From 30000 to 50000 TPD Without New Tanks The Dividend of In Situ Wastewater Plant Retrofit

Article Guide: Using two in situ retrofit cases from Lijiang and Chengdu wastewater plants as entry points, this article reveals the industry trend shifting from large scale demolition and construction to in situ capacity tapping for upgrade and expansion. Three driving forces are pushing aging wastewater plants toward in situ retrofit: influent concentration returning to design values, tightening discharge standards with quasi Class IV rollout, and performance based payment policies taking effect. Small and medium sized plants face four key bottlenecks: lack of calculation tools, chaotic media market, complex retrofit processes, and insufficient technical support. Tongxiang Small Boss has transformed from a media supplier into a wastewater treatment bioengineering service provider, offering one stop service across four pillars: solutions, process design, media, and technical support.

The First Wastewater Treatment Plant in Lijiang, Yunnan recently achieved something remarkable: without adding a single inch of process land, it converted its original CASS tanks to a pure biofilm process, expanding daily treatment capacity from 30000 to 50000 tons, while upgrading effluent standards from Class I-A to quasi Class IV. A 100000 ton scale plant in Chengdu went even further, using MBBR combined process for in situ upgrade, achieving a power consumption of only 0.32 kWh per ton of water after retrofit.

These two projects point to the same signal: in an era of land exhaustion and budget tightening, the optimal solution for wastewater plant upgrade and expansion has shifted from "large scale demolition and construction" to "in situ capacity tapping".

01 A Wave of Aging Plants Will Follow This Path

Why now? Three forces have converged.

• First, influent concentration is returning to design values: As sewer network inspection and repair progress, influent concentrations at some plants are returning to design values, meaning actual biological tank loads will gradually approach or even exceed design limits;
• Second, discharge standards are tightening: Quasi Class IV standards are being rapidly rolled out in key river basins;
• Third, payment rules have changed: In 2024, five government departments including the Ministry of Housing and Urban-Rural Development explicitly shifted from volume-based to performance-based payment, meaning unstable effluent directly impacts plant revenue.

Upgrade, expand, and do it without new land, three goals must be achieved simultaneously. Adding suspended bio media into existing tanks to multiply the total microbial mass, the biofilm process has therefore become the common choice for major projects. It can be predicted that in the coming years, a large number of aging wastewater plants built a decade ago across the country will successively embark on this path of "in situ retrofit".

02 What Works for Large Plants May Not Work for Small Ones

However, the same path presents completely different levels of difficulty for large projects versus small plants. Behind the Lijiang project were top-tier design institutes, leading engineering companies, and expert teams. The reality across the country is that there are far more small and medium sized wastewater plants, rural sewage stations, and enterprise-built wastewater stations, and when they face upgrade pressure, what holds them back is not money, but these four issues:

Simply put, what small and medium clients lack is not a truckload of media, but a partner who can manage everything from solution design to commissioning.

03 This Is Exactly What Small Boss Transformation Aims to Do

Tongxiang Small Boss Special Plastic Products Co., Ltd. has been manufacturing bio media for over two decades, and its identity has long evolved beyond just a media supplier to become a wastewater treatment bioengineering service provider, offering solutions, process design, technical support, and media, managing everything from one end to the other:

In the era of performance-based payment, what clients want is never just a truckload of media, but a biological tank that consistently meets discharge standards. On the path of upgrade and expansion, every wastewater plant needs a reliable partner.

What Small Boss is doing is enabling small and medium clients to access complete service from solution design to commissioning. This is exactly what Small Boss is working to achieve.

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