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...

Population Equivalent or Unit Loading Factor

When a wastewater characterization study is required, pertinent data are often unavailable. When this is the case, population equivalent or unit per capita loading factors are used to estimate the total waste loadings to be treated. If we know the BOD contribution of a discharger, we can determine the loading placed upon the wastewater treatment system in terms of equivalent number of people. The BOD contribution of a person is normally assumed to be 0.17 lb BOD day. To determine the population...

DPD Spectrophotometric

The DPD indicator reacts with chlorine to form a red color. The intensity of the color is directly proportional to the amount of chlorine present. This color intensity is measured using a colorimeter or spectro-photometer. This meter reading can be converted to a chlorine concentration using a graph developed by measuring the color intensity produced by solutions with precisely known concentrations of chlorine. In some cases, spectrophotometers or colorimeters are equipped with scales that...

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...

Process Control Calculations for Filter Presses

As part of the operating routine for filter presses, operators are called upon to make certain process control calculations. The one most commonly used when operating the belt filter press determines the hydraulic loading rate on the unit, and the most commonly used process control calculation for plate and filter presses determines the pounds of solids pressed per hour. Both of these calculations are demonstrated below. 17.5.8.1.1 Belt Filter Press Hydraulic Loading Rate Example 17.28 Problem...

Calculating NPSHA

In the following two examples, we demonstrate how to calculate NPSHA for two real-world situations (1) determining NPSHA for an open-top water tank or a municipal water storage tank with a roof and correctly sized vent, and (2) determining the NPSHA for a suction lift from an open reservoir. The following calculation may be used for an open-top water tank or a municipal water storage tank with a roof and correctly sized vent, as shown in Figure 10.4 and Figure 10.5. The formula for calculating...

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...

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...