1. Environmental monitoring for perchlorate (rocket fuel) contamination
Perchlorate (ClO4-) is an emerging environmental contaminant, known to interfere with the functioning of human thyroid gland leading to hypothyroidism. Infants and pregnant women are the most vulnerable group to this chemical. Perchlorate is mainly used (as ammonium salt) in rockets, missiles, explosives, match box industries etc.
As per US EPA guideline, perchlorate concentration at 15 ppb (ug/L) in drinking water is NOT expected to cause any adverse health effects. The ongoing research at Environmental technology lab in NIIST mainly focuses on (1) assessing the level of perchlorate in drinking water in Kerala and other states and (2) to find relations (if any) on increased incidence of hypothyroidism where high environmental contamination of perchlorate was observed.
Perchlorate concentration several thousand magnitudes higher than International guidelines were found in ground water samples from few locations in Kerala. Severe contamination (>40,000 ppb) was found in ground water samples around the ammonium perchlorate manufacturing unit in Keezhmad in Aluwa (Ernakulam district, Kerala). We have screened around 200 wells in the area and spatio-temporal distribution of perchlorate was monitored. The important information was shared to the State health dept.
Figure; Ground water perchlorate profile during 2014-15 at Keezhmad in Ernakulam dist.
Subsequent study by the State health Dept. revealed nearly 80 people including children were hypothyroid (high TSH levels) in the contaminated area. We provided technical support to the State health department and local self-government to tackle the situation. Based on our suggestion alternate drinking water was provided to the affected area. Nearly 90% people recovered from hypothyroid condition to normal in three-month period.
Our intervention helped the recovery of many people from a serious health problem and presented large number of people getting affected.
2. Microbial bioprocess for perchlorate decontamination
Perchlorate is a highly persistent contaminant emerging endocrine disrupting contaminant. The usual physico-chemical pollutant removal methods like adsorption or chemical reduction are not techno-economicaly feasible. But engineered biological systems employing perchlorate reducing bacteria can decontaminate perchlorate into non-toxic chloride and oxygen.
At NIIST we have developed a microbial system capable of reducing perchlorate. Lab scale studies have completed using synthetic and real effluent from industries. Real effluents from local ammonium perchlorate consuming and manufacturing units (ISRO-VSSC) were treated in the lab using the microbial system.
Several bacteria capable of reducing perchlorate was isolated in pure and molecular characterization of the novel cultures was done and nearly 30 gene sequences were submitted to GenBank.
Figure : Whole cell FISH image showing perchlorate reducing bacterial cells
The lab-scale findings were translated into a bioprocess (Patent filed) for perchlorate contaminated water as well as soil (ex-situ soil remediation).
The treatment study was conducted in pilot scale bioreactor (140 lit) unit. The bioreactor removed (98%) perchlorate at 10 mg/L level at very low HRT of 4.5 hrs.
The soil remediation system is a two stage process where the perchlorate will be completely leached out with tap water and the perchlorate containing tap water will be regenerated in a bioreactor. The treated water will be used again for another contaminated soil lot. This will be continued many times. The unit was demonstrated in a 670 kg soil lot (1 M soil height).
The developed processes were demonstrated to stakeholders like local self-government officials in the contaminated regions, state/central ground water dept. etc.
3. Integrated Bio-physical process for generating potable water from rocket fuel contaminated ground water:
An integrated bio-physical process was developed for generating safe drinking water from perchlorate contaminated ground water. This process is developed especially for communities in the perchlorate contaminated regions.
The integrated unit consists of a bioreactor for reducing perchlorate in ground water to almost nill (98% removal). The residual organics and microbial load will be removed in a combined micro-filtration and RO unit. The final water will be without any perchlorate (from initial 10,000 ppb). The demonstration scale unit able to generate ar ound 200 L per day drinking water
4. Biomethanation of food waste through dry digestion (high solid treating digester):
Bio-methanation of food waste through anaerobic digestion is a widely accepted practice. However, the conventional digester (vertical) has inherent limitation such as it needs equal volume of water along with the waste, it cannot treat food fractions like egg shell, lemon, onion peel etc., it provides mosquitoes breeding grounds etc.
With this background, a new digester design is formulated working under dry digestion or high solid content. The major advantages of this process unit it compact size, does not need water along with food waste, it can treat any food waste, no mosquito problem, it generates more biogas with high methane content, less slurry out, etc.
It can comfortably treat solids up to 5-6 Kg dry solid/M3/day. The biogas yield will be nearly 150-170 Lit/kg food waste with >60% methane. The retention (HRT) time will be around 40-50 days. WE have installed different capacity digesters (5-50 kg food waste/day) in the field.
Figure: Compact house hold biogas unit for recovering food waste and cow dung.
5. Ecological Niche of higher trophic organisms in anaerobic bioreactor:
In addition to Bacteria and Archaea, anaerobic environments including wastetreating bioreactors and natural environments, higher trophic organisms like protozoa and micro-metazoa (micro-animals) also inhabit these habitats. The ecological niches occupied by these organisms have functional importance in the overall functioning of the reactor. Many anaerobic protozoa inhabit waste treating bioreactor and plays significant role such as intracellular digestion of complex organics, nutrient recycling and biomass reduction through grazing activity and harbour endo-symbiotic methanogens. The ongoing research focuses on the diversity and population dynamics of higher trophic organisms and to analyze their functional importance in waste treatment.