The scale of Taiyuan southcity WWTP reached 200,000 m³/d after retrofitting on September 25 2019，indicating the complete success of the upgrading project. SPRING was responsible for the  retrofitting of the biochemical tank applying MBBR process under the specific requirement of non-stop production. The successful implementation of the non-stop production retrofitting in the project marks the high level of the design and construction of MBBR process provided by SPRING, provides a new option for the upgrading of the WWTP facing similar challenges and problems.

In recent years, the Fen river was polluted by the initial rain, river sediment, agricultural and rural sewage, which impaired self-purification function. In order to improve the water quality of the Fen River, relevant departments of Taiyuan City organized a special meeting in 2019 to discuss the sustainable development ideas of system governance and long-term governance, and planned to upgrade main WWTPs in Taiyuan City. The Grade A of national WWTP discharging standard was upgraded to Shanxi Province's Integrated Wastewater Discharge Standard (DB14/1928-2019), and the effluent of WWTP should reach quasi-surface water Class V.

Taiyuan southcity WWTP was one of the key projects in this batch. The original process was AAO. The upgrading project required the enhancement of removal efficiency of major pollutants, especially ammonia nitrogen. The retrofitting period coincided with the second National Youth Games hosted by Taiyuan City, which ordered the plant to operate at full capacity. At the same time, the project faced many challenges such as insufficient landuse, difficult implementation, strict time limit(less than 50 days) and the influence of rainy season. SPRING MBBR non-stop production retrofitting technology was finally selected after scientific verification and selection from various decision makers.

Considering the hardness of the project, SPRING spared no effort and simulated details of impletion, focused on the quality control. The project was finally completed 5 days ahead of the original plan through the rational use of installation technology and scientific deployment. It only took 40 days to complete the retrofitting of all 4 series of biochemical tank without any reduction on scale. The effluent water quality reaches the standard steadily after commissioning. The retrofitting project was completed before the National Day and was regarded as the gift project for National Day under the cooperation of local government, the general contractor, the supervision unit and SPRING.

SPRING, with advanced technology as the propeller, takes vast project implementation experience as the sail, always adheres to the core value of customer-centered, and work together with clients to fulfill the responsibility of environmental protection enterprises for sustainable development of the environment, creating the harmony between human and nature!

Recently, SPRING has received many inquiries from clients and business partners on "non-stop production retrofitting technology". So here comes the reply and summary:

      1.Whether the non-stop production retrofitting will extend the period of the project?

The non-stop production MBBR retrofitting not only doesn’t extend the retrofitting period, but also will effectively shorten the retrofitting period since there is no need of increased civil works and dredging work. Multiple series of biochemical tanks can be retrofitted simultaneously under the normal operation condition. The larger quantity of biological tanks, the more obvious the advantages of non-stop production retrofitting to shorten the retrofitting period. Taking Taiyuan south city WWTP with the capacity of 200,000 m³/d as an example, if the four series of biochemical tanks are retrofitted under the condition of off-production, the whole period will be about 160 days, while the construction period of the non-stop production retrofitting is only 40 days. Therefore, the non-stop production retrofitting will not extend the overall construction period, besides, it can ensure the normal operation and income of the sewage treatment plant during the retrofitting period.

Table 1 Comparison of two ways of retrofitting

      2.Will the retrofitting cost or expense be greatly increased applying non-stop production retrofitting?

From the comprehensive comparison between the retrofitting cost and the loss of revenue during retrofitting, the overall cost of the non-stop production retrofitting won’t be significantly increased.

If the off-production retrofitting is adopted, the WWTP will save part of the retrofitting construction cost, but it will lost operating gains(especially for WWTPs with BOT mode). The non-stop production retrofitting is the opposite of the off-production retrofitting.

      3. Will the quality of non-stop production retrofitting meet the requirements?

The same process effect and quality standard can be achieved through non-stop production retrofitting. SPRING has accumulated vast experience of more than 160 projects including process design, implementation and commissioning of WWTPs with different scale, processes and tank configuration. Based on the implementation conditions of non-stop production retrofitting, SPRING innovates the fixed installation methods of sieve, aeration system and other equipment, optimizes the installation procedures, saves the retrofitting time and guarantees the installation quality. Through computational fluid dynamics simulation and calculation, the installation structure strength can be guaranteed.

      4.How to ensure the fluidization of suspended carrier fillers under non-stop production retrofitting?

SPRING has rich experience in design, process implementation and other aspects of non-stop production retrofitting. SPRING will specifically design the tank configuration according to the specific situation of each project, and guarantee the uniform fluidization of the suspended carrier through hydrodynamics simulation. In the process of retrofitting, the professional project implementation team can ensure the accurate installation of sieve, aeration system and other equipment, and ultimately ensure the stable operation of the system. At present, SPRING has completed a number of non-stop production retrofitting projects

      5.How to guarantee the construction period of non-stop production retrofitting?

Firstly, SPRING innovates the installation methods of interceptor system, aeration system and other equipment, optimizes the installation procedures, completes the prefabrication in the company, and therefore saves the time of on-site installation. Secondly, SPRING repeatedly deduces the process implementation and strictly grasps the quality of the process implementation reasonably uses the installation technology and scientifically arranges the construction period, works closely with all units on the project site to guarantee the construction period. For example, Taiyuan south city WWTP, with a scale of 200,000 m³/day and four series of biochemical tanks, was originally arranged to with a 45-day transformation period, but finally SPRING completed the MBBR process retrofitting in only 40 days.

      6.Does SPRING only conduct non-stop production retrofitting once?

At present, SPRING has successfully completed the Taiyuan south city, Shanxi yuncheng linyi, Zhejiang lishui, Tianjin port east and other non-stop production retrofitting projects.

     7.If there are several series of biochemical tanks in a WWTP, and MBBR is applied to carry out the transformation one by one, the wastewater of the off-production tank could be conveyed to other series which can be seen as the similar form of non-stop production, is there any difference between this situation and non-stop production as you said above?

One-by-one retrofitting using MBBR is a traditional way to improve the performance of the original biochemical tank, the series under retrofitting has to stop production for dozens of working days, therefore other series have to bear overloading pollutants. This is not the real meaning of the non-stop production. In addition, with the development of society, many sewage plants operate at full load and do not have the conditions for alternate operations. Therefore, the non-stop production retrofitting can truly meet the requirements of transformation under the condition of full load of sewage plants.