低溫廢水回收設備：低溫污水生物脫氮工藝

Low temperature wastewater recovery equipment: low-temperature wastewater biological denitrification process

　　氮素在水體中的過度積累造成了水體富營養(yǎng)化現(xiàn)象，嚴重危害生態(tài)系統(tǒng)安全。一般采用生物法進行廢水脫氮。硝化反硝化工藝是應用zui普遍的生物脫氮工藝。最近十幾年，出現(xiàn)了一些新的脫氮工藝。厭氧氨氧化工藝是其中zui有代表性的突破之一。該方法是利用自養(yǎng)型細菌將氨直接氧化為氮氣而實現(xiàn)脫氮的工藝，與傳統(tǒng)的硝化反硝化工藝相比具有耗氧量低、運行費用少和不需要外加碳源等優(yōu)點，是目前已知工藝中最經(jīng)濟的生物脫氮途徑之一。

The excessive accumulation of nitrogen in water bodies has caused eutrophication, seriously endangering ecosystem security. Generally, biological methods are used for wastewater denitrification. Nitrification denitrification process is a widely used biological denitrification process. In the past decade, some new denitrification processes have emerged. Anaerobic ammonia oxidation process is one of the representative breakthroughs in this field. This method is a process that utilizes autotrophic bacteria to directly oxidize ammonia to nitrogen and achieve denitrification. Compared with traditional nitrification and denitrification processes, it has the advantages of low oxygen consumption, low operating costs, and no need for external carbon sources. It is currently one of the most economical biological denitrification pathways among known processes.

　　生物反應對環(huán)境條件敏感，容易受溫度變化影響。絕大多數(shù)微生物正常生長溫度為20~35℃，低溫會影響微生物細胞內(nèi)酶的活性，在一定溫度范圍內(nèi)，溫度每降低10℃，微生物活性將降低1倍，從而降低了對污水的處理效果。工藝投入運行后，由于四季的交替和所處的地理位置影響，若不加以人工調(diào)控，溫度很難保持適宜。而溫度調(diào)控則會耗費大量的能源。解決這一難題的zuijia途徑就是開發(fā)高效穩(wěn)定的低溫生物處理工藝。

Biological reactions are sensitive to environmental conditions and are easily affected by temperature changes. The normal growth temperature of the vast majority of microorganisms is 20-35 ℃. Low temperature can affect the activity of enzymes in microbial cells. Within a certain temperature range, for every 10 ℃ decrease in temperature, the activity of microorganisms will decrease by twice, thereby reducing the treatment efficiency of wastewater. After the process is put into operation, due to the alternation of four seasons and the influence of geographical location, it is difficult to maintain a suitable temperature without manual control. And temperature control will consume a lot of energy. The key to solving this problem is to develop efficient and stable low-temperature biological treatment processes.

　　近年來國內(nèi)外已有一些研究涉及低溫廢水生物脫氮技術(shù)，提出了一些新方法。筆者將探討低溫對脫氮工藝的影響，比較低溫脫氮工藝的運行策略，并據(jù)此指出低溫脫氮工藝的研發(fā)方向。

In recent years, there have been some studies both domestically and internationally involving low-temperature wastewater biological denitrification technology, and some new methods have been proposed. The author will explore the impact of low temperature on denitrification processes, compare the operating strategies of low-temperature denitrification processes, and based on this, point out the research and development direction of low-temperature denitrification processes.

　　1低溫對脫氮工藝的影響

The influence of low temperature on denitrification process

　　溫度是影響細菌生長和代謝的重要環(huán)境條件。絕大多數(shù)微生物正常生長溫度為20~35℃。溫度主要是通過影響微生物細胞內(nèi)某些酶的活性而影響微生物的生長和代謝速率，進而影響污泥產(chǎn)率、污染物的去除效率和速率;溫度還會影響污染物降解途徑、中間產(chǎn)物的形成以及各種物質(zhì)在溶液中的溶解度，以及有可能影響到產(chǎn)氣量和成分等。低溫減弱了微生物體內(nèi)細胞質(zhì)的流動性，進而影響了物質(zhì)傳輸?shù)却x過程，并且普遍認為低溫將會導致活性污泥的吸附性能和沉降性能下降，以及使微生物群落發(fā)生變化。低溫對微生物活性的抑制，不同于高溫帶來的毀滅性影響，其抑制作用通常是可恢復的。

Temperature is an important environmental condition that affects bacterial growth and metabolism. The normal growth temperature of the vast majority of microorganisms is 20-35 ℃. Temperature mainly affects the growth and metabolic rate of microorganisms by affecting the activity of certain enzymes within microbial cells, thereby affecting sludge yield, pollutant removal efficiency, and rate; Temperature can also affect the degradation pathways of pollutants, the formation of intermediate products, and the solubility of various substances in solution, as well as potentially affecting gas production and composition. Low temperature weakens the fluidity of cytoplasm within microorganisms, thereby affecting metabolic processes such as material transport. It is widely believed that low temperature will lead to a decrease in the adsorption and settling performance of activated sludge, as well as changes in microbial communities. The inhibition of microbial activity by low temperature is different from the destructive effects caused by high temperature, and its inhibitory effect is usually recoverable.

　　1.1硝化工藝

1.1 Nitrification process

　　生物硝化反應可以在4~45℃的溫度范圍內(nèi)進行。氨氧化細菌(AOB)zuijia生長溫度為25~30℃，亞硝酸氧化細菌(NOB)的zuijia生長溫度為25~30℃。溫度不但影響硝化菌的生長，而且影響硝化菌的活性。有研究表明，硝化細菌zui適宜的生長溫度為25~30℃，當溫度小于15℃時硝化速率明顯下降，硝化細菌的活性也大幅度降低，當溫度低于5℃時，硝化細菌的生命活動幾乎停止。大量的研究表明，硝化作用會受到溫度的嚴重影響，尤其是溫度沖擊的影響更加明顯。由于冬季氣溫較低而未能實現(xiàn)硝化工藝穩(wěn)定運行的案例較為常見。U.Sudarno等考察了溫度變化對硝化作用的影響，結(jié)果表明，溫度從12.5℃升至40℃，氨氧化速率增加，但當溫度下降至6℃時，硝化菌活性很低。

Biological nitrification reaction can be carried out within the temperature range of 4~45 ℃. The growth temperature of ammonia oxidizing bacteria (AOB) is 25-30 ℃, and the growth temperature of nitrite oxidizing bacteria (NOB) is 25-30 ℃. Temperature not only affects the growth of nitrifying bacteria, but also affects their activity. Research has shown that the suitable growth temperature for nitrifying bacteria is 25-30 ℃. When the temperature is less than 15 ℃, the nitrification rate significantly decreases, and the activity of nitrifying bacteria also decreases significantly. When the temperature is below 5 ℃, the life activity of nitrifying bacteria almost stops. Numerous studies have shown that nitrification is severely affected by temperature, especially with temperature shocks having a more pronounced impact. Cases where stable operation of nitrification processes cannot be achieved due to low winter temperatures are common. U. Sudarno et al. investigated the effect of temperature changes on nitrification, and the results showed that when the temperature increased from 12.5 ℃ to 40 ℃, the rate of ammonia oxidation increased. However, when the temperature decreased to 6 ℃, the activity of nitrifying bacteria was very low.

　　隨著脫氮工藝的不斷發(fā)展，人們對硝化工藝提出了更高的要求，希望將硝化作用的反應產(chǎn)物控制在亞硝酸鹽階段，作為反硝化或者厭氧氨氧化的前處理技術(shù)，可以節(jié)約曝氣能耗和添加堿量。通過對兩類硝化細菌(AOB、NOB)的更多認識，出現(xiàn)了短程硝化工藝。該工藝的核心是選擇性地富集AOB，先抑制再限制最后沖洗出NOB，使得AOB具有較高的數(shù)量而淘汰NOB，從而維持穩(wěn)定的亞硝酸鹽積累。短程硝化過程通常由控制溫度、溶解氧、pH來實現(xiàn)。溫度控制短程硝化的基礎在于兩類硝化細菌對溫度的敏感性不同，25℃以上時，AOB的zui大比生長速率大于NOB的zui大比生長速率。據(jù)此提出了世界上di一個工業(yè)化應用的短程硝化工藝——SHARON工藝(溫度設置為30~40℃)。因此，在低溫下實現(xiàn)短程硝化頗具挑戰(zhàn)。

With the continuous development of denitrification technology, people have put forward higher requirements for nitrification process, hoping to control the reaction products of nitrification in the nitrite stage. As a pre-treatment technology for denitrification or anaerobic ammonia oxidation, it can save aeration energy consumption and add alkali. Through a better understanding of two types of nitrifying bacteria (AOB and NOB), short-range nitrification processes have emerged. The core of this process is to selectively enrich AOB, first inhibit, then limit, and finally flush out NOB, so that AOB has a higher quantity and NOB is eliminated, thereby maintaining stable nitrite accumulation. The short-range nitrification process is usually achieved by controlling temperature, dissolved oxygen, and pH. The basis for temperature controlled short-range nitrification lies in the different sensitivity of two types of nitrifying bacteria to temperature. When the temperature is above 25 ℃, the maximum specific growth rate of AOB is greater than that of NOB. Based on this, a short-range nitrification process for industrial application in the world, the SHARON process (with a temperature set at 30-40 ℃), was proposed. Therefore, achieving short-range nitrification at low temperatures is quite challenging.

　　1.2反硝化工藝

1.2 Denitrification process

　　低溫對于反硝化有顯著的抑制作用，JichengZhong等研究了太湖沉積物中的反硝化作用，經(jīng)過數(shù)月的實驗分析發(fā)現(xiàn)反硝化速率呈現(xiàn)季節(jié)性變化。U.Welander等考察了低溫條件下(3~20℃)反硝化工藝的運行性能，研究表明在3℃下反應器的反硝化速率僅為15℃下的55%。相對于傳統(tǒng)的缺氧反硝化，溫度對好氧反硝化的脫氮效率影響不顯著，王弘宇等篩選出的一株好氧反硝化菌，在25~35℃下都能達到大于78%的脫氮效率。

Low temperature has a significant inhibitory effect on denitrification. Jicheng Zhong et al. studied the denitrification in the sediment of the Taihu Lake Lake, and found that the denitrification rate showed seasonal changes after several months of experimental analysis. U. Welander et al. investigated the operational performance of denitrification process under low temperature conditions (3-20 ℃) and found that the denitrification rate of the reactor at 3 ℃ was only 55% of that at 15 ℃. Compared to traditional anaerobic denitrification, temperature has no significant effect on the denitrification efficiency of aerobic denitrification. Wang Hongyu et al. selected an aerobic denitrifying bacterium that can achieve a denitrification efficiency of over 78% at 25-35 ℃.

　　1.3厭氧氨氧化工藝

1.3 Anaerobic ammonia oxidation process

　　有學者的研究表明，能夠進行厭氧氨氧化反應的溫度范圍為6~43℃，zuijia溫度為28~40℃。在廢水生物處理中，活化能的取值范圍通常為8.37~83.68kJ/mol，而厭氧氨氧化的活化能為70kJ/mol。因此，厭氧氨氧化屬于對溫度變化比較敏感的反應類型，溫度的降低對其抑制作用明顯。

Research by scholars has shown that the temperature range for anaerobic ammonia oxidation reaction is 6-43 ℃, and the recommended temperature is 28-40 ℃. In wastewater biological treatment, the range of activation energy is usually 8.37~83.68 kJ/mol, while the activation energy for anaerobic ammonia oxidation is 70 kJ/mol. Therefore, anaerobic ammonia oxidation belongs to the reaction type that is more sensitive to temperature changes, and the decrease in temperature has a significant inhibitory effect on it.

　　低溫對厭氧氨氧化的影響很大，受低溫抑制后需要較長時間才能恢復。厭氧氨氧化工藝的運行溫度從18℃降至15℃時，亞硝酸鹽不能被*去除，導致亞硝酸鹽的積累，對厭氧氨氧化工藝有著顯著的抑制效果，從而引起連鎖效應，使得厭氧氨氧化菌失活。J.Dosta等在研究溫度對厭氧氨氧化工藝的長期影響時，將試驗溫度由30℃調(diào)至15℃，只有氮容積負荷(NLR)從0.3kg/(m3?d)大幅降低至0.04kg/(m3?d)才能保證出水水質(zhì)。甚至經(jīng)30d的馴化仍未見好轉(zhuǎn)，將試驗溫度調(diào)回至30℃運行75d后，污泥活性僅為0.02g/(g?d)，處于較低水平。

Low temperature has a significant impact on anaerobic ammonia oxidation, and it takes a long time to recover after being suppressed by low temperature. When the operating temperature of the anaerobic ammonia oxidation process drops from 18 ℃ to 15 ℃, nitrite cannot be removed, leading to the accumulation of nitrite, which has a significant inhibitory effect on the anaerobic ammonia oxidation process, causing a chain effect and deactivating the anaerobic ammonia oxidation bacteria. J. When studying the long-term effect of temperature on anaerobic ammonia oxidation process, Dosta et al. adjusted the experimental temperature from 30 ℃ to 15 ℃. Only when the nitrogen volumetric load (NLR) was significantly reduced from 0.3kg/(m3? D) to 0.04kg/(m3? D) can the effluent quality be guaranteed. Even after 30 days of domestication, there was no improvement. After adjusting the experimental temperature back to 30 ℃ and running for 75 days, the sludge activity was only 0.02g/(g? D), which was at a relatively low level.

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