CN103387288A - Improved UCT sewage treatment plant - Google Patents

Abstract

The invention discloses an improved UCT sewage treatment plant, in which sludge is returned back to not an anoxic zone in a tranditional UCT sewage treatment plant but an aerobic zone, therefore bad influence to nitrogen and phosphorus removal in anoxic zone of a UCT reactor because of large volume of dissolved oxygen and nitrate nitrogen in backflow sludge is avoided. The improved UCT plant has good effect to municipal sewage processing.

Description

An improved UCT sewage treatment device

technical field

The invention belongs to the technical field of environmental engineering, in particular to a novel and improved UCT sewage treatment device.

Background technique

People pay more and more attention to the environment, which leads to continuous improvement of sewage discharge standards, and these sewage discharge standards are protected by law and supervised by public opinion. In my country, nitrogen and phosphorus pollutants are one of the most important pollutants, and their discharge has been strictly supervised and restricted. Theoretically, the A2/O process has a good pollutant removal effect, and has good sludge settling performance and low energy consumption. The A2/O process can remove a large amount of nitrogen pollutants through nitrification and denitrification process, and through the process of alternating anaerobic aerobic and anoxic processes, phosphorus accumulating bacteria can absorb and release phosphorus excessively to remove phosphorus pollutants. However, the disadvantage of the A2/O process is that the nitrate nitrogen in the return sludge enters the anaerobic tank, destroying the anaerobic state of the anaerobic tank and affecting the removal rate of phosphorus pollutants in the system. So in response to the above problems, people developed the UCT process. The UCT process is a sewage treatment process that is widely used in my country. It has been favored by many domestic sewage treatment plants for its high cost performance and relatively stable treatment effect. However, the treatment effect of the existing UCT process still has many areas worth improving. The reason is that there are a large amount of dissolved oxygen and nitrate nitrogen in the return sludge, and they will all flow back to the anoxic zone of the UCT reactor to affect the anoxic process. area response. The removal of phosphorus pollutants was also affected because the return sludge contains a large amount of nitrate nitrogen nutrients, which can promote the growth of non-phosphorus accumulating bacteria in the anoxic zone.

Contents of the invention

The purpose of the present invention is to provide an improved UCT sewage treatment device, which can avoid the existing UCT from causing adverse effects on the denitrification and phosphorus removal in the anoxic zone due to the presence of a large amount of dissolved oxygen and nitrate nitrogen in the return sludge .

The technical scheme of the present invention is: a kind of improved UCT sewage treatment device, comprises anaerobic reactor, anoxic reactor, aerobic reactor, clarifier, anaerobic reactor connected with anoxic Internal return pipes are provided between the reactors, and between the anoxic reactor and the aerobic reactor, and the feature is that the return sludge after passing through the clarification tank is connected with the aerobic reactor.

Beneficial effects: a large amount of dissolved oxygen in the return sludge of the present invention enters the aerobic zone, which can promote the degradation of COD by microorganisms in the aerobic zone, and at the same time, a large amount of nitrate nitrogen in the return sludge enters the aerobic zone, which can Promote the denitrification effect of microorganisms in the aerobic zone to a certain extent. The invention has good treatment effect on municipal sewage.

Description of drawings

Fig. 1: Schematic diagram of the structure of the device of the present invention;

Figure 2: The relationship between hydraulic retention time and pollutant removal rate, where a: COD and TP, b: TN, NH4+-N and KN;

Figure 3: The relationship between hydraulic retention time and specific removal rate of pollutants, where a: COD and TP, b: TN, NH4+-N and KN.

Detailed ways

The present invention is described in detail below by embodiment:

Example

Fig. 1 is the improved UCT process used in the present invention. During the improved UCT treatment, the returned sludge enters the aerobic zone, thereby avoiding the influence of dissolved oxygen (DO) on the anoxic and anaerobic zones. The total volume of the device used for the pilot test is 128L, with an anaerobic reactor of 10L, anoxic reactor of 26L, aerobic reactor of 90L, and a clarifier of 2L (Fig. 1).

(1) The properties of inflowing municipal sewage are shown in Table 1. During the whole experiment period, the indicators of influent, effluent and sludge were tested every 4 days, with a total of 36 sets of data. All pollutant tests are conducted in accordance with the standards of the American Public Health Association (APHA). Suspended solids (SS) and dissolved oxygen (DO) were measured using Surface Scatter7sc device (HACH, USA) and Z LLIGS-14device (HACH, USA), respectively. pH and temperature were measured using HACH GLIPH/ORP device (HACH, USA). The pH and DO of domestic sewage were measured daily, with typical pH values ranging from 6.0 to 7.6 and DO consistently above 1 mg L-1 (Table 1).

Table 1: UCT influent properties (mg L-1)

(2) As shown in Figure 2a, UCT can maintain a high COD removal rate, which can reach up to 96% when the hydraulic retention time is 15h (the third stage, 81-120 days, 21-30 sets of data), but compared with The degradation rate showed a trend of increasing first and then decreasing, and its maximum value reached 8.80×10-3h-1 at the hydraulic retention time of 15h (Fig. 3a). In the process of activated sludge process, COD removal rate and hydraulic retention time are always proportional, but in this experiment, the highest COD removal rate did not appear in the maximum hydraulic retention time of 24h. The reason may be that under longer hydraulic retention time conditions (such as 19h or 24h), the flow rate of water flow in anaerobic, aerobic, anoxic and clarifier tanks, and aerobic to anoxic and anoxic The internal reflux rate to anaerobic, and the sludge reflux from clarifier to anoxic will be slowed down and reduced to varying degrees, so that the number of aerobic bacteria in the aerobic area may be less, thus affecting the degradation of COD pollution .

(3) The removal rate of total phosphorus (TP) in Figure 2a first increased and then decreased, and the removal rate reached a maximum of 85% at 19 hours (the second stage, 41-80 days, 11-20 group data). The specific removal rate of TP remained at a low level throughout the experiment, with little change, and reached a maximum value of 2.90×10-3h-1 at a hydraulic retention time of 19h (Fig. 3a). The average removal rate of TP in the first stage was only 54%, but it rose to 79% and 72% in the second and third stages, and suddenly dropped to 49% in the fourth stage. This shows that the optimal hydraulic retention time is between 19 and 15 hours, which coincides with the generation time of PAO. Therefore, 19h was determined as the optimal hydraulic retention time for TP removal.

In Fig. 2b, the removal rates of total nitrogen (TN), ammonia nitrogen (NH4+-N) and Kjeldahl nitrogen (KN) are proportional to the hydraulic retention time and pollutant removal rate. When the hydraulic retention time was 24h (first stage, 140 days, data set 1-10), TN, NH4+-N and KN reached the maximum removal rates of 72%, 76% and 78%, respectively. Their specific removal rates are consistent with the variation trends of pollutant removal rates (Fig. 2b and Fig. 3b), and reach the maximum values of 1.70×10-3, 1.85×10-3 and 2.05×10 respectively at the hydraulic retention time of 24h -3h-1.

In summary, the removal rates of TN, NH4+-N and KN in the first and second stages are always greater than those in the fourth stage, so the results of this study show that when the hydraulic retention time is long, the UCT unit is more effective for nitrogen-containing Pollutants have a high removal rate.

(4) The improved UCT process of the present invention has achieved a good effect on the purification of urban domestic sewage, but it still needs to be improved in terms of sludge flocculation and sedimentation performance and removal of NH4+-N and COD. The optimal hydraulic retention time is 19h, and the removal rates of COD, TP, TN, NH4+-N and KN can reach 96%, 85%, 72%, 76% and 78% respectively.

Claims (2)

1. improved UCT waste disposal plant, comprise anaerobic reactor, anoxic reacter, aerobic reactor, the settling pond that is connected successively by the sewage disposal order, between anaerobic reactor and anoxic reacter, and be respectively equipped with the internal reflux pipe between anoxic reacter and aerobic reactor, it is characterized in that: the returned sluge after settling pond is communicated with aerobic reactor.

2. improved UCT waste disposal plant as claimed in claim 1, it is characterized in that: the cubic capacity of device is 128L, wherein said anaerobic reactor volume 10L, anoxic reacter volume 26L, aerobic reactor volume 90L, settling pond volume 2L.

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