Graduation Year

2019

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Daniel Yeh, Ph.D.

Committee Member

Norma Alcantar, Ph.D.

Committee Member

Piet Lens, Ph.D.

Committee Member

A. Robert Rubin, Ph.D.

Committee Member

Maya Trotz, Ph.D.

Keywords

anaerobic membrane bioreactor, hydroponics, ion exchange, nitrogen management, zeolite

Abstract

Emerging technologies in sanitation and food production foster the potential to advance progress towards key sustainable development goals of ensuring adequate sanitation and food security to all. Non-Sewered Sanitation Systems (NSSSs), as detailed by the recent International Organization for Standardization’s (ISO) 30500 standard, are being developed to overcome challenges of lacking sanitation infrastructure and resource scarcity by providing autonomous, off-grid wastewater treatment (WWT) service in a much smaller footprints than large centralized treatment facilities. A promising NSSS platform is the anaerobic membrane bioreactor (AnMBR) that can achieve high (WWT) throughput in a small footprint using ultrafiltration (UF) membrane filtration to actively separate solids. AnMBR effluents (membrane permeate), contain high concentrations of nitrogen and phosphorus (N and P) requiring 70% and 80% removal prior to effluent discharge or reuse in non-potable applications (as stipulated by ISO 30500). Ion exchange processes with natural clinoptilolite zeolite perform well at removing total ammonia nitrogen (TAN) from AnMBR permeate because of the low solids, low turbidity, near neutral pH, and high TAN concentrations that are commonly observed characteristics of this waste stream. The regeneration of exhausted clinoptilolite presents challenges of high chemical and energy requirements that can limit the feasibility for implementing these potentially-low cost TAN removal processes.

This research proposes a reusable nutrient recovery system (RNRS), based on natural clinoptilolite zeolite, which releases captured nutrients into adaptive, low-footprint agricultural systems (e.g., vertical hydroponics) to demonstrate reuse of recovered nutrient materials via plant growth. The RNRS was developed to enable recovery and reuse of TAN from AnMBR permeates for fertigation applications that can enhance local socio-economic conditions or food security by providing agricultural fertilizer inputs. The RNRS column prototype reached 10% TAN breakthrough after approximately 30 bed volumes (BV) of synthetic AnMBR permeate solution was passed. Elution of TAN from exhausted RNRS columns revealed that a low, yet constant effluent TAN concentration can be achieved with tap water elution, however roughly 80% of clinoptilolite-bound TAN remained after 120 BV of tap water had been passed. Batches of the desorption solution that resulted from tap water elution were used to cultivate lettuce in vertical hydroponic systems. A short hydroponic growth study demonstrated that RNRS implementation mitigates the effects of inhibitory materials like Na+, Cl-, and dissolved organic compounds that can be deleterious to crop development. A second RNRS bioregeneration study considered recirculation of a fixed volume of tap water eluent solution to facilitate accumulation of nutrient materials released by the RNRS. Recirculation of the RNRS eluent solution was more effective at enhancing the RNRS column TAN release rate and duration. Performance data collected from RNRS testing was used to conduct a sustainability analysis to quantify potential environmental and economic impacts associated with the implementation of the proposed RNRS compared to other possible TAN treatment scenarios deemed suitable for an AnMBR-NSSS application. The proposed RNRS minimized environmental impacts by facilitating reuse of zeolite materials and minimizing chemical regeneration inputs as well as recovering nitrogen fertilizer. While nitrogen removal capacities are well defined, methods for phosphorus recovery and reuse were not fully developed in this work and is an important topic for future research that can enhance the feasibility of the RNRS to integrate WWT resource recovery and agricultural reuse,

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