Development of photochemical integrated submerged membrane bioreactor for textile dyeing wastewater treatment.

A pilot-scale photocatalytic membrane bioreactor (PMBR) was developed for the treatment of textile dyeing wastewater. The PMBR is made of mild steel rectangular reactor of photocatalytic unit and polyethersulphone submerged hollow fibre membrane bioreactor unit with the working volume of about 20 L. For easy recovery, the tungsten oxide (WO3) and WO3/1% graphene oxide (GO)-powdered photocatalyst were made into bead and immersed in photocatalytic reactor. Graphene oxide incorporation has shown better results in decolourisation and degradation when compared with WO3 alginate alone. The incorporation of GO into WO3 minimises the recombination of photogenerated electron-hole pairs. The operating conditions such as 3 h of contact time for photocatalysis reaction (WO3/1% GO), 10 h hydraulic retention time for MBR and 100 kPa of transmembrane pressure were optimised. Chemical oxygen demand removal efficiency of 48% was attained with photocatalysis, and the removal efficiency was further increased up to 76% when integrated with MBR. The colour removal efficiency after photocatalysis was 25% further increased up to 70% with MBR. Complete total suspended solid removal has been achieved with this hybrid system.

Evaluation of chromium in vegetables and groundwater aptness for crops from an industrial (leather tanning) sector of South India.

The main objective of the present study is evaluation of groundwater aptness for crops and chromium concentration in vegetables from an industrial (leather tanning) sector of South India using geospatial techniques. Seventy groundwater samples were collected from the open and tube wells during November 2017, February 2018, May 2018 and September 2018 to represent northeast (NE) monsoon (October-December), post-monsoon (winter) (January-February), pre-monsoon (summer) (March-May) and southwest (SW) monsoon (June-September) seasons, respectively. In addition, vegetables were also collected during the above-mentioned seasons from the market to assess the level of chromium content in them. All the groundwater samples were tested in the chemical laboratory using the American Public Health Association norms for various physicochemical parameters, viz. TDS, pH, sodium, potassium, calcium, magnesium, bicarbonate, chloride, sulfate, nitrate, fluoride and chromium. Northeast and southwest monsoon season samples mostly represented 'high to very high saline' and 'low alkaline' categories of irrigation water. However, post- and pre-monsoon samples represented 'high to very high saline' and 'low to medium alkaline' categories. 'High saline and low alkaline' water could be used for irrigation in all types of soil with less problem of exchangeable sodium. However, 'very high saline' water should not be applied for the crops having poor salt tolerance and soils having poor internal drainage. The concentration of chromium in groundwater and vegetables was within the permissible limits for human intake prescribed by the World Health Organization standards.

Evaluation of advanced oxidation processes (AOPs) integrated membrane bioreactor (MBR) for the real textile wastewater treatment.

A novel submerged membrane bioreactor integrated with ozonation and photocatalysis has been developed to treat the real textile wastewater and study the fouling behaviour. This study evaluates the performance efficiency in pilot-scale for the three reactors such as membrane bioreactor, ozonised membrane bioreactor and further clubbed with photocatalysis. The membrane filtration consists of polyvinilidine difluoride hollow fibre membrane module having pore size 0.1 µm. Tungsten oxide, a visible photocatalyst was made into spongy alginate beads and used in photocatalytic reactor. The photocatalyst dose has been optimised as 500 mg/L. About 10% membrane filterability ratio has been achieved by integrating ozone with MBR with the maximal ozone dosage of 5 g/h. It showed better removal efficiency in colour and chemical oxygen demand of 94% and 93% respectively. The biodegradability efficiency also was enhanced from 0.2 to 0.4 with optimised ozone dosage (5 g/h). The study on reversible and irreversible fouling has been done to understand the fouling nature. The important analysis such as microbial community and scanning electron microscopy analysis were done to study the biofouling and extent of fouling after filtration. The treatability studies implemented for textile wastewater showed that integrated MBR systems are suitable in meeting the discharge norms prescribed by the Indian statutory body in terms of chemical oxygen demand, colour and total suspended solids.

Impact of precipitation disparity on groundwater fluctuation in a semi-arid region (Vellore district) of southern India using geospatial techniques.

In the present study, impact of precipitation disparity on groundwater level fluctuation was carried out in Vellore district, Tamil Nadu, India, using geospatial techniques. There are five rain gauge stations in the study area in which three rain gauge stations, namely Alangayam, Jolarpettai and Pernampet, receive more precipitation when compared with the average annual precipitation of Tamil Nadu state (920 mm). The other two stations, namely Madanur and Natrampalli, receive less than 920 mm of precipitation annually. The overall average annual precipitation of the study area is 913.6 mm. More than 100 mm precipitation is received in all the five rain gauge stations during southwest (SW) and northeast (NE) monsoon seasons. The maximum monthly precipitation is usually recorded during the month of November and the minimum precipitation is recorded during June. The post-monsoon precipitation is around 10.8 mm, which is almost negligible in the study area. The contribution of precipitation by various seasons is in the following sequence: Southwest monsoon > Northeast monsoon > Pre-monsoon > Post-monsoon. The spatial disparity study indicates that the intensity of average annual, pre-monsoon and post-monsoon precipitations increase towards west in the study area. The intensity of precipitation is more in the northern part during SW monsoon season, whereas the intensity is more in the southern part during NE monsoon season. The spatial disparity analysis of groundwater fluctuation shows that the depth of groundwater (below ground level) increases towards west during all the monsoon seasons. The minimum, mean and maximum depths of occurrence of groundwater in this region are, respectively, 1.6, 9.6 and 21.15 m. Declining trend in the regional groundwater level is observed from December to June because of less precipitation during non-monsoon season. However, the monsoon (both SW and NE monsoon) precipitation recharges the groundwater from June to December to reach the maximum in the month of December.