Community Waste Management Systems usually consists of an optional lagoon or mechanical treatment plants (such as Sequencing Batch Reactor). Treated water is stored in storage lagoons during the winter or disposed of via irrigation or evaporation lagoons. Both treatment options have their strengths and weaknesses and we have to choose the most efficient system.
New type to algal ponds are devised to treat wastewater which is discussed in the given blog.
What is High Rate Algal Ponds and benefits?
High Rate Algal Ponds (HRAP) is a low-cost, nature-based technology that can be successfully deployed where weather conditions are suitable for the growth of microalgae (egg, high solar irradiance and temperature). They consist of shallow ponds with gully where microalgae can grow and consume nutrients that are still present in the water supply (poor quality water such as sewage).
HRAP is designed to maximize the breakdown of organic waste by the growth of algae and bacteria and to inactivate pathogens by exposure to sunlight .Micro-alga’s also release oxygen during photosynthesis, which heterotrophic bacteria uses to oxidize and break down organic matter. This symbiosis leads to the production of clean water as a by-product, as well as the growth and production of algal biomass.
Algal biomass is further stabilized, processed and bio-energy is (biodiesel and/or biogas) or bio-fertilizer is released. Other benefits such as the production and intracellular accumulation of various value-added products that can also be obtained from microalgae under certain growth conditions, such as glycogen, bio-plastics, lipids and terpenoids were recently announced.
Accelerated organic degradation and pathogen reduction result in shorter residence times compared to traditional lagoon systems. The dwell time is 4-10 days and the depth of the pond is usually 300-500 mm.
Here are some of the reasons why HRAP is suitable:
1: HRAP reduces pathogens by at least one logarithm and improves public health results.
2: Shallow depth of 300-500 mm.
3: Construction cost reduced by 40% compared to traditional lagoon systems.
4: Paddle wheel with low power consumption and carbon dioxide emissions.
5: Reduces residence time of 4-10 days for effective treatment, reduces footprint and reduces evaporation by about 12-30 %.
6: Minimal operator intervention is required if instrumentation and alarms are installed.
7: Limited energy available.
8: Limited land area.
9: High evaporation rate due to climate.
10: Limited access to experienced operators.
Process of Treatment and Basic Design Principles
1: Advanced Facultative Pond (AFP)
Advanced facultative ponds consist of a conventional facultative pond containing a fermentation or digester pit on its bottom. Sewage entering the system is injected at the bottom of the digester pit, where solids are trapped and consumed by anaerobic digestion producing methane. The most attractive feature of AFPs is their high capability of wastewater total suspended solids (TSS) removal, in addition to BOD removal. The facultative pond is about 4 to 5 m deep. The surface aerobic layer is about 1 m deep and helps reducing potential odour problems. Biogas may be collected using a submerged gas canopy and can potentially be used for energy production.
2: High Speed ??Algae Pond (HRP)
Water from the facultative pond flows into a high-speed pond where aerobic bacteria isdissolved, which absorbs organic matter and algae absorbs nutrients and other bodies. HRPS is designed to promote the symbiosis of microalgae and aerobic bacteria using each other's major metabolites. Microalgae grow large from photosynthesis in water. They release oxygen in photosynthesis. This oxygen is readily available for bacteria to oxidize most of the soluble, biodegradable matter remaining from the pond. HRP is shallower than the pond and operates with a shorter hydraulic retention time (HRT). With the rapid growth of algae, the pH can exceed 9 as carbonate and bicarbonate react at peak levels of algae activity to supply more carbon dioxide to the algae and leave excess hydroxyl ions.
Normally, an outer ring is attached to propel water around the racetrack-shaped pond. When algae supersaturates a high-performance pond with oxygen, some of the water from that pond is returned to the top layer of the optional pond, increasing its oxygen content, thereby reducing or eliminating the need for mechanical aeration.
3: Mature Pond (MP)
These ponds are the final step. They are traditional mature ponds commonly used in other pond systems such as the Waste Stabilization Ponds (WSP). The treated water is exposed to the sun and wind, resulting in natural oxygenation and disinfection by the sun, thereby inactivating pathogens.
HRAP treatment can be considered one of the most ecologically and economically advantageous treatments due to its lower energy requirements and lower cost compared to traditional activated sludge systems. These are suitable solutions for wastewater treatment, especially in less populated areas, as they reduce the costs and environmental impact associated with wastewater treatments.
What can Netsol Water provide?
Netsol is India’s leading wastewater treatment solution company which covers all the needs of any water and wastewater treatment scheme on all levels. We have the expertise to provide waste water solutions at domestic, industrial and municipal level.
Contact us for consultations as well as to clear up all your queries about wastewater and its treatment process, methods and cost optimisation in construction and management of the treatment systems.