge Thickener Diagram

Further sludge concentration is first accomplished by the use of thickening equipment that will increase the solids content to between 2 and 5 . Sludge thickening is achieved through one of two means flotation and settling to the bottom by gravity or centrifugal force. The thickening operation separates water from the sludge as much as possible and is cost-effective because the cost involved in the process is well offset by the savings gained through the reduction of sludge volume, which...

Membrane Processes for Advanced Wastewater Treatment

An overview about membrane processes that can be used in wastewater treatment has been presented in Chapter 3 the general characteristics of various processes determine the applications of membrane processes in wastewater treatment. Membrane filtration can theoretically replace conventional processes such as secondary sedimentation, flocculation, settling basin, and granular filtration all together. In reality, however, the applications of membrane filtration in wastewater treatment are...