Aquaculture Wastewater Treatment with MBBR: 600 m³/d Shrimp Farm Achieves 91% Ammonia Removal for 70% Water Reuse

In high-density shrimp farming, ammonia is the invisible killer. At 35 mg/L NH₃-N in the influent and stocking densities of 250–300 shrimp per square meter, a single water quality excursion can wipe out a cycle's profit. Traditional water exchange - flushing clean water through the ponds - wastes a scarce resource and introduces pathogens. MBBR offers a different model: treat and reuse. This case study covers how a large-scale shrimp farm deployed a 600 m³/d MBBR system to strip ammonia to 3 mg/L and reuse 70% of its water, continuously.

Project Overview

In modern high-density shrimp and fish farming, maintaining water quality is critical. The client operates a large-scale shrimp farm and required stable, efficient, low-maintenance treatment. After evaluating multiple technologies, an MBBR-based biological system was selected due to superior nitrification and minimal maintenance. The core challenge in recirculating aquaculture systems (RAS) is the accumulation of toxic ammonia excreted by the shrimp. At the stocking densities employed - 250 to 300 shrimp per square meter - ammonia concentrations rise rapidly between water exchanges. Traditional flow-through systems consume enormous volumes of water and expose the stock to pathogens introduced with incoming water. MBBR addresses both problems simultaneously: it biologically oxidizes ammonia to nitrate within the recirculation loop, and by enabling water reuse, it creates a biosecure barrier against external contamination.

Design Parameters

Influent Water Quality

Process Flow

The treatment train follows a logical sequence designed to protect the biological stage and polish the effluent for safe recirculation:

Solid Separation → Equalization Tank → MBBR Aeration Tank → Sedimentation Tank → UV Disinfection → Reuse

Ammonia removal is the key challenge. MBBR solves this by providing large surface area for nitrifying bacteria, maintaining stable biofilm under changing temperatures, and allowing continuous operation without biomass washout. Fine bubble aeration ensures sufficient DO for nitrification. The protected surface area of the biofilm carriers provides an ideal habitat for slow-growing nitrifying organisms - Nitrosomonas and Nitrobacter - that would otherwise be washed out of a suspended-growth system operating at the short hydraulic retention times typical of aquaculture recirculation loops. Because the biofilm is physically anchored to the carriers, the nitrifier population remains stable even when water temperature fluctuates between harvest cycles or during seasonal transitions.

Operational Parameters

Treatment Results

Project Highlights

The MBBR system delivered results across multiple dimensions - biological performance, operational efficiency, and farm economics:

Stable Nitrification: Ammonia consistently maintained below 5 mg/L, even during feed-intensive growth phases. The biofilm carriers retained nitrifying bacteria through temperature swings and harvest cycles, eliminating the ammonia spikes that previously caused mortality events.

Reduced Water Exchange: The 70% water reuse rate cut freshwater consumption dramatically. This translated directly into lower pumping costs, reduced energy for heating or cooling incoming water, and a smaller environmental footprint.

Lower Disease Risk: By minimizing the introduction of external water, the system created an effective biosecurity barrier. UV disinfection as a final polishing step provided an additional layer of pathogen control before water returned to the ponds.

Easy Integration: The MBBR tank was retrofitted into the existing pond infrastructure with minimal civil work. The modular design meant the farm could continue operating during installation.

Lower Operating Costs: Compared to traditional flow-through systems, energy consumption dropped - fine bubble aeration is inherently more efficient than the large pumps required for continuous water exchange. Operator intervention was minimal: the self-regulating biofilm handled load variations without manual adjustment.