Lagoon Wastewater Denitrification via Effluent Recirculation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Wastewater lagoon systems face challenges in meeting stringent ammonia and total nitrogen discharge limits due to conflicting requirements for nitrification and denitrification processes, which are difficult to achieve simultaneously, especially in lagoon-based systems.
Innovation Solution
The method involves mixing processed effluent water with influent water and introducing it into the lower, oxygen-poor regions of the lagoon to promote denitrification, utilizing existing infrastructure and minimizing additional equipment, thereby achieving efficient conversion of ammonia to nitrate and subsequent denitrification to nitrogen gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If nitrification is performed to convert ammonia to nitrate, then ammonia levels are reduced, but total nitrogen increases and dissolved oxygen is consumed
Solution Approach 1:
The treatment process is divided into two distinct stages: a first anoxic lagoon for denitrification and a second aerated lagoon for nitrification. This segmentation allows each stage to optimize its specific function without interference, converting ammonia to nitrate in the second stage while removing nitrate in the first stage through the recirculation of nitrate-rich effluent
Solution Approach 2:
Nitrate acts as an intermediary substance that is produced in the nitrification stage and then consumed in the denitrification stage. The recirculation system transports this intermediary between stages, enabling the overall removal of total nitrogen by converting it from soluble forms to nitrogen gas
2Quantity of substance
If denitrification is performed to remove nitrate, then total nitrogen is reduced, but dissolved oxygen levels increase which inhibits the denitrification process
Solution Approach 1:
The system separates denitrification and nitrification into different lagoons with different oxygen conditions. The first lagoon maintains anoxic conditions for denitrification, while the second lagoon provides aerobic conditions for nitrification, eliminating the conflict between oxygen levels and denitrification efficiency
Solution Approach 2:
Instead of attempting to perform both nitrification and denitrification in the same lagoon, the system inverts the approach by using recirculation to move nitrate from the aerated lagoon to the anoxic lagoon, where denitrification occurs under low-oxygen conditions
3Quantity of substance
If a recirculation system is added to enable denitrification, then total nitrogen removal is improved, but device complexity and capital costs increase
Solution Approach 1:
The recirculation pump serves multiple functions: it transfers nitrate-rich effluent from the second lagoon to the first lagoon, maintains appropriate hydraulic flow between stages, and enables the denitrification process. This multi-functionality reduces the need for additional specialized equipment
Solution Approach 2:
The system combines two lagoon treatments (anoxic and aerated) into a single integrated flow path with recirculation, allowing both nitrification and denitrification to occur within the same overall treatment train without requiring completely separate facilities
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows lagoon facilities to meet stricter effluent discharge standards with reduced capital and operating costs, achieving nitrate levels below 10 mg/L without the need for new treatment cells or significant infrastructure upgrades.
Implementation Method 1
denitrification, which requires significant heterotrophic bacteria, BOD to provide a carbon source, and low dissolved oxygen. Under conditions of limited dissolved oxygen (DO), the nitrate reductase enzyme in the electron transport chain is introduced and helps to deliver hydrogen and electrons to nitrate (Metcalf & Eddy), ultimately producing molecular nitrogen (N2)
Implementation Method 2
nitrification, which is a two-step oxidation sequence that first oxidizes ammonia to yield nitrite (NO2) and then, in a separate step, oxidizes nitrite to produce nitrate (NO3)
Data Source
AI summary
In a lagoon-based wastewater treatment process, reduction of total nitrogen in the product water is facilitated by including a denitrification process. In an initial phase of the overall process, raw wastewater is processed in a lagoon to reduce BOD5 and TSS. Nitrification occurs in the lagoon and/or in a distinct or separate nitrification reactor. At least a portion of product water that has been nitrified is mixed with a portion of raw, incoming wastewater, and the mixture is introduced into an anoxic region of the lagoon in a manner that promotes denitrification within the anoxic region of the lagoon.