What is Oxidation Ditch?
Oxidation ditch is a particular type of extended aeration process, where aeration tank is constructed in the ditch shape (oval shape). It is a modified activated sludge biological treatment process that makes use of long solid retention times to remove biodegradable organic matter.
Oxidation ditches are commonly made of impervious material such as reinforced concrete, asphalt and clay. The oxidation ditch process is a secondary wastewater treatment technology, applicable in any situation where activated sludge treatment (conventional or extended aeration) is appropriate. Oxidation ditches are providedin wastewater treatment plants that require nitrification of effluent because the oxidation basins can be sized using an appropriate SRT to achieve nitrification. This technology is effective and finds its application in small installations, small communities, and isolated institutions, because it requires more land than conventional treatment plants.
Typical oxidation ditch treatment system consists of-
Basin:The aeration tank consists of a single or multi-channel configuration within a ring shaped basin 1.0 to 1.5 m deep through which the wastewater flows and of suitable width forming a trapezoidal or rectangular channel cross-section.
Bar screens: Preliminary treatment such as bar screens normally precedes the oxidation ditch.
Surface aerators: An aeration rotor, such as brush rotors, disc rotors or fine bubble diffusers is placed across the ditch to provide aeration and wastewater circulation at velocity of about 0.3 to 0.6 m/s. The aeration increases the dissolved oxygen concentration. The horizontal or vertically mounted mechanical aerators are used to provide circulation, oxygen supply, aeration and at the same time, to provide sufficient horizontal velocity for not allowing the cells to settle at the bottom of the oxidation ditch.
The oxidation ditch can be operated as an intermittent type with fill and draw cycles consisting of:
(a) Inlet valve and outlet value;
(b) Stoppingaeration and circulation device;
(c) Sedimentation tank to settle the sludge. This settled sludge then gets re-circulated to maintain necessary MLVSS in the oxidation ditch. The sludge generated in oxidation ditch is less and can be directly applied to the sand-bed for drying.
Advantages and disadvantages of Oxidation Ditch
In this section, we will guide you through various advantages and disadvantages of using an oxidation ditch system.
Advantages of Oxidation Ditch
The main advantages of the oxidation ditch is that it can commonly be installed as ‘fit and forget’ technology with low operational requirements and maintenance costs. Some of the advantages of oxidation ditches include:
i) This process is reliable over other biological treatment processes owing to a constant water level and continuous discharge;
ii) Resilient to the impact of shock load or hydraulic surge due to long hydraulic retention time and complete mixing;
iii) Production of less sludge than other biological treatment processes. Only 15% of original BOD ends up as sludge;
iv) Energy efficient operations results in reduced energy costs;
Disadvantages of Oxidation Ditch
i) Suspended solids concentrations of wastewater are relatively higher;
ii) Requires a larger land area, limiting the feasibility of oxidation ditches in urban, suburban, or other areas where land acquisition costs are relatively high.
Oxidation ditches are installed at significantly lower operation and maintenance costs than other secondary treatment processes. As compared to other treatment technologies, in oxidation ditch energy requirements are less, operational attention is minimal, maintenance is easy and chemical addition is not usually required. The cost of an oxidation ditch system depends on land, plant size, construction costs, and other site specific factors.
How can Netsol Water help you?
Netsol Water is one of the leading water and wastewatertreatment company in India with services in the field of WTP manufacturing, WWTP manufacturing, STP manufacturing, among other services. The company designs and manufactures all in one systems that are ideal for treating wastewater and the sludge generated and not only turns your wastewater into usable water but also acts as a savior of Mother Earth and its precious resource “water”.
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