Manchester utilizes various processes for BOD/COD reductions - from filtration to advanced oxidation systems including reactors with intense aerobic or anaerobic biological activity. Manchester systems are selected on the basis of achieving the minimum cost system to meet customer discharge requirements. The Organic Destruction Module (ODMTM) provides much higher BOD/COD removal rates than other biological processes. Anaerobic industrial processes are usually utilized for high concentration of BOD/COD (>10,000 mg/L).

APPLICATIONS:

BOD/COD Treatment Systems – Complete systems to meet customer goals using advanced electronic monitoring and controls. Manchester utilizes systems from conventional activated sludge, extended surface packing for aerobic and anaerobic systems to specialized advanced oxidations utilizing ozone or peroxide, dissolved air flotation etc. and others depending on the application.

Retrofit Existing Non-Performing Systems – Retrofit requires examination of existing data and potentially additional analytical data to achieve a system with increased expanded BOD/COD removals.

SYSTEMS:

Biological

The BOD removal efficiency of aerobic biological treatment processes depends on a number of factors including (but not limited to): influent BOD loading, nutrient to biological mass (FM) ratio, temperature, nutrient levels and dissolved oxygen (DO) concentrations. The treatment facility may use aeration or other oxygen sources such as pure oxygen, hydrogen peroxide (H2O2), or ozone (O3) to supplement DO levels when oxygen-limited conditions in aeration tanks result in poor BOD removals. These conditions can be brought about by unexpected peaks in influent BOD loading, seasonal variations in BOD loading, facility downtimes where unfed bacteria die off; hot weather (which reduces the efficiency of oxygen transfer by mechanical aeration equipment) and other in-plant process upsets.

Advanced Oxidation Systems

Advanced Oxidation Systems have typically utilized ozone, peroxide or hydroxyl ions to decompose the more difficult species to break down. These systems may be coupled with ultraviolet (UV) light and potentially catalysts to enhance the oxidation rates. These systems are typically less in capital cost than biological systems but have a much higher operation cost.

Note: When measuring the BOD or COD of enriched oxygen waters, especially in H2O2 treated wastewaters, it is important to determine the residual H2O2 concentration prior to analysis. This is because H2O2 will interfere with both of these analytical methods. In the standard BOD test, residual H2O2 in the sample will liberate oxygen over the test period, resulting in a "false low" BOD value. In the standard COD test, residual H2O2 will react with the potassium dichromate reagent, resulting in a "false high" COD value.

CONTROLS

Manchester recommends sufficient controls to enable automatic recordkeeping of various process parameters: DO, pH, ORP to mention a few. We are a system integrator for multiple PLC manufacturers and graphic interfaces in addition to being a UL508 system fabricator. The graphical interfaces allow process trending and recording of multiple system parameters. With the installation of a Manchester Control System our personnel can periodically interrogate the system from a remote location to assist in continuous system evaluations and troubleshooting. (See Control Systems)

MANCHESTER SYSTEMS

Manchester recommends the use of the most economical system to achieve customer performance goals. However we will furnish a system to customer or other engineered specification that are the most competitive in the industry when comparing quality and performance.

DEFINITIONS

To measure oxygen demand, the biochemical oxygen demand (BOD) method relies on bacteria to oxidize readily available organic matter during a five-day incubation period. In contrast, chemical oxygen demand (COD) methods use strong chemicals to oxidize organic matter.

BOD - The biochemical oxygen demand (BOD) test most closely models aerobic waste treatment and it measures oxygen taken up during the oxidation of organic matter. The most common test runs for a five-day period (BOD5), but can run longer, depending on specific sample circumstances.

BOD testing has its widest application in measuring waste loadings of treatment plants, and in evaluating the efficiency of treatment processes. It is of limited use in industrial wastewaters containing heavy metal ions, cyanides, and other substances toxic to microorganisms.

COD - Although COD is comparable to BOD, it actually measures chemically oxidizable matter. The COD test is not a direct substitute for the BOD test; however, a ratio usually can be correlated between the two tests. This requires COD versus BOD testing over a specified period of time.

Generally, COD is preferred to BOD in process control applications, because results are more reproducible and are available in a few minutes or hours rather than five days. In many industrial samples, COD testing may be the only feasible course because of the presence of bacterial inhibitors or chemicals that will interfere with a BOD determination. Many industrial customers find that parallel COD and BOD testing is beneficial because the COD test can be used to target a specific BOD range, eliminating the need for multiple BOD dilutions.