GB2178735A

GB2178735A - Activated sludge process

Info

Publication number: GB2178735A
Application number: GB08613766A
Authority: GB
Inventors: Yasushi Oda
Original assignee: Ajinomoto Co Inc
Current assignee: Ajinomoto Co Inc
Priority date: 1985-07-01
Filing date: 1986-06-06
Publication date: 1987-02-18
Also published as: PH22690A; MY102967A; JPH0659476B2; GB8613766D0; JPS624497A

Abstract

A process for treating sewage or industrial waste water by an activated sludge process is improved in that biotin or a derivative or precursor thereof is added to the sewage or industrial waste water so as to activate and stabilize the microorganism phase of the activated sludge.

Description

SPECIFICATION Activated sludge process The present invention relates to an activated sludge process for treating sewage or industrial waste water.

According to the present invention, there is provided a process for treating sewage or industrial waste water by an activated sludge process, wherein biotin or a derivative or precursor thereof is added to the sewage or industrial waste water so as to activate and stabilize the microorganism phase of the activated sludge.

The characteristic feature of the present invention lies in directly adding, to the sewage or industrial waste water, biotin (which is known to be a physiologically active substance of microorganisms) or a derivative or precursor thereof, for improving and stabilizing the treating ability of the activated sludge process thereby to maintain or restore the microorganism phase of the activated sludge to a state preferred for removing BOD (i.e. biological oxygen demand) and COD (i.e. chemical oxygen demand) in the raw sewage or industrial waste water.

In order to maintain the rates of BOD or COD removal and the floc-forming ability of sludge, which features are generally referred to as the efficiency of the activated sludge process, it is necessary that bacilli such as Zoogloea ramigera, etc., moulds such as Spaerotilus natans, etc., and other protozoa live in the sludge in a well balanced state. For this purpose, the activated sludge process is controlled by the pH, by the concentration of dissolved oxygen, by the BOD, by the COD load, by the amount of mixed liquor suspended solids (MLSS) in an air-exposed tank, etc. However, the process is liable to be readily affected by various external factors such as a change in the natural environment (e.g. atmospheric temperature, etc.), a quantitative or qualitative change in the raw sewage, etc. These factors are the main ones that control the activated sludge process.Once the balance of the microorganism phase is lost, a reduction in the BOD and COD removal, or bulking of the sludge, occurs. In serious cases, the operation sometimes comes to a halt.

As a result of extensive investigations, the present inventors have found a simple and economic process for improving the activated sludge process by directly adding to the activated sludge biotin or a derivative or precursor thereof in a trace amount to activate the microorganism phase. The process is also extremely useful for improving the ability of the activated sludge to remove BOD and COD and the floc-forming ability of the activated sludge, by the activation of the microorganism phase in the activated sludge, and for restoring an activated sludge phase in the activated sludge, and for restoring an activated sludge in which the balance of the microorganism phase has been completely destroyed to cause filamentous bulking (i.e. bulking caused by filamentous fungi or microbes) and to cause the ability of the activated sludge to be seriously reduced for a short period of time.

The derivatives and precursors of biotin used in the present invention include, for example, desthiobiotin and compounds of the pelargonic acid group (which compounds include pelargonic acid; 8-ketopelargonic acid; 7,8-diketopelargonic acid; 7-keto-8-aminopelargonic acid; and 7,8diaminopelargonic acid). These compounds are precursors for desthiobiotin which in turn is a precursor for biotin. The biotin or the derivatives or precursors theeof need not be pure but may be used, for example, in the form of cane molasses containing the biotin or derivative or precursor thereof.

With respect to the time at which the biotin or derivative or precursor thereof is added, the activated sludge process is effectively restored for a short period of time by post addition when the balance of the microorganism phase has been lost and filamentous bulking, etc., has occurred to cause a reduction in the operation of the activated sludge process. When a reduction in the operation of the activated sludge process is expected, the addition may also be performed previously, at the initial stage of the activated sludge process to prevent such a reduction in the operation. Furthermore, even when no reduction in the operation is noted, the addition at the initial stage can cause the activated sludge process to proceed in an improved way, as compared to the case where no addition is made.

It is sufficient for the biotin or the derivative or precursor thereof to be added in an amount of 0.5 to 100 ppb (parts per billion, wherein "billion" means 109) based on the inflow into an airexposed tank of the activated sludge. With less than 0.5 ppb, the operation fo the activated sludge process is not usually improved or restored. Furthermore, with greater than 100 ppb, the degree of improvement or restoration of the activated sludge process is substantially the same and therefore the use of an amount exceeding 100 ppb serves no purpose. The optimum amount within the above range can be easily determine by performing a preliminary experiment on a small scale.

The present invention will now be illustrated by the following Examples.

Example 1 In an activated sludge process for the treatment of waste water derived from the purification of a glutamic acid fermentation solution, biotin was continuously added to the activated sludge over a period of 10 days to attain a concentration of 10 ppb. As a result, the growth of the flocs was accelerated and the BOD removal rate and sludge volume (SV) were improved, as is shown in Table 1.

The conditions for the operation of the activated sludge process were as follows: Volume of air- 30 litres (laboratory exposed tank scale device) Concentration of dissolved oxygen 1.0 ppm Concentration of BOD in the inflow water 2000-2200 ppm Water temperature of the activated sludge 25-30 C phi 6.5-7.0.

For the purpose of comparison, the procedure was repeated except that no biotin was added.

The results shown in Table 2 were obtained.

Example 2 In an activated sludge process for the treatment of waste water derived from the purification of a glutamic acid fermentation solution, filamentous bulking occurred to a serious degree. For restoration, the present process, as described hereinbelow with reference to Table 3, was used.

As can be seen from Table 3, the process operated normally during the initial period of 1 to 7 days. During the next period of 8 to 17 days, filamentous bulking occurred to cause a reduction in efficiency such as a marked reduction in the COD removal rate, a reduction of the condensation rate of returned sludge due to a reduction of sludge precipitation, a penetration of sludge into the outflow, and so on. During this period, the activated sludge was predominated almost by moulds and no existence of protozoa could be found. During the next period of 18 to 24 days, biotin was continuous added to the activated sludge tank to attain a concentration of 5 ppb. On the 19th day, two days after the addition, the microorganism phase began to change and bacilli and protozoa appeared.On the 22nd day, 5 days after the addition, the microorganism phase was almost restored, the sludge precipitation was improved and the leakage of sludge into the outflow decreased. On the 25th day and thereafter, the microorganism phase was completely restored and therefore the addition of biotin was discontinued. The efficiency of the activated sludge process was fully restored.

Heretofore, a long period of 1 to 3 months was generally required for the recovery of an activated sludge process in which filamentous bulking had occurred to such a serious degree that bacilli and protozoa had disappeared, even when the COD load is reduced by an extreme amount (1000 to 1500 ppm), or when normally-working activated sludge is added to the sludge.

In the case of the present Example, the restoration can be effected in a short period of time of about 10 days, which maintaining a high COD load (the COD load of the inflow during the addition of biotin was 2.1-2.4 kg/m3.day).

The conditions for the operation of the activated sludge process were as follows: Volume of airexposed tank 2400 m3 Concentration of dissolved oxygen 0.2-1.0 ppm Load of COD in the 3000 ppm (corresponds inflow water to 2.3 kg/m3.day).

Water temperature of the activated sludge 30-35 C pH 6.5-7.0.

Example 3 In a process for the disposal of sewage by the activated sludge process, it was confirmed that the treating efficiency was improved by the addition of desthiobiotin. As can be seen from the results shown in Table 4, an improved BOD removal rate was obviously confirmed in the case where 4 ppb of desthiobiotin was added. In the case of the addition of 40 ppb of desthiobiotin, the treating ability was further improved. The experiment was carried out, on a laboratory scale, using a 30 litre air-exposed activated sludge tank. During the experimental period of 6 weeks, increased counts of microorganisms were observed in the cases where desthiobiotin was added. In these cases the increase of stalked automatic protozoa was characteristic.

Table 1

BOD Removal Days BOD Load Rate MLSS SV30 passed (Kg/m3.day) (%) (ppm) (%) o 1.55 94.5 6050 97 2 1.60 96.0 5950 90 4 1.55 98.0 6100 78 6 1.55 98.5 6250 72 8 1.50 97.5 6050 65 10 1.55 98.0 6150 67 Table 2

BOD Removal Days BOD Load Rate passed 3 MLSS SV30 (Kg/m.day) (%) (ppm) (%) 0 1.55 94.5 6050 97 2 . 1.60 91.0 5600 96 4 1.55 88.0 5350 98 6 1.55 94.0 5900 92 8 1.50 95.0 6000 93 10 1.55 91.5 5550 98 MLSS: mixed liquor suspended solid in air-exposed tank SV30: sludge volume after 30 mins. Table 3

Concentration of MLSS Days Concentration passed of COD Activated Concentration COD Sludge in Rate Removal Air-Exposed Returned of Inflow Outlfow Rate tank Sludge Sludge Outflow (ppm) (ppm) (%) (ppm) (1) (ppm) (2) (2) (1) (ppm) 1-7 3804 280 92.5 5526 9026 1.63 27 8-17 3907 694 79.0 4907 6918 1.41 209 18-24 2928 572 78.3 5306 7079 1.34 82 25-31 3440 315 90.1 6639 8624 1.30 42 32-41 3310 221 92.8 6208 9621 1.55 25 Table 4

BOD (mg/l) Removal Addition Rate Amount of Days Inflow Outflow [%BOD] Desthio passed (average) (average) (average) biotin 1 180 47 70.9 no addition 3 280 124 55.6 5 210 48 77.3 8 150 82 45.2 10 350 175 50.0 14 300(245) 114(98) 62.0(60.2) 16 370 200 46.0 4ppb 19 260 99 62.0 based on 21 160 20 87.7 inflow 23 330 77 76.8 25 290 64 77.8 28 280(282) 52(79) 81.3(71.9) 31 220 51 76.8 40 ppb 33 260 68 86.7 based on 35 290 64 77.8 inflow 37 380 68 82.2 40 220 25 88.6 42 310(280) 56(50) 81.8(82.3)

Claims

1. A process for treating sewage or industrial waste water by an activated sludge process, wherein biotin or a derivative or precursor thereof is added to the sewage or industrial waste water so as to activate and stabilize the microorganism phase of the activated sludge.

2. A process according to claim 1, wherein the biotin or the derivative or precursor thereof is added in an amount of from 0.5 to 100 parts per billion, based on the amount of sewage or industrial waste water.

3. A process according to claim 1, substantially as described in the foregoing Examples.