AIA Current News
Add the AIA newsfeed to Google Reader
january 01, 2008 11:45pm
Wastewater Daily Discussion -
Expert 'Tip & Tricks' from out friends at all-about-wastewater-treatment.com
Today feed is about Toxicity factors that affect pond performance
.JPG)
**Toxic materials**
Stabilization ponds are generally immune to toxic substances and heavy metals. Long detention time allows gradual absorption of the inhibiting substances by the existing biomass, provided there is no shock load. Concentration of 6 mg/l of each of heavy metals like cadmium, chromium, copper, nickel, zinc has not affected the treatment efficiency in a facultative ponds
**Oxygen**
Dissolved oxygen (DO) helps to identify the efficiency of operation in a facultative or maturation pond. A normally functioning facultative pond will be supersaturated with free oxygen at the surface and in the sub - surface layers during the afternoon.
However, DO concentration may reduce to below 1.0 mg/l or even zero at dawn. The aerobic (the one that absorbs oxygen) surface layer strips off odor release in wellmaintained ponds.
**Heavy metals**
Heavy metals do not cause a problem with domestic wastewater since ponds can withstand upto 30 mg/l of heavy metal without any reduction in treatment efficiency.
**Algae and bacteria**
The performance of a pond system directly depends on its constituent algae and bacterial population. Presence of any toxic substance that affects their metabolism will reduce their performance. The algae are more easily affected than the bacteria.
In ponds treating domestic wastewater, the major toxicants are ammonia and sulfide.
**Effect of ammonia**
If ammonia concentration exceeds 28 mg/l, algae may manage if ponds are within pH range during daylight hours. Ammonia is exponentially more toxic above pH 8, since a larger proportion is then in the unionized state, so can rapidly penetrate the algae cell and inhibit photosynthesis. This can cause the facultative pond to behave like an anaerobic one, even when the BOD surface loading is low. However, this can be reversed in a few hours. Inhibition of photosynthesis also reduces pH and hence toxicity of ammonia.
**Effect of sulfide**
Sulfide is toxic to algae in its H(subscript)2S stage. Its toxicity increases when pH decreases. In the normal range of pH in ponds, when sulfide concentration exceeds 8 µg/l, the activities of anaerobic heterotrophic bacteria are inhibited. Concentration of 50
- 150 mg/l inhibits methanogenesis in anaerobic ponds.
Before I sign off today Bob, I'd like to ask you to take a closer look at the All About Wastewater Treatment (Institutional/ Corporate Edition) eBook whose contents has been described at
AllAboutWastewater.com
This is the book with literally hundreds of 'word of mouth' tips and methods- secrets which are next to impossible to find in books
- the gold which only comes from years and years of hands on experience ... including all the hard to find Wastewater Treatment tips and information that people just can't locate with internet searches or trips to the library. For your Institution, this book will be of interest as it would provide you with information as to where to buy the equipment and which theory to follow for the treatment of wastewater at the best price. Detailed information on the different treatment methods as well as basic theories employed for the treatment are also given in the book. This book also gives an insight on How To Run the Wastewater Treatment Plant Effectively and Efficiently.
