High - Rate Algal Ponds - HRAPs .pptx

How do HRAPs work?
HRAPs are designed to boost the breakdown of organic waste via algal and bacterial growth and inactivate pathogens via exposure to sunlight.
co-habitation of photosynthetic algae and heterotrophic bacteria is referred to as HRAP symbiosis.
The organic breakdown and pathogen reduction are speed up, which results in smaller retention times in comparison to standard lagoon systems.
The ponds are generally 2 to 3 m wide, 0.1 to 0.4 m deep, and range from 1,000 to 5,000 m2 in area
Theoretical hydraulic retention times (THRT) - The average time that wastewater stays in a treatment tank or system. HRT is calculated by dividing the volume of the tank by the flow rate of the wastewater. Longer HRTs can lead to better quality treated water, but can also cause sludge build-up and increase operational costs. 
Theoretical hydraulic retention times (THRT) are short, between 4 and 10 days, to achieve adequate treatment.

1. HIGH-RATE ALGAL PONDS (HRAPs) Ms. M. Arthi Assistant Professor

2. Waste water

3. PHYCOREMEDIATION The term phycoremediation was coined by John (2000) It refers to the remediation of water carried out by algae. Microalgae have high efficacy in wastewater treatment and can offer possible solutions for environmental problems Microalgae are eukaryotic, autotrophic microorganisms that can adapt to almost any aquatic environment (including wastewater) and produce biomass rich in various nutrients and minerals. Microalgae vary greatly in protein (10% to 53%), carbohydrate (10% to 16%), lipid (15% to 55%), and mineral (5%) constituents

4. Phycoremediation of wastewater (domestic or industry) refers to any large-scale utilization of (desirable) microalgae for the removal of pollutants or biotransformation of hazardous or harmful organic chemical compounds to nonhazardous end-products, xenobiotics, and removal of pathogens from wastewater. Biomass consumes considerable amounts of nutrients from freely available sources, such as wastewater rich in organic nutrients, inorganic chemicals, and CO2 from waste and exhaust streams, that can accelerate the microalgal biomass propagation (45% to 60% microalgae by dry weight), nucleic acids, and phospholipids. Nutrient removal can be further increased by ammonia stripping or phosphorus precipitation due to the increase in the pH associated with photosynthesis

5. Phycoremediation is a biological tertiary treatment, performed typically to treat secondary municipal wastewater. High-rate algal ponds (HRAPs) for wastewater treatment are very effective. HRAP-cultivated microalgal cultures can assimilate huge amount of nutrients, resulting in a reduction in BOD and chemical oxygen demand (COD). Microalgae are regarded as the most versatile solution among biological wastewater treatment processes. Domestic wastewater contains the majority of nutrients such as nitrogen and phosphorous that directly and indirectly support microalgal productivity and maintain the biomass at levels high enough to achieve nutrient removal efficiently in wastewater systems.

6. Application and advantages of phycoremediation Nutrient removal from both municipal and industrial wastewater or effluent enriched with high organic matter Nutrient and xenobiotic compound removal with the aid of algae-based biosorbents ( biological material that is used to remove pollutants from water and other solutions ) Efficient treatment of acidic and heavy-metal wastewater Increase the oxygenation of the atmosphere CO2 sequestration Improve the effluent quality Transformation and degradation of xenobiotics Biosensing of toxic compounds by algae

7. ALGAE SPECIES USED FOR PHYCOREMEDIATION Phormidium - isolated from a polar environment below 10°C, and the capability of this strain to remove inorganic nutrients in wastewater during spring and autumn of cold climates. Common microalgae in wastewater treatment include Chlorella – universally grown Chlorella species (vulgaris) Oscillatoria, Scenedesmus, Synechocystis , Lyngbya , Gloeocapsa , Spirulina, Chroococcus , Anabaena , and others Botryococcus braunii , - used for primary treated sewage waste Scenedesmus obliquus - used in the treatment of urban wastewater

8. G eneral types of maturation ponds employed in wastewater treatment

9. What is a High Rate Algal Pond? High-rate algal ponds, also called HRAPs, are shallow raceway ponds that move wastewater via a low-power paddle wheel. They are typically used in two scenarios: To treat high-strength wastewater To grow algal biomass for biofuel production.

10. How do HRAPs work? HRAPs are designed to boost the breakdown of organic waste via algal and bacterial growth and inactivate pathogens via exposure to sunlight. co-habitation of photosynthetic algae and heterotrophic bacteria is referred to as HRAP symbiosis . The organic breakdown and pathogen reduction are speed up, which results in smaller retention times in comparison to standard lagoon systems. The ponds are generally 2 to 3 m wide, 0.1 to 0.4 m deep, and range from 1,000 to 5,000 m2 in area Theoretical hydraulic retention times (THRT) - The average time that wastewater stays in a treatment tank or system. HRT is calculated by dividing the volume of the tank by the flow rate of the wastewater. Longer HRTs can lead to better quality treated water, but can also cause sludge build-up and increase operational costs.  Theoretical hydraulic retention times (THRT) are short, between 4 and 10 days , to achieve adequate treatment.

11. Mixing is achieved using a low-power paddlewheel , which circulates the wastewater through the channels. Operated at velocities of 10 to 30 cm s−1. Continuously mixing the wastewater avoids thermal stratification and maintains a homogenous chemical environment throughout the channels. This environment helps to maximize the breakdown of organic waste and removal nutrients via algal and bacterial growth. Microalgae assimilate nitrogen and phosphorus from the waste water that can be recovered from the algal biomass for reuse. The shallow depth combined with mixing helps to maximize pathogen inactivation via sunlight

12. HRAP design Selected based primarily on the site topography. The two most common configurations Single loop configuration Serpentine channel configuration

13. Algal species used The efficiency of nutrient removal depends on the species of algae cultivated. Algal strains that are tolerant to certain extremes, such as extreme temperatures, quick sedimentation, or the ability to grow mixotrophically. Chlorella vulgaris, Haematococcus pluvialis , and Arthrospira (Spirulina) platensis , - species that can grow under photo-autotrophic, heterotrophic, and mixotrophic conditions

14. Choosing a strain for cultivation in HRAPs (1) have a high growth rate, (2) have a high protein concentration when grown under nutrient-limited conditions, (3) be used for animal/fish feed, (4) have the ability to tolerate high nutrient levels, (5) produce a value-added product, (6) be able to grow mixotrophically, and (7) be easily harvested

15. Nutrient removal Phosphorus removal of 98% and total ammonia removal has been achieved by using Scenedesmus obliquus . R emoval of nitrate and phosphate to 2.2 mg L−1 and 0.15 mg L−1, respectively, using microalgal biofilms. Certain photosynthetic bacteria and green microalgae such as Rhodobacter sphaeroides and Chlorella sorokiniana can, under heterotrophic conditions, remove high concentrations of organic acids (>1,000 mg L−1) and ammonia (400 mg L−1) The bacterial removal of substances such as polycyclic aromatic hydrocarbons, organic solvents, and phenolic compounds may be assisted by the use of microalgae that produce the oxygen required for bacterial action. Heavy-metal biosorption may be achieved by microalgae grown under phototrophic conditions

16. Factors Affecting High-Rate Algae Ponds

17. WASTEWATER AS FEEDSTOCK FOR BIOMASS PRODUCTION Wastewater treatment using HRAPs has the potential to produce large amounts of biomass that can be used for a variety of applications, including the production of renewable fuels, fertilizer, animal feed, etc. use of wastewater as a substrate for biofuel production may make the process economically viable Microalgal biomass to biofuels conversion may be carried out by several methods depending on the biomass characteristics (e.g., lipid or carbohydrate content) The yields of biomass from HRAPs depend on the type of effluent being treated with specific regard to nutrient content. Maximum algal productivities in HRAPs can be achieved by countering rate-limiting and inhibitory conditions. Carbon is often a rate-limiting substrate and may be alleviated by the addition of CO2. However, it must be considered that addition of excess CO2 leads to a decrease in pH.

18. Advantages of HRAP HRAPs have been used for the treatment of a variety of wastewaters, including domestic wastewater, piggery and animal wastewaters, agricultural runoff, and mine drainage and zinc refinery wastewater. These systems are simple to operate when compared to conventional technologies, thus making them ideal for use by small rural communities . High-rate algal ponds are sustainable, low-energy and low-cost alternative wastewater treatment options. They take only 4-10 days to treat wastewater, compared to a conventional system that requires 66 days to treat wastewater. Superior Ammonia Removal: HRAPs achieve better ammonia reduction (59-74%) compared to facultative ponds . using Scenedesmus obliquus Lower Power Requirements: HRAPs consume less energy than mechanical treatment plants (e.g., activated sludge, Membrane Bioreactor - MBR, etc.).

19. HRAP's ability to remove pathogens is equal to, or better than, existing wastewater systems. Cost about 40% less to construct compared with conventional lagoon systems. Shorter retention times of between 4-10 days for effective treatment result in a smaller carbon footprint and reduced evaporation by approximately 12-30%. Minimal operator intervention is needed when instrumentation and alarms are installed. The paddle wheel means low power consumption and a lower carbon footprint. Better public health outcomes and ensure effective management of public health risks.