UV in Indian Aquaculture: Shrimp Farms, Hatcheries & the Vibrio / WSSV Kill Curve

India is the second-largest aquaculture producer in the world, with an annual fish and shrimp production exceeding 8 million tonnes. Andhra Pradesh, West Bengal, Tamil Nadu, Odisha, Kerala, and Gujarat account for the majority of production across freshwater fish culture (catla, rohu, mrigal), shrimp farming (Litopenaeus vannamei, P. monodon), and increasingly, Recirculating Aquaculture Systems (RAS) for high-value species like salmon trout, barramundi, and ornamental fish.

Disease outbreaks driven by waterborne pathogens are the single largest cause of production loss in Indian aquaculture — costing the industry an estimated ₹15,000–25,000 crore annually in mortality, stunted growth, and antibiotic treatment costs. UV water disinfection addresses the root cause of waterborne disease spread: pathogen-laden water entering ponds, tanks, and recirculating systems. This guide covers the science and practice of UV disinfection in Indian aquaculture from hatchery through grow-out.

Fish Pathogens and UV Inactivation

Aquaculture water carries a range of bacterial, viral, parasitic, and fungal pathogens. UV disinfection at 254 nm is highly effective against bacterial and viral pathogens — less so against parasitic cysts and fungal spores, which require higher doses or complementary treatment. The key pathogens in Indian aquaculture and their UV dose requirements:

Table 1: UV Dose Requirements for Key Aquaculture Pathogens (254 nm, 4-log reduction)

Pathogen	Disease Caused	Affected Species	UV Dose (4-log)
Aeromonas hydrophila	Bacterial haemorrhagic septicaemia, ulcers	Catla, rohu, carp, tilapia	~6 mJ/cm²
Vibrio harveyi / V. anguillarum	Vibriosis (luminescent bacteriosis in shrimp)	L. vannamei, P. monodon	~6–10 mJ/cm²
Pseudomonas fluorescens	Fin rot, bacterial gill disease	Most freshwater species	~10–15 mJ/cm²
Flavobacterium columnare	Columnaris disease (saddleback)	Catfish, carp, tilapia	~15–25 mJ/cm²
White spot syndrome virus (WSSV)	White spot disease (most economically devastating shrimp disease)	All penaeid shrimp	~40–60 mJ/cm²
Infectious hypodermal and haematopoietic necrosis virus (IHHNV)	Runt deformity syndrome in shrimp	L. vannamei	~30–50 mJ/cm²
Ichthyophthirius multifiliis (Ich)	White spot disease (freshwater fish)	Carp, ornamental fish	Theronts (free-swimming stage): ~40 mJ/cm²; cysts are resistant

For shrimp hatchery applications where WSSV and IHHNV are the primary concerns, a UV dose of 60–80 mJ/cm² is the standard specification. For freshwater fish hatchery make-up water where bacterial pathogens are the main risk, 40 mJ/cm² is generally adequate. For RAS recirculated water, the UV dose is typically set at 40 mJ/cm² for bacteria and 80 mJ/cm² for facilities where viral disease is a documented historical problem.

Why UV Is Safe for Fish, Shrimp, and Biofilters

A common misconception among aquaculture operators who encounter UV for the first time is that UV radiation must be harmful to fish or shrimp if it kills bacteria. This is incorrect — and understanding why is important for proper system design.

UV disinfection occurs inside a sealed reactor. The UV lamp is enclosed in a quartz sleeve, inside a stainless steel or PVC chamber. Water flows through the reactor, receives its UV dose in milliseconds, and exits the reactor back into the aquaculture system. Fish, shrimp, eggs, and larvae never enter the UV reactor — they remain in the tanks and ponds. Only the make-up water and (in RAS) recirculated water passes through the UV unit.

Furthermore, UV radiation at 254 nm does not produce any chemical residual. The water chemistry after UV treatment is identical to before treatment — no chlorine, no ozone, no pH shift, no dissolved oxygen reduction. Fish entering a tank supplied with UV-treated water are not exposed to any UV radiation and are not affected in any way by the treatment the make-up water received.

UV also does not kill the nitrifying bacteria (Nitrosomonas, Nitrospira) that are essential in biofilter media for converting toxic ammonia to nitrite and then to nitrate in RAS systems. The biofilter is a separate component from the UV reactor; water flows through biofilter media (where bacteria are attached to surfaces, not free-floating), then through the UV reactor (where any planktonic bacteria including pathogens released from the biofilter are inactivated). The nitrifying bacteria in the biofilter are never exposed to UV radiation.

UV Application Points in Aquaculture Systems

Make-Up Water Disinfection

Every aquaculture facility — whether earthen pond, concrete tank, or RAS — adds fresh water to compensate for evaporation, seepage, and water changes. This make-up water is a primary entry point for waterborne pathogens. A UV system on the make-up water line (sized to the maximum make-up flow rate) ensures that no pathogens enter the facility through this route.

For a shrimp hatchery drawing from a borehole, the make-up water UV system requires UV dose to match the worst-case UVT of the borehole water. Groundwater typically has UVT of 80–95% at 254 nm — high, which makes UV very efficient. Turbid surface water (river, canal) has UVT of 40–70% and requires pre-filtration before UV to raise UVT and reduce the lamp count needed.

RAS (Recirculating Aquaculture System) UV Integration

In a RAS, 90–99% of the water is recirculated — only 1–10% is replaced with fresh make-up water per day. The recirculated water passes through a treatment train between uses:

Fish tank outlet → Drum filter (mechanical solids removal) → Biofilter (ammonia/nitrite conversion) → CO₂ degassing → UV disinfection (254 nm) → Oxygenation (if needed) → Fish tank inlet

The UV reactor is positioned after the biofilter because: (a) the biofilter removes fine particles (TSS) that would reduce UVT and waste UV output; (b) pathogens that colonise the biofilter media are shed into the water as it passes through, and the UV reactor immediately downstream inactivates them before they re-enter the fish tank.

UV dose in a RAS is typically set at 40–80 mJ/cm², applied to 100% of the recirculated flow at each pass. Since water recirculates through the UV reactor multiple times per day (a typical RAS circulates its full volume 5–20 times per day), the cumulative UV exposure each pathogen receives is very high — providing a high safety margin even at lower single-pass doses.

Hatchery Broodstock and Larval Water Treatment

Hatchery water — used for broodstock conditioning, egg incubation, and larval rearing — carries the highest pathogen risk in any aquaculture operation. Introduction of a pathogen at the hatchery stage destroys the entire production cycle. UV disinfection in hatcheries is applied at every water input point:

Seawater intake (marine hatcheries): Seawater is pre-filtered through multimedia filters (sand, gravel) to remove suspended solids, then UV-treated at 60–80 mJ/cm² before entering hatchery tanks. Seawater UVT is typically 85–95% in clear offshore water, lower in inshore water with turbidity.

Maturation and spawning tank water: Water for broodstock shrimp conditioned for spawning is UV-treated at 80 mJ/cm² — higher dose to ensure WSSV and IHHNV are eliminated from the water that broodstock are bathed in.

Egg incubation water: UV-treated at 80 mJ/cm² — nauplii (newly hatched larvae) are too small to be harmed by pathogens in the incubation water, and any pathogen load dramatically increases larval mortality.

UV System Sizing for Aquaculture Applications

Table 2: UV System Sizing for Common Aquaculture Applications in India

Application	Flow Rate	Water Source	Typical UVT	UV Dose Target	Philips Lamp Specification
Shrimp hatchery make-up water	1–10 m³/h	Seawater / filtered borehole	85–95%	80 mJ/cm²	2 × Philips TUV 36W
Freshwater fish hatchery make-up	2–15 m³/h	Borehole / filtered river	80–92%	40 mJ/cm²	1–2 × Philips TUV 55W
RAS recirculation (small, 50–200 m³ system)	10–50 m³/h	Recirculated fish tank water	75–88%	40 mJ/cm²	2–4 × Philips TUV 55W or 95W
RAS recirculation (large, 200–1,000 m³)	50–200 m³/h	Recirculated fish tank water	75–88%	40 mJ/cm²	Multiple parallel reactors
Ornamental fish breeding unit	0.2–2 m³/h	Dechlorinated municipal / borehole	88–95%	40 mJ/cm²	1 × Philips TUV 16W or 25W
Pond freshwater intake	5–50 m³/h	Canal / river (pre-filtered)	65–80%	40–80 mJ/cm²	2–6 × Philips TUV 95W

Pre-Treatment Before UV in Aquaculture

UV disinfection performance in aquaculture water is determined by UVT — and aquaculture water is rarely as clear as pharmaceutical or municipal water. The main pre-treatment steps required before UV in aquaculture applications:

Table 3: Pre-Treatment for UV in Aquaculture Water by Source Type

Water Source	Typical Problem	Pre-Treatment Required	UVT After Pre-Treatment
Seawater (offshore/clear)	Algae, plankton	Drum filter (100 µm) + cartridge filter (20 µm)	88–95%
Seawater (inshore/turbid)	TSS, algae, sediment	Settling → sand filter → cartridge filter	80–90%
Borehole / groundwater	Iron, manganese, hardness	Aeration → sand filter → iron removal filter	85–95% (after iron removal)
River / canal water	High TSS, organics, colour	Coagulation/flocculation → settling → sand filter → cartridge filter	70–85%
RAS recirculated water	Fine particles, TAN, bacteria from biofilter	Drum filter (40–80 µm) → biofilter	75–88%

UV Disinfection and Antibiotic Use Reduction in Indian Aquaculture

The Indian aquaculture sector — particularly shrimp farming in Andhra Pradesh, Tamil Nadu, and Gujarat — has faced export rejections and regulatory scrutiny due to antibiotic residues in shrimp destined for European, US, and Japanese markets. Tetracyclines, chloramphenicol, and fluoroquinolones detected in Indian shrimp exports are largely driven by the practice of using antibiotics to control bacterial disease outbreaks that UV disinfection could prevent.

The MPEDA (Marine Products Export Development Authority) and CIBA (Central Institute of Brackishwater Aquaculture) both recommend UV disinfection as a disease prevention measure in aquaculture as part of the national strategy to reduce antibiotic use and improve export compliance. For export-oriented shrimp farms seeking to supply EU, US, or Japanese buyers who impose zero-tolerance antibiotic limits, UV water treatment is not optional — it is a prerequisite for obtaining the microbiological control that makes antibiotic use unnecessary for routine bacterial disease prevention.

Can UV disinfection prevent white spot syndrome virus (WSSV) in shrimp?

Yes, UV disinfection at 60–80 mJ/cm² applied to all make-up water (seawater intake) prevents WSSV from entering the farm through the water supply. WSSV is present in coastal seawater in endemic areas, and water-borne transmission through the intake is the primary route of entry into shrimp ponds and hatcheries. UV at the intake is the critical control point. However, UV does not protect against WSSV transmission through infected broodstock, carrier birds, contaminated equipment, or infected wild crustaceans entering open ponds. A complete biosecurity programme — UV water treatment + SPF (specific pathogen free) broodstock + pond netting + equipment sanitation — is required for effective WSSV prevention.

Will UV kill the bacteria in my biofilter?

No. UV reactors in a RAS treat only the water flowing through the reactor — not the biofilter media itself. Nitrifying bacteria (Nitrosomonas and Nitrospira) in a biofilter are attached to media surfaces and are not in the flowing water stream that passes through the UV reactor. The UV reactor is installed downstream of the biofilter, inactivating planktonic bacteria (including pathogens) that were shed by the biofilter into the water. The attached biofilm on the biofilter media is not affected. This is why UV position in the RAS treatment train — always after the biofilter, never before it — is critical.

What UV dose is needed for shrimp hatchery water?

Shrimp hatchery water requires a UV dose of 80 mJ/cm² at the measured UVT of the pre-treated intake water. This dose achieves >4-log (99.99%) reduction of Vibrio (the primary bacterial pathogen in marine hatcheries) and 2–3-log reduction of WSSV and IHHNV in the free water phase. The 80 mJ/cm² dose is typically delivered at a flow rate of 2–8 m³/h using 2–4 Philips UV-C lamps in a single multi-lamp reactor or series configuration. Alpha UV System provides UVT-corrected sizing for each hatchery application — the lamp count and reactor size are confirmed from a measured UVT sample of the actual pre-treated intake water.

Is UV practical for large-scale pond culture (10+ hectare farms)?

For large earthen pond culture systems with high water exchange rates (5–20% of pond volume per day), UV disinfection of the full intake volume is practical and cost-effective when the pump flow rate is manageable (typically 10–100 m³/h per pond cluster). For very large farms with multiple intake points at high flow rates, UV on the main intake header plus pre-filtration is the preferred approach — treating 100% of incoming water at the point of entry rather than treating individual pond inlets. Alpha UV System has supplied UV systems for shrimp farms in Andhra Pradesh with intake flows of 50–200 m³/h across multiple pump stations.

Standards, authorities & further reading

External references used to inform this guide. Regulations evolve — check the latest revision on each authority's site before compliance decisions.

• Central Pollution Control Board (CPCB), Government of India
• Central Ground Water Board (CGWB)
• BIS IS 10500:2012 — Drinking Water Quality Specification
• WHO — Guidelines for Drinking-water Quality (4th ed.)
• NSF/ANSI 55 — Ultraviolet Microbiological Water Treatment Systems