I am new to waste water treatment. I own a small herbal extract manufacturing unit. We need to treat 15000 L of botanical aqueous extract every day. I tried the following expt
waste water (light green) > pH adjustment with NaOH to 9-10 > the color became dark brown > added ferric chloride and sludge separated out > filtered > the color of filtrate is still dark brown.
In fact the color of starting waste water was much lighter than the processed water.
I feel there is some pH relationship with color but dont know how to handle. Pl help!

I just passed the effluent through a bed of celite. The solution became clear but surprisingly the color of eluant changed very dark. Maybe the celite caused some change in pH thereby having an influene on the color.  Quite unusual as I always thought celite is very inert. Will check the in and out pH tomorrow.

Ok will check and inform.
Further checked out some more parameters of starting effluent - COD is 28,000 ppm, TDS is 1.5 %, pH of effluent is 5.
Can this effluent be treated only by coagulation / flocculation or biological treatment required after coagulation / floculation.

The objective of wastewater treatment is usually to clean from the wastewater enough solids to let the rest to be released to a getting water without disrupting its best or appropriate use.

If I can process the waste water and bring down the level of COD of say 2500 ppm, will it be safe to use it in my garden? Of course, it would depend on what is the type of chemical which is being reflected in the  COD, but considering that all these chemicals have come from natural source (primarily herbs), will 2500 ppm be ok? I am sure that when we add fertilizers in the garden, the COD would be quite high but these are all because of nutrients which are good for the plants. Is there some way to find whether the 2500 ppm water has nutrients which would promote the growth of plants?

You need to analyse the effluent for pH, Chemical Oxygen Demand, Biochemical Oxygen Demand, Nitrogen & Phosphorous, then establish the nutrient requirements for the crop growing on the land where the effluent is to be applied, so that you can calculate an acceptable application rate.
This is not a "landfilling" operation, it is a nutrient recovery process, with benefits also being achieved from the water.  
If the plants have withered there is something wrong with the effluent or with the application rates.
If the effluent is biodegradable and non-hazardous, and if the pH is not too high or too low, and if the nutrient addition rates are properly calculated I would expect the plants to flourish, not to wither.

I would check the discharge for the common nutrients such as P and N before concluding that the COD is composed of these nutrients. Usually, the PO₄, NH₃ and NO₃ nutrients will not affect COD. TOC analyses may also be informative.

grrun

Suppose there is chlorophyll content in my waste water is high, it should be good for the garden, but this would translate into a high TOC. How should I interpret this?

This is an aqueous botanical herbal extract process. This I understand to mean that water is being used to extract water soluble materials from plants/herbs.
I believe therefore that it is most unlikely that water from this process will be hazardous.
Application of water containing high TOC or high COD would NOT be expected to cause plants to wither. However if the plants are
overwateted, or if excessive nutrients, (particularly Nitrogen), is applied, then withering may occur.
Of course if the water contains some hazardous materials, or is at an unusually high, or unusually high, pH, then withering may also occur.
The practice of land application of huh strength waste waters or flurries is common throughout the world, and is regularly used on farms, and at many food processing plants, (like this case).
So in this case you need to establish that the pH of thi water is acceptable, that the water is not hazardous, or does not contain any hazardous substances, then measure nitrogen & phosphorous content of the water. Review the results, prepare a suitable Nutrient Management Plan, which will guide you through the correct application rates.

Thanks all. I think it may be difficult to actually monitor / control direct land application as the person usually doing such works would be unskilled and I have a beautiful garden which I cannot risk. Tell me if this alternative sounds good - I treat the water to reduce sludge and the COD is brought down to say 3000 - 3500 ppm but is slightly coloured. The limit for discharge is 250 ppm COD but I keep a higher limit since the water prima facie should have nutrients. In the mean time, I get the water analysed for BOD, TOC, N, P which would help us understand the long term application problems.

Hi Navin,
Firstly it is not difficult to control land application of "organic" wastes such as you have. Once you know the make up of the water, the crop growing in the land onto which the water is to be applied, and the phosphorous content of the soil on the lands, it is relatively easy.
I would be pleased to help you if you could send me the information.

Secondly it seems a shame that you start adding chemicals to a water that currently appears only to contain organic substances. If you do not wish to use the soil as a biological treatment plant, (while also recovering valuable nutrients), then you should consider a convention biological treatment plant not requiring chemical addition.

Where is the discharge currently going?

Hi Tom, just to add, it's been about 2 weeks that we started this product, so I am not sure about the long term effect of this spraying.

I have about 4000 sq m barren space and about 4000 sq m garden area.
Waste water generation is 6 days / week @ 15000 L / day and about 6 months in a year.

Tom is right ..
Tom Keenan - nesa wrote on May 18^th, 2012, 4:40am:


Why use any chemicals such as alum .. just adjust the pH for your plants.  You would be adding 1.9 L per sq meter.  I don't think that is a lot of liquid.  what would buildup is the nutrients in the soil.  You may need a heavy nutrient uptake plant like corn.   You also may need to increase the size of available land just to avoid nutrient buildup.  Also I would not spray on the plants .. A subsurface injection would be better.

Do it right like Tom has indicated and when you garden does well, try and sell the extra liquid to you neighbors.

It will be sometime next week .. have to ask agricultural extension service people.  Sat and Sunday is their day off.

Not sure why you worry about the color .. Soil bacteria are color blind.  Just concerned about the low pH for vegetables and root crops.

Also can you give the general range of air temperature during the 6 months.