Dissolved Oxygen Concentration Test
The dissolved oxygen (DO) concentration test is a form of measurement carried out on water or wastewater sample to determine the oxygen content in the sample. The DO concentration test can be conducted on still water, such as in a wastewater plant or lake, or in moving water, such as in a stream. The DO concentration is measured as mg/L. The DO concentrations in water enables the organisms which respire aerobically to thrive. Such organisms respire massively in the presence of biodegradable matter in water, which may strain the DO concentration. Due to the significance of the DO concentration in aquatic organisms, DO concentration test has multiple benefits especially on the determination of the effects of pollution on such organisms. When the DO concentration test is carried out in a stream from an effluent discharge at intervals downstream, a DO sag curve is obtained. The DO sag curve is important in the determination of the estimated point at which the DO levels will either be depleted or at unsustainable levels. If the pollutant will significantly strain the DO levels in the stream, then it will require to rerouting to a treatment plant prior to discharging into the stream. In the treatment plant, DO concentration test is important in monitoring the degradation of organic materials which would otherwise strain the DO levels downstream.

BOD Test
The biochemical oxygen demand (BOD) test is a form of measurement undertaken in a stream or treatment plant to determine the amount of DO used up in the degradation process. Unlike the DO concentration test, the BOD test is carried out as a simulation of the actual treatment and stream water conditions. The simulation takes several days where the water sample containing biodegradable organic matter is incubated with the microorganisms which are responsible for the degradation process. After the incubation period, the DO consumed by the microorganism in the degradation process is measured and registered as BOD. The BOD refers to the pollution strength of a water sample or the content of biodegradable organic matter of a water sample. The BOD is measured as mg/L.
The BOD test is beneficial to the state and federal regulations in multiple ways. Firstly, the BOD test enables the regulation to monitor and control the amount of biodegradable organic matter discharged into a stream to avoid straining the DO concentration downstream. Furthermore, the BOD test enables the regulations to determine the level of treatment required, especially the content of DO required for a particular effluent. The BOD test also determines the efficiency of a treatment plant by comparing the amount of incoming and outgoing biodegradable organic matter in the plant. Finally, the BOD test enables the determination of the strength of raw pollution which is an important parameter of enacting regulations on organizations responsible for the discharge.

Microbiology Tests
The microbiology tests are those set of procedures intended to test for the presence of coliforms in a water sample. Coliforms are bacteria which thrive well in the intestinal tracts of humans and other warm-blooded organisms. Among other pathogens, coliforms are more resistant to disinfectants and hence require a higher dose of disinfectants. Types of water disinfection include ultraviolet radiation, ozonation, and chlorination. Once coliforms are finally killed, it is assumed that all the other pathogens are killed since they cannot withstand the high dose of disinfectant required to eliminate coliforms. The microbiology tests are therefore designed to detect any form of coliform in a water sample. However, different regulations such as the National Safe Drinking Water Act (NSDWA), Environmental Protection Agency (EPA), and National Pollutant Discharge Elimination System (NPDES) have set the maximum acceptable coliform count in a water and wastewater. Among the various microbiology tests include the membrane filter techniques (MF), multiple-tube fermentation technique (MTF), presence-absence test (P-A), and minimal media ONPG-MUG test.

The microbiology tests in form of coliform tests have a range of benefits relating to water and wastewater treatment. Firstly, microbiology tests indicate whether disinfection of water and wastewater in treatment plants is necessary by detecting fecal contamination. Secondly, negative coliform test after water disinfection ascertains that the water is free from pathogens. Furthermore, the ease of identification of coliforms through a range of approaches means that a coliform tests is an effortless approach to pathogen detection in water treatment.

Suspended Solid Test
Suspended solids test are those set of procedures used to determine the content of the non-filterable residue per unit volume of a water and wastewater sample. The non-filterable residue includes all particles that are unable to pass through a filter paper. Most of the non-filterable solids are organic materials consisting of food remains fecal materials and bacteria. The larger suspended solids are removed through gravity settling while the smaller solids are screened. The optimal filter paper for the suspended solid test is prescribed in the Standard Methods procedure. The solids that remain on the filter paper are separated from residual water through drying to obtain the dry mass of solid referred to as the total suspended solids (TSS). The total suspended solids are measured in mg/L. In a related test, the mixed liquor suspended solid test (MLSS) determines the approximate population of microbes in a mix of microbes and wastewater. Among the benefits of the suspended solid tests includes prevention of oxygen stresses downstream as organic most organic materials are filtered before releasing the water to the stream. Also, suspended solids prevent light to penetrate to the bottom of the river where a variety of river ecosystem thrives. Through the suspended solid test, the massive solids which are responsible for blocking sunlight are eliminated. The estimation of the population of microbes in the mixed liquor suspended solid test is important in the determination of correct activated sludge mixture.

Fixed and Volatile Test
The fixed and volatile test supersedes the suspended solid test by working on the TSS. In the fixed and volatile test, the TSS is taken into a muffle furnace which heats the solids to temperatures of up to 600 degrees Celsius. The higher temperatures enable the solids to undergo thermal decomposition where the carbon-rich solid break down to form water and carbon dioxide. Once the solids undergo the thermal decomposition, they are said to be volatilized. As in any form of thermal breakdown, residuals remain in the glass fiber filter. The content of the residuals is referred to as the fixed suspended solids (FSS) and is measured in mg/L. The amount of product which escapes as either carbon dioxide, water vapor or other gases is referred to as the volatile suspended solids (VSS), also measured in mg/L. The amount of VSS is obtained experimentally from the differences in the amount of TSS and FSS. The fixed and volatile tests are primarily important in the characterization of a TSS sample. It would be beneficial to the federal and state entities to determine the organic and inorganic content of TSS are released to the municipal wastewater treatment facilities for regulation purposes. The tests can also be alternatively used to measure the content of the microbial cell mass through the mixed liquor volatile suspended solids, where the volatilized content is assumed to be the microbial cell mass.