Operation, maintenance and management of the hotte

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Operation, maintenance and management of large-scale urban sewage treatment plants in Denmark (middle)

2.1 basic information

Lynette, damhus? EN, Lundtofte and aved? Re sewage plants are all located on the island of Sealand, Denmark, Be responsible for the treatment of urban sewage and industrial wastewater in the surrounding administrative areas [4,5. In 2004, the treatment load and influent load of the sewage plant are shown in Table 2.

Lynette is the largest urban sewage treatment plant in Denmark, with a design treatment capacity of 150000 tons/day. In 2004, the actual influent load was nearly 200000 tons/day, and the linearity of the sensor element reached a very high water standard. Damhus? En is the third largest urban sewage treatment plant in Denmark, with a design treatment capacity of 70000 tons/day. Damhus? En and Lynette belong to Lynette? Llessk Operation and management of abet (Lynette associates). Aved? Re is the fifth largest sewage treatment plant in Denmark, with a design treatment capacity of 64000 tons/day, belonging to spildevandscenter aved? Re (aved? Re sewage Center) operation and management. Lundtofte is relatively small, with a design processing capacity of 22000 tons/day

the above four sewage mortar tensile testing machines are a new generation of testing machines developed according to the dry powder mortar tensile testing standard. See Table 3 and table 4 for the water quality characteristics and effluent conditions of the water plant

after analyzing the influent water quality, it is found that the results of the experiments of four sewage plants can be used as an important reference for the height of finished product packaging boxes stacked in the factory or for the design of packaging boxes. According to the cod/bod5 value of influent water quality, it belongs to the medium and low range of [6 in the literature, which may be related to the inflow of industrial wastewater. After summary, it is found that the cod/tn and cod/tp of Danish urban sewage are in the literature [6 within the range of medium and high values specified.

it is found that the effluent indicators of key pollutants of the four urban sewage plants are lower than the relevant requirements of the EU 91/271/eec act and the Danish environmental protection department.

2.2 process flow

the process of the Danish urban sewage treatment plant can generally be divided into three parts: sewage treatment unit, sludge and waste treatment unit and waste gas treatment unit. Lundtoft sewage plant is a very typical city in Denmark Sewage treatment plant. The following discussion is based on the process flow of Lundtofte sewage treatment plant. The specific process flow of Lundtofte sewage treatment plant is shown in Figure 2

2.3 sewage treatment unit

2.3.1 mechanical treatment

for urban sewage plants, sewage mechanical treatment usually includes coarse grid, aerated grit chamber, fine grid, primary sedimentation tank and secondary sedimentation tank. Since the design of various mechanical treatment processes has become very successful, as mainstream manufacturers such as 3-star and LGD reduce the supply of external panels, there is no need to discuss in detail. However, it is worth learning and using for reference to deal with the waste and waste gas generated in the mechanical treatment process

before entering the aeration tank, a series of mechanical treatment processes will produce a large amount of waste. The practice of large-scale urban sewage plants in Denmark is that solid waste is not mixed with excess sludge into the anaerobic digestion tank, but directly into the sludge incinerator for incineration after dehydration. This is because the inorganic content of such solids is relatively high, and directly entering the digestion tank will affect the anaerobic digestion effect. In addition, this kind of waste has not been used for recycling in construction, mainly because this kind of sand contains heavy metals and persistent organic substances, which are potentially harmful to human health

large urban sewage treatment plants in Denmark attach great importance to the collection and treatment of waste gas generated by aeration or agitation during mechanical treatment. Generally speaking, the aerated grit chamber is capped with aluminum materials. The primary sedimentation tank of some sewage plants will also be capped. The gas produced in the treatment process, such as H2S, will also enter the incinerator along with the specific gas pipeline for treatment

2.3.2 biological treatment

as mentioned above, the biological treatment process of sewage from large urban sewage plants in Denmark is very similar. The above four sewage plants all adopt biodenitro or biodenipho process. The following is a brief introduction to these two processes process introduction

biodenitro and biodenipho processes are patented technologies of Kr ü ger company in Denmark. This technology is characterized by high degree of automation, small floor area, and good removal effect of organic matter, nitrogen and phosphorus. Different from the biodenitro process, biodenipho adds an anaerobic tank in front of it, so it has the function of biological phosphorus removal. Biodenitro, on the other hand, cannot remove phosphorus biologically, and can only remove phosphorus chemically

next, take the biodenitro process as an example, and focus on the operation and control of this process

The operation of biodenitro process is based on Oxidation Ditch Technology (Danish urban sewage plants mostly use oxidation ditch technology based on surface exposure). Usually, the two oxidation ditches are divided into a group and operated in the way of alternating aeration to achieve the purpose of nitrification and denitrification. The biodenitro process is divided into four stages, as shown in Figure 3. Among them, it is worth noting that the main purposes of setting stage B and stage D are two: first, to remove the residual ammonia nitrogen in the anoxic tank in the first stage; Second, because nitrification takes a relatively long time, in order to achieve better effluent standards

generally speaking, although biodenipho process has strong biological phosphorus removal function, the sewage plant will still assist in using chemical phosphorus removal method to achieve better effluent TP concentration. This is especially true for sewage plants using biodenitro process. The substance to be put is generally FeCl3 or AlCl3, and the place to be put is set in front of the aeration tank. A phosphorus monitoring device is installed behind the aeration tank, which will automatically add phosphorus removal when the TP concentration exceeds the standard control system

the above four large urban sewage treatment stations

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