Q: What might be a selling point for a major city like Chicago to risk its world class city status to move in this direction?
Any new sanitation system must satisfy the users and be appropriate to the context. The challenge is for scientist, engineers, planners, waste water treatment companies, governments, etc to develop sanitation systems that meet existing levels of service and satisfy the challenges faced by the waste water industry (water shortages, rising costs of energy and chemical inputs, aging infrastructure, treatment plant site contrainsts,etc). The end vision may be a generation away but we need to start now.
Q: How feasible is it to retro fit so many processes as outlined in Tony's PFD with the current ecenomic climate and limited funding available?
A: Design of sanitation systems are context dependent and the viability of such resource recovery technology will depend on many factors. The presentation was not suggesting all STP's be retro-fitted but rather for designers, and water utilities to consider the potential of nutrient recovery for where it meets certain drivers. Further R&D is necessary.
Q: Having used eco / waterless toilets in the Maasai Mara in Kenya and Chumbe Island Zanzibar, one of the issues is odour and how to clean these toilets. Does the use of detergents/toilet cleaners affect effectiveness of nutrient recovery?
A: Strong detergents may interfere with biological processes. Odours can be prevented with adequate constructional measures and maintenance.
Q: Is this accounting method for valuing utilities being used around the world?
A: The accounting method outlined in the presentation is a way for utilities to justify nutrient recovery technology and demonstrates that viability will be context specific.
Q: What benefit for reuse is nitrogen gas from electrolysis?
A: Production of nitrogen gas is only beneficial from a removal point of view. Our research examines how oxidation can be halted at nitrate stage, to recover nitrate from the process.
Q: Can the ammonia distilate be discharged to the environment? Or does it need additional treatment to remove the ammonia
A: Depends on regulations. Distillate may be used e.g. to flush toilets. Ammonium can be completely removed via electrolysis of the distillate.
Q: Can Vuna be coupled with micro Algea process for CO2 absorption?
A: Various projects have been carried out to test algeal growth with urine as fertilizer. We have cultivated lemna species in urine fertilized water, with positive results.
Audience Question:
Q1: Int´t nitryfiny very energy consuming? Q2: Does nitrification suffer inhibion due to the high ammonia concentrations?
A: Energy consumption of urine nitrification and distillation roughly equals consumption of conventional wastewater treatment and Haber-Bosch process for fertilizer production.
A: Yes - 3 to 4 kWh per kg of ammonia oxidised
A: stored urine is added gradually to keep concentrations under control.
Q: Given how hard it is to convince developers to segregate black and grey water - how viable is yellow water segregation and is it completely neccesary to recover the urine minerals?
A: Social aspects have to be integrated into the project right from its inception. The UD toilets in our office building have been operable since 2005 without any major problems. By avoiding dilution with flush water, we are able to recover minerals in a more efficient way.
Q: What is black water?
A: the water coming out of toilets, containing excreta and flush water.
Q: Does there need to be solids removal protection before resin treatment? Does there need to be BOD removal to protect from biological growth within the resin
A: BOD contained in urine is removed by about 90 % during storage and nitrification. Further experiments will determine, how the remaining 10 % can be eliminated. Primary clarification is usually enough. biological growth is usually limited by regeneration conditions
Q: Is the resource recovery process design - energy neutral? or do you need more energy into the system?
Q: Are any of the ammonia recovery technologies installed on a commercial scale?
Audience Comment - improved material use in toilet construction would mitigate the frequency of cleaning, i.e. slippery porcelin'
