LETTERS Milorganite lives on
like the SaS series of W
free filter papers “Ribbon” means only one thing t o a chemist. It means the S&S trademark for its series of highest grade filter papers for use in quantitative analysis. S&S grades are identified by color on the box. Scientists who use these analytical working tools claim they are the highest quality, best performing, lowest ash quantitative filter papers on the market. Select from these premium Ribbon grades.
RIBBON
RIBBON
Rapid, Soft. Loose texture. For coarse and gelatinous w t s .
Extra thick. Provides increased retention without loss of filter speed.
RIBBON
RIBBON
Medium speed and retention. Quantitative gravimetric analysis.
Dense. Highly retentive. Filtrat,ion of crystalline materials.
No. 589 RIBBON
SaS 589 Ribbon Series Ash-Free Filter Papers-world’s finest, but no price premium
High wet-strength. For very fine precipitates.
r-------’
1 1
COUPON FOR SAMPLER
SCHLEICHER & SCHUELL CO., KEENE,N.H.
Please send the analytical filter, paper sampler which includes black, white and blue high grade analytical filter papers; plus Conversion Table. NAME:
I I I
CITY:
STATE:
I I
I I I I
ADDRESS:
----------_---.
I
ZIP:
ES-BSB
Circle NO. 11 on Readers’ Service Card
574 Environmental Science and Technology
I
J
DEARSIR: The comments by Dr. Abel Wolman about Milorganite in a recent issue of ES&T (April 1968, page 254) may have created some confusion about the product and its measure of success, Therefore, we wish to call your attention to the following: 1. Milorganite has been produced and sold since 1926-not the “fifties” as stated in the article. 2. We have no intention of discontinuing production at our Jones Island Plant. The decision to start a primary treatment plant on the South Side relates to the nature of the sewage it will receive. It will be primarily urban wastes of low fertilizer value. 3. We continue to sell everything we produce, and, at a substantial savings to our taxpayers. In calendar 1967, we sold 94,005 tons. It is shipped to every state in the Union, Canada, and other foreign countries as well. 4. Although not “money making” in the sense that industry would look at the picture as based on production costs, the sale of Milorganite has paid for the original capital investment and continues to pay for much of the plant operation. It has been estimated that to dispose of our solids by any other known method would cost the taxpayers in excess of $2,000,000.00 per year. This is due to the tremendous load of solids contributed by our breweries and packing house industry. It is industry’s contributions that also give Milorganite the highest nitrogen analysis of any known activated sewage sludge. 5. By inference to San Diego’s problems, the article implies that any activated sewage sludge isn’t “really good fertilizer.” Nothing could be farther from the truth with our Milorganite. Florida and Georgia report less nematode injury on turf grass plots where Milorganite has been compared with other nitrogen sources. New Jersey, Iowa, and Rhode Island have found less turf grass diseases in similar nitrogen studies. Wisconsin
proved many years ago that Milorganite was an excellent source of available secondary and minor nutrient elements. All of this is in addition to its superior nitrogen release and nonburning qualities.
Charles G . Wilson Head Agronomist Turf Service Bureau Sewerage Commission of the City of Milwaukee, Wis. Phosphate removal costs are low
DEARSIR: I would like to point out a few considerations overlooked by W. D. Hatfield in his letter appearing in your June issue. Dr. Hatfield expresses concern about the extra sludge handling costs which might be anticipated when the Dow Process is applied for phosphate removal. We certainly do expect to remove more dry sludge solids when we remove phosphate as precipitated mineral matter; however, we also expect reduced volumes of wet sludge to be sent to the digester. All of the pertinent data that Dow has collected indicate that the treatment of raw wastes with combinations of metals and polymeric flocculants results in the production of additional primary sludge. The same data show that there is also a concurrent reduction in the quantity of excess secondary sludge. Primary sludges are ordinarily put into the digester at solids concentrations of about 5 % . Excess secondary sludge carries much more water, and, regardless of the route it takes to the digester, it puts more water into the digester. One to one-and-a-half per cent solids concentration for settled, activated sludge is a good figure. T o cite an example: Moving the sludge load forward in the plant at Grand Rapids, Michigan. resulted in a reduction in the total volume of sludge sent to the digester. This, in turn, increased digester detention time to 32 days from 19 days. yielded a more
