Special Reprint

Moisture Analysis in Sewage Treatment Plants

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Sartorius AG, Weighing Technology

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Moisture Analysis in Sewage Treatment Plants. The New MA30 Moisture Analyzer from Sartorius.
Sartorius AG in Goettingen, Germany, has developed a new quick moisture analyzer for determining the moisture content or dry weight of liquids or solids. 1. Introduction Determination of the moisture content and % solids in sewage water is a daily task at sewage treatment plants. This type of analysis provides important information about the sludge concentration in activated sludge tanks which is very important for the biological degradation of organic substances by microorganisms and the optimal cleaning capability associated with it. This information is also essential for the removal of tank sludge from the fermenting tower. In fact, the residual moisture content in sludge is also a determining factor for subsequent treatment. Sludge must be dewatered before it can be transported to a waste dump or to an incinerator. A high water content leads to higher transportation costs, which can quickly become a significant cost factor if large amounts of sludge are being transported. In addition, waste dump or incinerator operators define a minimum amount of dry weight which can be present in sludge delivered to the site of disposal. If they did not define a minimum amount, they could not store or burn the sludge economically. The moisture content is also an important measure for calculating the maximum amount of treated sewage sludge permitted to be used for land application in agricultural production areas. 2. Equipment Description The Moisture Analyzer 30 (MA 30 for short) is a quick moisture analyzer featuring a built-in, 1-mg resolution weighing system with a 30-g weighing capacity and an infrared heat source which can reach temperatures ranging between 60 and 160C (settings adjustable in increments of 5). Like a drying oven used with an

external balance, the MA 30 functions on the basis of thermogravimetric analysis. However, the MA 30s special performance feature is its ability to dry a sample extremely quickly (usually in 5 to 15 minutes) and automatically calculate the moisture content or dry weight in percent. Moisture analysis is completely automatic and ends as soon as the resulting weight of the sample remains constant. There is no need to weigh the sample dish before the drying procedure or backweigh the sample after drying because the MA 30 takes care of these tasks during the analytical procedure. Liquid and pasty samples are typically applied to a glass fiber filter to ensure equal distribution of the sample and

accelerate the drying process. The drying parameters can be set by following the symbols displayed in the user menu for guidance. All selected operating parameters are stored in the non-volatile memory. 3. Substance Analysis The following instructions are based on DIN 38409, Part 1, Determination of total dry residue, fiItrate dry residue and residue on ignition (H 1) and DIN 38409, Part 2, Determination of filterable matter and the residue on ignition (H 2).

Special Reprint

3.1 How to Determine the Total Dry Residue Press the <ENTER> key to tare the 1-mg weighing system built into the MA 30. Place an aluminum sample dish (with a glass fiber filter on top) on the cross-shaped dish retainer of the MA 30. Lower the hood to start drying. This procedure dries the sample dish and the filter prior to actual moisture determination; it ends automatically. Using a scoop with a sufficient capacity, remove a sample from the tank. Retare the MA 30 with a dry sample dish and filter in place. Place the sample on the filter and start the drying routine by lowering the hood. You can toggle the readout on the MA 30 among % moisture, % dry weight, and actual weight. You can also have the result output on hard copy by an on-line printer. Convert the result into mg/l. 3.2 How to Determine the Filtrate Dry Residue Run this drying routine as described in section 3.1 with one exception: place the glass fiber filter in a porcelain strainer after the first drying procedure, and filter the sample (sewage water) through it (according to DIN 38409, Parts 2 and 3, Parameters characterizing effects and substances (group H); determination of filterable matter and the residue on ignition). This is based on the DIN H2-3 standard procedure listed under 5.3.3 for quantitative determination of filterable substances, which can be removed with a glass fiber filter, and of the residue on ignition. Afterwards, place the filter back on the sample dish and start the moisture analysis routine as described. At the end of the routine, convert the result again into mg/l. 3.3 How to Determine the Ash Content If you need to determine the ash content after drying a sludge sample, please take the following into account prior to drying the sample as described in sections 3.1 and 3.2:

Pretreat the glass fiber filter according to DIN 38409, Part 2. Determine the filter weight after the incineration procedure. Afterwards, using the pretreated glass fiber filter, you can determine the filtrate dry residue and the ash content using the MA 30 and a muffle furnace. 3.4 How to Determine the Water Content and Dry Residue of Sludge Dry an aluminum sample dish along with a glass fiber filter in the MA 30 as described in section 3.1. After taring the MA 30 with the sample dish and filter in place, place the sludge sample (e.g., centrifuged or stored sludge) on the sample dish. Dry the sample at 105C in the MA 30 fully automatic mode until the weight readout remains constant. Make sure to evenly distribute the sample on the glass fiber filter. Furthermore, be sure that uniform heating of the sample is ensured (e.g., do not place too much of the sample on the sample dish because it could develop a crust and, consequently, inhibit evaporation of the moisture). 3.5 How to Determine the Dry Weight of Activated Sludge Remove a premeasured volume of sludge from the tank and filter it through the dried glass fiber filter. Please follow the directions in section 3.1 to complete the rest of the procedure. This moisture determination routine analyzes the original sample from the activated sludge tank. Remove only the volume of sludge required for analysis (e.g., 250 ml). Filter off the liquid (use a small amount of water in a spray bottle to flush out any remaining sludge from the scoop), and dry the filter cake. You can have the result displayed either as a percentage of the dry weight or as the actual weight on the MA 30. In the weight display mode, the result must be extrapolated to one liter (result in g/l) according to the volume of sludge analyzed.

If you analyze a sample taken directly from the tank, it is not necessary to homogenize the sample by stirring it. Homogenization is usually necessary if a sample of activated sludge has been taken previously with a largevolume container. If the activated sludge is allowed to stand in a container, such as a bucket, sedimentation of heavy particles can occur, causing the sample to separate. You must alleviate this condition by stirring the substance. In summary, the MA 30 simplifies and accelerates moisture analysis and dry weight determination when used for the same operations as a drying oven connected to an external balance. If you are planning to buy new equipment, or if you wish to use a faster and equally accurate method of analysis, the MA 30 offers you an alternative to methods used in the past. The operating instructions are written with reference to DIN 38409, Parts 1 and 2, and DIN 38414. The quotes are taken from the same sources. Example of a Moisture Analysis Printout: 23-JUL-90 07:43:17 A 0.0 min 105 C 5.327 g 3.0 23.22 L 6.0 44.15 L 6.3 min 44.21 L 23-JUL-90 07:43:17 = date and time A = fully automatic operating mode 0.0 min = length of drying routine has not been defined 105 C = selected operating temperature in Celsius 5.327 g = initial weight of the sample (prior to drying) 3.0/6.0 = 3-minute cycle set for printouts of the intermediate results 23.22/44.15 = moisture content determined so far L = (L)ost: selected display mode in % moisture 6.3 min 44.21 L = total drying time and final result

Technical Specifications

Overview of Performance Features and Specifications Weighing system accuracy (mg) Repeatability, average (%) for approx. 1 g initial sample weight for approx. 5 g initial sample weight Readability (%) Automatic conversion of the weight difference in % moisture, % dry weight or % weight ratio Max. weighing capacity (g) Selectable operating modes fully automatic timer mode 0.1...99 min. Non-volatile memory for drying programs/sample-specific parameter settings Heat source IR dark radiators (tubular heating elements) Heat regulation and settings temperature regulation from 40C...160C; can be set in increments of 5 Storage of values final value until next analysis Data interface RS-232 C to transfer data to a printer, recorder or a PC Line voltage (V) Permissible voltage fluctuations (%) Frequency (Hz) Max. power consumption (VA) Housing dimensions (Wx D x H in mm) Approx. weight (kg) Accessories Data printer with date/time functions BalanceReader software for processing weighing data for spreadsheet programs MA 30 weight 10 g (3 weights are needed for calibration) Expendables Disposable aluminum sample dishes,90 mm diameter, box of 80 )
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MA 30 1 0.2 0.05 0.01 q 30 q q 1 q q q q 115/230 +10/15 4860 400 217x 283 x165 5.5 Order no. YDP 03-0CE YAK 10 PC-0002 6704-04 Order no. 6965542 6906940 6906920 6906918 YDB 02 MA

Glass fiber filters for quick analysis of liquid, pasty or oily substances, 90 mm diameter, box of 80 Standard-sized paper rolls for printer, 14 m in length, box of 5 rolls Ink ribbon for printer, 1 per package Carrying case q = standard ) = included with each MA 30
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Large paper rolls (for the YDP 03-0CE Data Printer only), approx. 50 m in length, box of 5 rolls 6906937

Sartorius AG, b 37070 Goettingen, Germany p Weender Landstrasse 94 108, 37075 Goettingen, Germany t (+49/551) 308-0, f (+49/551) 308-3289, www.sartorius.com

Specifications subject to change without notice. Printed in Germany on paper bleached without any use of chlorine W/sart-023 G Publication No.: W- -8009-e99063