CS231375B1 - The method of pre-treatment of wastewater from the production of urea-formaldehyde adhesives - Google Patents

Abstract

The purpose of the invention is to eliminate the poorly stable urea-formaldehyde condensate from the effluent from the production of urea-formaldehyde adhesives, thereby eliminating the possibility of clogging of pipelines and treatment facilities. This purpose is achieved by treating the waste water from the production of urea-formaldehyde adhesives with an inorganic or organic acid to a pH of 1-5, preferably to a pH of 1.2-2. The precipitated urea-formaldehyde condensate is separated off, preferably by filtration or sedimentation, and the acidic filtrate or pre-treated wastewater is purified biologically after neutralization.

Description

1,231,375

BACKGROUND OF THE INVENTION The present invention relates to a process for the purification of waste water from the production of urea-formaldehyde adhesives comprising urea-formaldehyde condensate, formaldehyde and urea.

Urea-formaldehyde condensate found in wastewater from urea-formaldehyde adhesives; just stable, falling out of solution and sealing transport trails. Freeformaldehyde is particularly toxic for subsequent biological treatment of waste water.

Wastewater with a higher formaldehyde content is in many cases purified by physico-chemical processes, by catalytic oxidation of hydrogen peroxide in the presence of iron metal, salt of iron, other alkali metal salts, or metal of alkaline minerals, platinum / Japanese patent applications 44 906/72, 111 085 / 81,24 694/82, patent ZS3R 552309, patents NSR 2703267, 2703268 /, oxidation of hypochlorite in the presence of nickel oxide on PVC carrier (Japanese Patent Application 27075/80) ·

Also known are methods for the biological purification of waste water with higher free formaldehyde activated sludge content (U.S. Pat. No. 792214); at a temperature of 40-90 ° C.

It has been found that waste waters contaminated with free formaldehyde can be purified with high efficiency by adapted activated alkaline at concentrations of 200-2,000 mg / m @ -1. Therefore, one of the major problems encountered in the purification of wastewater from production of urea-formaldehyde adhesives is the clogging of traffic routes and cleaning equipment with fallen urea-formaldehyde condensate.

The above mentioned problems eliminate the use of a new waste water purification process ·

BACKGROUND OF THE INVENTION The present invention relates to a process for the purification of waste water from the production of urea-formaldehyde adhesives comprising urea-formaldehyde condensate, formaldehyde and urea. Waste soda ash for the production of urea-formaldehyde adhesives is treated with an inorganic or organic acid, preferably hydrochloric acid, sulfuric acid or formic acid, preferably at pH 1.2-2.

After evaporation of the precipitated urea-formaldehyde condensate, preferably the use of filtration or automatic sedimentation, the safiltrate or pre-treated wastewater is biologically purified. Preferred is the pre-treated acidic water for acidic decomposition of waste waters containing unstable formaldehyde compounds in the acidic environment, for example hexamethylentetramine , dinitrozopentame-tylentetramine · From the point of view of the urea-formaldehyde binder production technology, the main advantage of the method of wastewater pretreatment according to the invention is the elimination of the possibility of clogging of the sewage and sewage treatment plants with urea-formaldehyde condensate. Example 1

State prior to application of the invention. Untreated waste waters from the production of urea-formaldehyde adhesives have the following composition; CODCr = 15 140 mg.l ”1 free formaldehyde = 550 mg.l” 1 nitrogen content = 0.58% evaporator = 16.2 g ·! ”^ PH = 6.4 Partially dropped urea-formaldehyde condensate chamber clogged pipes are transported to the waste water treatment plant 231 375 by tank wagons, which considerably economies in wastewater treatment from the production of urea-formaldehyde adhesives.

Into five beakers containing 600 ml of waste water from the urea-formaldehyde adhesives (above), an amount of sulfuric acid was added to bring the pH of the individual beakers to 1.2 > 1.4 $ 1, 8 and 2.7 $ / 4.25 ml, 2 ml, 0.86 ml, 0.40 ml and 0.17 ml of concentrated sulfuric acid.

The mixture was stirred at ca. min. ”1. Samples taken at half-hour intervals were filtered with S-4- frit. COD, total nitrogen, free formaldehyde and residue were determined in the filtrate. Results are shown in the table. time / min / 30 60 90 120 150 COD /mg.l”1/ pH = 1, 2 6 630 5 240 4 520 4 230 4 200 COD /mg.l"1/ pH = 1, 4 7 520 6 160 5 260 4 720 4 630 COD /mg.l”1/ pH = 1, 6 8 390 7 600 6 200 5 870 5 630 COD /mg.l”1/ pH = 1, 8 10 600 8 720 8 110 7 980 7 540 COD /mg.l”1/ pH »2.7 15 100 15 040 14 900 14 380 13 290 H /% / pH-1.4« «0.20 - 0.15 - 0.13 evaporator / gl 1 (pH = 1.4) 6.7 - 4.3 - 3.6

The free formaldehyde concentration did not change significantly over the individual samples during the experiment. Example 3 231 375

Two volumes of formic acid were also added to two beakers containing 600 ml of waste water from the urea-formaldehyde production to give 1.7 and 2.1 / 30 ml and 3 ml of 80% formic acid in each beaker. /. The mixture boiled at about 50 rpm. min “'” *. At half-hour intervals, the sampled samples were filtered with S-4 frit and COD was determined in the filtrate. The results are shown in Table. time / min / COD /mg.l"1/CHSK /mg.l"1/30 60 90 120 150 pH «l, 7 9 860 8 500 80 050 7 630 7 420 pH« 2, l 12 540 11 060 10,200 9,850 9,300 tf

Claims (1)

Object of the invention 231 375 Waste water pretreatment process for the production of urea-formaldehyde adhesives comprising urea-formaldehyde condensate, formaldehyde and urea, characterized in that the wastewater is treated with an inorganic or organic acid, preferably hydrochloric acid, sulfuric acid, or scavenger acid, to a pH of 1-5, preferably to a pH of 1.2-2, after homogenization of the mixture, the precipitated condensate is separated, preferably by filtration or sedimentation.