Question map
With reference to the role of biofilters in Recirculating Aquaculture System, consider the following statements : 1. Biofilters provide waste treatment by removing uneaten fish feed. 2. Biofilters convert ammonia present in fish waste to nitrate. 3. Biofilters increase phosphorus as nutrient for fish in water. How many of the statements given above are correct?
Explanation
The correct answer is Option 2 (Only two). This is because statements 1 and 2 are scientifically accurate regarding the function of biofilters in a Recirculating Aquaculture System (RAS), while statement 3 is incorrect.
- Statement 1 is correct: Biofilters play a crucial role in waste treatment. While mechanical filters remove large suspended solids, biofilters house microbial communities that break down organic wastes, including dissolved organic compounds from uneaten fish feed.
- Statement 2 is correct: This is the primary function of a biofilter. Through the process of nitrification, specialized bacteria (like Nitrosomonas and Nitrobacter) convert toxic ammonia, excreted by fish, into nitrite and then into relatively harmless nitrate.
- Statement 3 is incorrect: Biofilters do not aim to increase phosphorus. In fact, excessive phosphorus can lead to algae blooms and water quality degradation; RAS designs typically focus on removing or managing phosphorus rather than increasing it as a nutrient.
PROVENANCE & STUDY PATTERN
Full viewThis is a 'Technology in Agriculture' question masquerading as Environment. While Statement 2 is basic static ecology (Nitrogen Cycle), Statements 1 and 3 require understanding the engineering process flow of RAS. Strategy: When a tech like RAS/Biofloc is in the news, don't just read the benefits; look up the 'schematic diagram' to see which component does what.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- Statement 1: Do biofilters in recirculating aquaculture systems remove uneaten fish feed (solid particulate waste)?
- Statement 2: Do biofilters in recirculating aquaculture systems convert ammonia from fish waste to nitrate via nitrification?
- Statement 3: Do biofilters in recirculating aquaculture systems increase phosphorus concentrations in the culture water as a nutrient for fish?
- Explicitly states particulate waste is removed by filtration (separately) before nitrification.
- Implies particulate removal is a different step from biofiltration (which handles nitrification).
- Defines the role of biological (bio)filters as transforming dissolved toxic compounds (ammonium, nitrite) to nitrate.
- By specifying dissolved-N transformation, it implies biofilters treat dissolved waste, not solid particulates like uneaten feed.
- Refers to evaluation of nitrification rates of microbead and trickling filters, indicating these biofilters are for nitrification (dissolved nitrogen removal).
- Supports distinction between biofilters (nitrifying) and mechanical/physical filters for particulates.
Defines fish farming as raising fish in tanks/enclosures where feeding occurs — implying production of feed-related wastes in such systems.
A student could combine this with knowledge of tank systems to ask which components (mechanical vs biological) handle different waste types.
States that feeding of stocked fish can pollute the environment, linking fish feed to waste and water-quality problems.
One could infer that aquaculture systems need waste-management components and then check whether biofilters address particulate versus dissolved wastes.
Lists bioremediation (use of microbes) as a method to degrade environmental contaminants and solid waste.
Since biofilters rely on microbial processes, a student could explore whether microbial treatment targets dissolved compounds or also degrades solid particulates like uneaten feed.
Gives a list of on-site nutrient and algae removal techniques including filters and sludge removal, distinguishing mechanical removal (filters/sludge) from other treatments.
A student could use this to hypothesize that physical filters/sludge removal handle solids, and then investigate whether 'biofilters' are listed among physical or biological treatments.
Explains eutrophication from inputs of nutrient-rich wastes (sewage, solid/liquid waste), linking organic/solid inputs to problems caused by dissolved nutrient release.
A student could reason that uneaten feed may produce dissolved nutrients (causing eutrophication) after breakdown, and then ask whether biofilters remove the dissolved products or the original particulates.
- Explicitly names 'nitrification of ammonia under aerobic conditions' as a process that transforms ammonia.
- Links nitrification with production/release of nitrogen oxides, showing biochemical conversion of ammonia in aerobic environments.
- States that bacteria synthesize nitrates and that nitrogen is returned as ammonia through excretion/death, implying microbial conversion between ammonia and nitrate.
- Connects bacterial activity to formation of nitrate from biologically available nitrogen forms.
- Mentions ammonia and nitrate as key inorganic nutrients in aquatic systems, establishing that both species coexist in water environments.
- Provides context that aquatic environments contain the chemical species involved in nitrification.
- Explicitly describes the role of biological (bio)filters in RAS as transforming nitrogenous wastes (ammonium, nitrite) rather than creating nutrients like phosphorus.
- Implies biofilters focus on nitrogen cycling, not on increasing dissolved phosphorus concentrations for fish.
- Describes biofiltration by plants (a type of nutrient removal strategy) that converts nutrient-rich effluents into plant biomass which can be removed.
- Implies biofiltration tends to assimilate and remove nutrients from the culture water rather than increase them.
Fishmeal/manure contains substantial phosphorus (3.0–5.0%), so feed and fish waste are sources of P in aquaculture systems.
A student could combine this with knowledge that feed/waste enter recirculating tanks to suspect biofilters must manage P loads from feed.
Lists on-site P-elimination methods including flocculation/flotation, filters and P-adsorbers, implying engineered filtration can remove phosphorus from water.
Use this to hypothesize that a biofilter might decrease, not increase, dissolved P unless it releases P during processing of solids.
States phosphorus is a major inorganic nutrient required by phytoplankton, showing dissolved P in culture water acts as a nutrient in aquatic systems.
Combine with awareness that dissolved P levels affect primary producers to assess whether biofilter operation changes available nutrient for fish (directly or via algae/foodweb).
Explains that nutrient enrichment, especially phosphates and nitrogen, causes algal blooms — a known consequence of increased P in water.
A student could look for blooms or increased algal biomass in recirculating systems as an indirect indicator that P concentrations are rising due to system components.
- [THE VERDICT]: Trap. Statement 2 is a Sitter (Static Ecology), but Statements 1 and 3 are technical traps testing functional specificity. Source: General Science applied to Current Affairs (RAS technology).
- [THE CONCEPTUAL TRIGGER]: Sustainable Agriculture & Blue Revolution (Pradhan Mantri Matsya Sampada Yojana).
- [THE HORIZONTAL EXPANSION]: RAS Components (Mechanical Filter vs Biofilter vs UV/Ozone); Biofloc Technology (Heterotrophic bacteria, C:N ratio); Aquaponics (Symbiosis of fish & plants); Seaweed Farming (Carbon sequestration); Cage Culture vs Pen Culture.
- [THE STRATEGIC METACOGNITION]: Visual Learning is key for process technologies. A simple Google Image search for 'RAS Diagram' shows a 'Drum Filter' (for solids) separate from a 'Biofilter' (for ammonia). Text-only study misses this mechanical distinction.
Uneaten feed and organic wastes introduce nutrients (N, P) that cause eutrophication in aquatic systems.
High-yield for environment questions: explains links between agricultural/aquaculture waste and water quality deterioration. Connects to topics on water pollution, aquatic ecosystem health, and management measures. Enables answers on causes of algal blooms, fish kills, and policy responses (waste control, treatment).
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Water Pollution > p. 33
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 6. Commercial Fishing & Aquaculture > p. 47
Physical removal methods such as filtration, skimming, separator thickening and sludge processing are used to remove solids and sludge from water bodies.
Useful for questions on pollution control technology and treatment options in aquatic environments. Links engineering measures (filters, skimmers) with environmental management (sludge processing, disposal). Prepares candidates to evaluate practical mitigation strategies in aquaculture and lake management.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 4.3 Rearoval of the nutrients from a lake > p. 38
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Marine Pollution Control > p. 47
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 6: Environmental Degradation and Management > Solid Waste > p. 44
Feeding stocked fish introduces organic solids and nutrients that can pollute pens, estuaries and nearby waters.
Directly relevant to questions on sustainable aquaculture and coastal management. Connects aquaculture practice to ecological impacts and regulatory/management responses, useful for policy and case-study answers.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 6. Commercial Fishing & Aquaculture > p. 47
- Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 9: Agriculture > 2. Fish Farming > p. 90
Nitrification is the bacterial aerobic conversion of ammonia into nitrate, the core chemical process asked about.
High-yield for environment and ecology questions because it explains how toxic ammonia is transformed to less toxic nitrate in ecosystems and engineered systems. Connects to water quality, aquaculture management, and biochemical cycles; useful for questions on pollution control and ecosystem functioning.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 19: Ozone Depletion > The escape ofN,O > p. 269
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > s r n r u l z N ,- / & f . -. : : u ' , \ S ACADEMY * d 6 # . , r '' t u f Y l ' ' J * w { d ) / u Y . / > p. 20
Microorganisms mediate key nitrogen transformations including fixation, nitrification and denitrification between ammonia, nitrite, nitrate and elemental nitrogen.
Fundamental concept across ecology, agriculture and environmental science sections; mastering it helps answer questions on soil fertility, waste treatment, and nutrient cycling. Enables linkage-type questions on ecosystem services and pollution mitigation.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > c) The Nitrogen Cycle > p. 19
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > s r n r u l z N ,- / & f . -. : : u ' , \ S ACADEMY * d 6 # . , r '' t u f Y l ' ' J * w { d ) / u Y . / > p. 20
Ammonia and nitrate concentrations in water influence algal growth and aquatic health, creating management issues relevant to aquaculture.
Important for questions on water pollution, eutrophication and fisheries management; ties chemical forms of nitrogen to environmental impacts and policy responses. Useful for case-based questions on inland water resource management.
- Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > Water Pollution > p. 33
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > Inorganic Nutrients > p. 53
Phosphorus is a central inorganic nutrient that controls aquatic productivity and can drive algal blooms when enriched.
High-yield for environment and ecology questions because phosphorus links biogeochemical cycles, eutrophication, and water quality issues; connects to topics on nutrient limitation, algal blooms, and aquatic food webs. Mastering this enables answering questions on causes and ecological consequences of nutrient enrichment.
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 2: Functions of an Ecosystem > a) Phosphorus Cycle > p. 20
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 4: Aquatic Ecosystem > 4.4.r. What are the causes of these blooms? > p. 39
- Environment, Shankar IAS Acedemy .(ed 10th) > Chapter 14: Marine Organisms > Nutrients > p. 207
Biofloc Technology. In RAS, autotrophic bacteria convert Ammonia to Nitrate (waste). In Biofloc, heterotrophic bacteria convert Ammonia into microbial protein (flocs) which fish eat (food). Expect a comparison question on RAS vs Biofloc mechanisms.
Use 'Functional Etymology'. 'Bio-filter' implies a biological process (bacteria/enzymes) acting on dissolved molecules. 'Uneaten fish feed' is a macroscopic solid object. In engineering, you don't use bacteria to eat large chunks of solid food instantly; you use a physical sieve (mechanical filter). Thus, Statement 1 is functionally mismatched.
GS-3 Agriculture & Food Security: RAS is a critical solution for 'Land-less Aquaculture' in urban areas and water-scarce regions. It also links to Antimicrobial Resistance (AMR)—closed systems like RAS significantly reduce the need for antibiotics compared to open pond aquaculture.