Types of WasteWater Treatment Ponds - Types of Ponds

Based upon the range of biological reactions occuring in pounds there are three types of ponds.

Aerobic (high-rate) pond in which there is no significant anaerobic or slndge zone.

Anaerobic ponds, in which the conlribution of any possible aerobic suface layer is small.

Oxidation ponds (so called facultative or aerobic anaerobic pond in which have the whole range of reaction is present. this is predominant type of pond in municipal wn.

Aerobic ponds:

These cause odor problems and so they are not usually employed in municipal installations although they have been used in same countries as pretreatment ponds in order to reduce the total hand area required.Their main use in the treatment of coneentrated industrial wastes in isolated places eqquents from anaerobic system require .aerobic teatment before they are discharged to surface waters.

OXIDATION PONDS (facultative ponds):

Most freuently encoontered type much of the volume of these ponds can be either or anaerobic at various times so that growth of facultative organisums which are able to adopt to either condtioned is favoured

High rate aerobic ponds:

influent waste organic matter is broken down arj bacteria the resulting c02 are used by algae to synthesite new algal cells by synthesis.

Deign Of waste stabalization ponds:

ponds systems have traditionally been designed on the basis of

1. Avg.liquid detention time ( t=v/q

0

2. areal organic loading i.e organic loading per unit suface area of ponds (g BOD5/m2 - d

0 or both

table 14 - 4

***Where insufficient attention has been paid to the loading rate on the first pond in a system comprising several axidation ponds in series, severe o dor problems can occur if that pond becames anaerobic hence the design of such systems purely on the basis of average aerial BoD5 Loading Or Total detention time is avedeguate the first pond must not be overloaded

Kinetic -based methood of oxidation pond design: le/4 = 1/ 1 + kt

Thus the minimum value of do is domin = do sat - doc=9.2-7.3 = 1.9mgk

(which is too low to support even coarse fish life and would be considered seriosly polluting)

METHODS OF ANAEROBIC BIOLOGICAL TREATMENTS:

These are suspended growth irroceises and are used mainty for treating the organic sludges removed from wawastewaker in (primery jedimentation and in final sedimentation following aerobic biological treatment.

Anearobic ponds and septic tanks are however used for treating wastewater (rather than sludge).

1. Anaerobic pond
2. Septic tanks
3. Imhuff tanks
4. Anaerobic biological treatment.

Anaerobic Ponds:

Anaerobic ponds are heavily loaded open ponds usually 2 to 4cm deep as permenent ponds in munecypal wate wate treatment or in industrial wastewater treatment. In either case they reduce the organic load applied to a series of facultative or aearobic ponds which are invariably required to futher.

Septic Tanks :

1. Septic tanks are story tanks used for treating wastewater from single households or institutions in area where piped sewage is not available.
2. Operate essentially as combined sedinentation and anaerobic digesion tanks.
3. Well designed tanks should provide a chamber in which reasonasly quiescent settling is allowed to occur.
4. Solids settle to the bottom of the chamber forming a shdge layer while floats and floatables rise to the suface to form a seum layer which helps to prevent occess of oxygen through the liquid surface and aslo helps to control essape of adowrn.
5. These three zones are characteristics of well operated septic tanks
6. In common with effluent from other anaerobic inrocesses septic tanks effluent requires further treatment before the most commonly adspted method for on site disposal.