Activated Sludge Bulking and incentives
Abstract ֵ�� pHֵ�����������ȽǶȽ��з���,�ó���ˮˮ�ʡ�����������ͬ,�����������͵�ԭ�����Ľ���. To: Activated Sludge Bulking Activated Sludge phenomenon is a common problem and its evolution process. Describes the characteristics and classification of the phenomenon, and from the temperature, nutrient ratio, sludge loading, DO values, pH values, the perspective of the early digestion analysis, the water quality, operating conditions are different, resulting in sludge bulking conclusion for different reasons.
Keywords:: activated sludge, sludge bulking, incentives
���� 0. Introduction
�걻A1dern��Leekett����,�����侭�á��ɿ������ƶ��õ��㷺Ӧ��,������ʵ�����в����˽����������������� AB���ա� A/O���ա� A 2 /O��ϵ�б��ι���,�����������ָĽ��Ļ�������ն��ᷢ��������������,���һ������������������dz��㷺,�������������ܹ����������������,Ӱ���ˮˮ��.����������ͳ�Ϊ�������෨����������������֮һ. Activated sludge was A1dern since 1914 and Leekett invention, because of their economic, reliable and widely used advantage and produced a stage with the actual operation of aeration, decreasing aeration, AB technique, A / O process, A 2 / O, and other deformation processes, but it is in the activated sludge process which will improve the sludge bulking phenomenon and the phenomenon of activated sludge bulking very broad expansion of activated sludge to reduce sludge settling properties, affecting water quality . So as activated sludge bulking problems one of the biggest problem people.
�������������� 1. Overview of Activated Sludge Bulking
Eikelboom ����������ƽ��ֱ���Ĵ�С������ �ֳɴ�(>500 �� m) ����(150-500 �� m) ��С(<15O �� m) ���� �ȼ�,����ߴ粻ͬ������,���������ٶ��кܴ����.����ij���������Ҫ�������ݻ�ָ��( SVI������,���õĻ��������SVIֵС��100ml/g [ 1 ] . Sludge Activated Sludge Bulking refers to volume expansion, water rate, easy to precipitate. Eikelboom by the floc size of the average diameter of the sludge into large (> 500 �� m), the (150-500 �� m), small (<15O �� m) three levels of different sludge floc size, settling speed of the interface is very different. sludge settling performance depends mainly on sludge volume index (SVI to describe, a good activated sludge SVI value of less than 100ml / g [1].
] :��˿״�����������������,˿״���ܳ��ȴ���lx10 4 m �� g��,�� ������ɢ,�������ָ���ϴ�,һ����ΪSVIֵ����200���־�Ѳ�����������,�۳������ܲ�,��������ٶ�С. Activated sludge was expanded, due to the expansion of high moisture content of sludge and difficult to precipitate, resulting in the loss of more sludge. Activated Sludge Bulking often determined from the following aspects [2]: �� sludge bulking caused by filamentous bacteria in The total length of filamentous bacteria is greater than lx10 4 m / g, etc., �� loose sludge, sludge volume index of large, generally believed that the SVI value of more than 200 signs have been sludge expansion, �� settlement of poor performance, regional settling velocity small.
�������������ص� 1.1 Characteristics of Activated Sludge Bulking
,������60 �� ,�¹�50 �� ,����� 50 ������ˮ������������������.�ҹ��ľ�������� �����෨���յ���ˮ��,Ҳ��ͬ�̶ȵش��������������� ,�����ձ���ǿ.������������������༰���ݱ�����ĸ��ֹ����ж�����,����Σ������.������������������ܹ����������ʧ����ˮ������(SS)����,���յ��´����������[ 3 ] . Expansion of the sludge has the following characteristics: First, the occurrence of high risk. According to statistics, in the United States 60%, 50% in Germany, Italy, there is 50% sewage sludge bulking problem. The vast majority of our activity of sludge process wastewater treatment plant, but also to varying degrees, the phenomenon of sludge bulking, and second, universal strong. the phenomenon of sludge bulking of activated sludge and its evolution from a variety of processes are present, third, serious harm. sludge bulking After the sludge can cause the loss of the phenomenon, and the effluent suspended solids (SS) exceeded, resulting in significantly reduced processing capacity [3].
�����������͵ķ��� 1.2 Classification of Activated Sludge Bulking
There are two types of activated sludge bulking: First, expansion of activated sludge filamentous bacteria, due to the large population of filamentous bacteria caused by expansion of activated sludge filamentous bacteria, two strains of non-filamentous sludge bulking, the plastic strain groups of bacteria in vivo accumulation of high viscosity polysaccharides caused by non-filamentous bacterial expansion. In recent years, and it was found that Bacillus subtilis and Escherichia coli can cause sludge bulking phenomenon.
1.2.1 Expansion of filamentous bacterial
����ɢ)�Ľṹ,��ϸ����˿״������,�γ�ϸ��������[ 4 ] .�ڽ���˿״��������������,�ж��ֽ��ͷ���:�١� (A �� V)��˵.�����Һ�л����ܵ����ƻ����ʱ,���ڱȱ�������˿״����ȡ���ʵ�����Ҫǿ�ھ�����,����������ܵ�����,˿״���ܹ�������ֳ,ռ��������λ,���յ�����������,�ڡ�ѡ��������.��������������������ѧΪ����,���ݲ�ͬ����������в�ͬ������������ʺͱ��ͳ�������˿״���������ϸ���ľ������.˿״�����е͵�����������ʺͱ��ͳ���,�ڵͻ���Ũ�ȡ� DOֵʱ���нϸߵ���������,����������պ��෴.�ۡ�������˵.�ü�˵�����������������Ϊ����,��һ���Ǿ�����ϸ��,�ڶ����Ǿ��и��������������������ͼ���˿״��,�������Ƕ��ܽ����и��������Լ����߶���еĿ���������˿״��,�ڵͻ���Ũ����,����Ũ��С��ijֵʱ,�ڶ������ォռ����,������Ũ�ȴ��ڸ�ֵʱ,ֻҪ�ܽ����Ĵ��ݲ�����������,��һ�����ォռ����,�ڸ��ʵ��ܽ��������,���������ォռ����,�ܡ� Chudoba��1985������˻��ۣ�����(AC �� RG)��˵.�ڸ߸���������,�����������ۻ��л����ʵ�����ǿ,˿״���ϲ�.����ʱ�������ܽ������ƺͿ���,����˿״����������,��ɻ���/������ѭ���Ͽ�,�����Ͽ�,�γ���������[ 5 ] . Sludge bulking caused by filamentous fungi is induced in the incentives under the cause of sludge bulking filamentous bacteria in the same competition in the floc can be caused by strong growth. Currently recognizable filamentous bulking flocs There are two types: the first class is a long filamentous bacteria sticking out from the floc, the floc of each connection, the formation of filamentous bacteria and floc network, the second is a more open (or spread) of the structure along the filamentous bacteria from the pool of bacteria, floc formation of elongated [4]. in explaining the phenomenon of filamentous bulking, there are a variety of interpretation methods: ��, (A / V) hypothesis. When the mixture is restricted or control matrix, due to large surface area The ability of filamentous fungi to obtain the matrix stronger than floc, which was inhibited floc, filamentous bacteria can multiply, the dominant, leading to sludge bulking, ��, selectivity theory. the theory to microbial growth kinetics science-based, depending on the type of micro-organisms have different maximum growth rate and saturation constant of filamentous bacteria and floc bacteria in the competition. filamentous fungi have a low maximum growth rate and saturation constant, at low substrate concentration, DO values have a higher growth rate, while the floc is just the opposite. ��, starvation hypothesis. This hypothesis will be divided into three types of activated sludge microorganisms, the first category is the floc bacteria, the second is a high substrate affinity but slow-growing filamentous bacteria resistant to starvation, the third category is the high oxygen affinity, highly sensitive to starvation rapid growth of filamentous bacteria, at low substrate concentration, substrate concentration smaller than a certain value, the second Microbe will prevail, when the substrate concentration is higher than the value, as long as oxygen delivery is not a limiting factor, the first class of micro-organisms will prevail, low dissolved oxygen in the case of high substrate, the third class of micro-organisms will prevail, �� , Chudoba in 1985 proposed the accumulation / regeneration (AC / RG) hypothesis. in the high-load conditions, the microbial floc accumulation of organic matrix capability, filamentous bacteria is poor. But this time limitation and control of dissolved oxygen by microbial , due to less aerobic filamentous bacteria to complete the accumulation / regeneration cycle faster, grow faster, the formation of sludge bulking [5].
Links to Research Papers Download http://www.hi138.com 1.2.2 Expansion of non-filamentous bacterial
] .�������ฺ�ɸ�,�����ܹ�����������Ӫ������,�������¶ȵ�,�����Ӫ�����ʴ�л�ٶ���,��ɴ����ĸ�ճ�Զ���������������������,ͬʱ���ڶ��������ʾ���ǿ��ˮ��,ʹ����������渽��ˮ�������,���Ӱ���������������ܱ��. Of non-filamentous sludge bulking occurred in the sewage sludge load relatively low water temperature is high [6]. As high sludge loading, microorganisms can absorb large amount of nutrients, but low temperature, microbial nutrient metabolism slow, resulting in a large number of high viscosity polysaccharides in microbial surface storage, and because of strong hydrophilic polysaccharides, so that the surface of activated sludge attached to the water greatly increased, thus affecting the performance of activated sludge settling worse.
1.2.3 Factors other species
This year, it was found, such as E. coli, Bacillus subtilis, also can cause sludge bulking. Although E. coli bacteria, but it is sometimes shaped into a chain, but also can cause sludge bulking, sludge bulking caused by B. subtilis is due to growth in its a particular phase due to the formation of the chain-like morphology.
�������͵�Ӱ������ 3. Sludge Bulking Factors
�¶� 3.1 Temperature
[ 7 ]�����о�����,�ϵ��¶�������˿״��������.�������10 ��ʱ������˿״����������������,����ˮ�¶���ߵ�22 �����ٲ�����������. Each bacterium has its optimum growth temperature range. Daigger [7], who studies have shown that lower temperatures favor the growth of filamentous fungi. Results showed that at 10 �� easily lead to sludge bulking phenomenon of filamentous fungi, and sewage temperature is raised to 22 �� is no longer produced expansion.
Ӫ������ 3.2 percentage Nutrition
: N : P �� 100 : 5 : 1Ϊ��������˱���.�����ˮ�и�Ӫ���ɷֲ�������ñ���ʱ����ܵ�����������.����R �� Generally considered wastewater BOD 5: N: P = 100: 5: 1 ratio for the appropriate microbes. If the water does not meet the various nutrients may result when the ratio of sludge bulking. For example R. �� E. ���˱�������ȱN�������,����˿״����N �� P��Ӫ�������н�ǿ������,�ڸ���Ӫ������Ũ�Ƚϵ͵�����¶������ۻ�����,��˲�������˿״��������,���������������ܵ�N �� P�����ƶ���˿״�������,�����������. Sheder, who reported the case of the missing N, due to filamentous fungi on N, P and other nutrients has a strong affinity, low concentration of nutrients in such cases has accumulated on its ability to inhibit the wire can not like the growth of bacteria, and other kinds of microorganisms is limited by N, P restrictions gradually replaced by filamentous fungi, resulting in sludge bulking.
���ฺ�� 3.3 sludge load
ͨ���Զ����ˮ����������о�,�������ฺ����0.25 �� 0.45kg ( BOD 5 �� kg ( MLSS .d��Χ�ڲŲ���������������,���ڻ����������������ܵ�����������. Most people think low load likely to cause sludge bulking. Because in the low load condition, floc bacteria on the absorption of nutrients is limited, and filamentous fungi than floc bacteria have a greater surface area, in the low load predation has a stronger following. but some people think that only in a range of sludge loading was unlikely to cause sludge bulking phenomenon. Pipes on a number of sewage treatment plants through Research, found that the sludge loading in the 0.25 ~ 0.45kg ( BOD 5 / kg (MLSS. d range was not easy to cause sludge bulking, lower or higher than the range of capital may lead to sludge bulking.
�ܽ���ֵ DO value 3.4
Ҳ�ǵ����������͵�����.�������Ϊ�ܽ���Ũ�ȵ�ʱ���� ˿״���Ⱦ�����ϸ���и��ߵ��ܽ���������������,����ڵ���������˿״���Ⱦ�����ϸ���и�ǿ�ľ�����,�������ܽ���Ũ�ȵ͵�������������������. Dissolved oxygen (DO) also contributed to the bulking factor. Most of that low dissolved oxygen concentrations than the filamentous bacteria floc has a higher oxygen affinity and endurance, so the wire under hypoxia floc-like bacteria than the bacteria more competitive, so in the case of low dissolved oxygen concentration could easily lead to sludge bulking.
ֵ 3.5 pH value
ֵ��Χ��6.5-8.5 [ 8 ] ,��pHֵ����6.0ʱ,�������ܵ�����,���ڸ�pH��Χ������������ķ�ֳ,�����͵�4.5ʱ�������ȫռ������,������ԭ��������ʧ,����������ƻ�,���յ���������������. Floc suitable pH range is 6.5-8.5 [8], when the pH value below 6.0, its growth was inhibited, whereas in the pH range is conducive to the propagation of fungi, when reduced to 4.5 when the fungus is completely occupied advantage, protozoa floc disappeared, the destruction of sludge flocs, resulting in sludge bulking phenomenon.
�������� 3.6 Early digest
Sewage treatment plant effluent into the sewage pipes in the city before or stay too long in the pretreatment area that can happen to family reaction to produce sulfide, etc., and when the water is high in sulfur content of sulfur can lead to a variety of wire and other bacteria overgrowth, leading to sludge bulking.
���� 4. Conclusion
Is the activated sludge bulking has plagued people since the advent of the problem. Current human studies of sludge bulking Although there has been some achievements, but because of water quality and sewage all over the different operating conditions, the phenomenon caused by the factors of Activated Sludge Bulking varied, so it has not had a way to apply to all phenomena of sludge bulking in a reasonable explanation. only with local conditions to address water, operating conditions and other factors to consider before making a targeted explanation.
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