Final Settling Tank Clarifier Observations

Settling tank observations include flow pattern (normally uniform distribution), settling, amount, and type of solids leaving with the process effluent (normally very low) and the clarity or turbidity of the process effluent (normally very clear). Observations should include the following conditions Sludge bulking Solids are evenly distributed throughout the tank and are leaving over the weir in large quantities. Sludge solids washout Sludge blanket is down but solids are flowing over the...

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...

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

Sulphur Cycle Ecosystem

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...