Activated Sludge Process Equipment

The equipment requirements for the activated sludge process are more complex than other processes discussed. Equipment includes an aeration tank, aeration, system settling tank, return sludge, and waste sludge. These are discussed in the following. The aeration tank is designed to provide the required detention time (depends on the specific modification) and ensure that the activated sludge and the influent wastewater are thoroughly mixed. Tank design normally attempts to ensure that no dead...

Pump Control Systems

Pump operations usually control only one variable flow, pressure, or level. All pump control systems have a measuring device that compares a measured value with a desired one. This information relays to a control element that makes the changes. The user may obtain control with manually operated valves or sophisticated microprocessors. Economics dictate the accuracy and complication of a control system. Most centrifugal pumps require some form of pump control system. The only exception to this...

Weight Concentration and Flow

Using Table 4.1 to convert from one unit expression to another and vice versa is good practice however, when making conversions to solve process computations in wastewater treatment, we must be familiar with conversion calculations based upon a relationship among weight, concentration, and flow or volume. The basic relationship is Weight Concentration x Flow or Volume x Factor (4.1) Table 4.2 summarizes weight, volume, and concentration calculations. With practice, many of these calculations...

Chapter Review Questions

14.1 What type of waste treatment pond is most common 14.2 Give three classifications of ponds based on their location in the treatment system. 14.3 Describe the processes occurring in a raw sewage stabilization pond (facultative). 14.4 How do changes in season affect the quality of the discharge from a stabilization pond 14.5 A wastewater treatment pond has an average length of 690 ft with an average width of 425 ft. If the flow rate to the pond is 300,000 gpd and it is operated at a depth of...

Sulfur Cycle

Bioaccumulation Chojnacka

Sulfur, like nitrogen, is characteristic of organic compounds. The sulfur cycle is both sedimentary and gaseous (see Figure 8.19). The principal forms of sulfur that are of special significance in water quality management are organic sulfur, hydrogen sulfide, elemental sulfur, and sulfate (Tchobanoglous and Schroeder, 1985). Bacteria play a major role in the conversion of sulfur from one form to another. In an anaerobic environment, bacteria break down organic matter, thereby producing hydrogen...

Biochemical Oxygen Demand Testing

Biochemical oxygen demand (BOD) measures the amount of oxygen consumed by microorganisms in decomposing organic matter in streamwater. BOD also measures the chemical oxidation of inorganic matter (the extraction of oxygen from water via chemical reaction). A test is used to measure the amount of oxygen consumed by these organisms during a specified period of time (usually 5 days at 20 C). The rate of oxygen consumption in a stream is affected by a number of variables temperature, pH, the...

Cyclone Degritter

The cyclone degritter uses a rapid spinning motion (centrifugal force) to separate the heavy inorganic solids or grit from the light organic solids. This unit process is normally used on primary sludge rather than the entire wastewater flow. The critical control factor for the process is the inlet pressure. If the pressure exceeds the recommendations of the manufacturer, the unit will flood and grit will carry through with the flow. Grit is separated from the flow and discharged directly to a...

Bacteria

The simplest wholly contained life systems are bacteria, or prokary-otes, which are the most diverse group of microorganisms. As mentioned, they are among the most common microorganisms in water. They are primitive, unicellular (single-celled) organisms that possess no well-defined nucleus and present a variety of shapes and nutritional needs. Bacteria contain about 85 water and 15 ash or mineral matter. The ash is largely composed of sulfur, potassium, sodium, calcium, and chlorides, with...

Suction Specific Speed

Suction specific speed (Nss), another impeller design characteristic, is an index of the suction characteristics of the impeller (i.e., the suction capacities of the pump) (Wahren, 1997). For practical purposes, Nss ranges from about 3000 to 15,000. The limit for the use of suction specific speed impellers in water is approximately 11,000. The following equation expresses Nss rpm revolutions per minute. Q flow in gpm. NPSHR net positive suction head required. Ideally, Nss should be...

Anaerobic Digestion

Anaerobic digestion is the traditional Key Point In an anaerobic digester, the method of sludge stabilization. It involves entrance of air should be prevented because , , , ,. ,, , air mixing with the gas produced in the using bacteria that thrive in the absence of digester could create an explosive mixture. oxygen. It is slower than aerobic digestion but has the advantage that only a small percentage of the wastes are converted into new bacterial cells. Instead, most of the organics are...

Nematodes and flatworms worms

Tubificid Worms

Along with inhabiting organic mud, worms also inhabit biological slimes they have been found in activated sludge and in trickling filter slimes (wastewater treatment processes). Generally microscopic in size, they can range in length from 0.5 to 3 mm and in diameter from 0.01 to 0.05 mm. Most species have a similar appearance. They have a body that is covered by cuticle, cylindrical, nonsegmented, and tapered at both ends. These organisms continuously enter wastewater treatment systems,...

Settled Sludge Volume Settleability

Settled sludge volume (SSV) is determined at specified times during sample testing (e.g., 30- and 60-minute observations). Normal operation When the process is operating properly, the solids will settle as a blanket (a mass), with a crisp or sharp edge between the solids and the liquor above. The liquid over the solids will be clear, with little or no visible solids remaining in suspension. Settled sludge volume at the end of 30 to 60 minutes will be in the range of 400 to 700 mL. Old or...

Surface Loading Rate Surface Settling Rate and Surface Overflow Rate

The surface loading rate is the number of gallons of wastewater passing over 1 ft2 of tank per day. This can be used to compare actual conditions with design. Plant designs generally use a surface loading rate of 300 to 1200 gpd ft2. Other terms used synonymously with surface loading rate are surface settling rate and surface overflow rate. Surface Settling Rate (gpd ft2) -Flow (gpd)-2 (13.1) Problem A settling tank is 120 ft in diameter, and flow to the unit is 4.5 MGD. What is the surface...

Inorganic Substances

Several inorganic components are common to both wastewater and natural waters and are important in establishing and controlling water quality. Inorganic load in water is the result of discharges of treated and untreated wastewater, various geologic formations, and inorganic substances left in the water after evaporation. Natural waters dissolve rocks and minerals with which they come in contact. As mentioned, many of the inorganic constituents found in natural waters are also found in...

Nitrogen Cycle

Figure Nitrogen Cycle Bacteria

Nitrogen is an essential element required by all organisms. In animals, nitrogen is a component of crucial organic molecules, such as proteins and DNA, and it constitutes 1 to 3 dry weight of cells. Our atmosphere contains 78 by volume of nitrogen, yet it is not a common element on Earth. Although nitrogen is an essential ingredient for plant growth, it is chemically very inactive, and it must be fixed before the vast majority of the biomass can incorporate it. Special nitrogen-fixing bacteria...

Biogeochemical Cycles

Combine Biogeochemical Cycles

Several chemicals are essential to life and follow predictable cycles through nature. In these natural cycles, or biogeochemical cycles, the chemicals are converted from one form to another as they progress through the environment. The water wastewater operator should be aware of the cycles dealing with nutrients (i.e., carbon, nitrogen, and sulfur) because they have a major impact on the performance of the plant and may require changes in operation at various times of the year to keep them...