Current Research in Wastewater Management

Iron is one of the most abundant element contained in the ground water. It is mostly present in the form of Iron (II), Iron (III) and metallic Iron in a negligeable quantity. When crossing the delivery network, a ground water may severely destroy it if any treatment is provided. The list of the treatment is very large: aeration, precipitation, insolubilization, cascading, filtration, reverse osmosis and adsorption.Full article

The paper discusses that outside the city of Dilijan, the hydrochemical parameters of the Agstev River increase 1.3-2.6 times. This fact can be explained as the city wastewater of Dilijan enters the river without treatment. Discusses that the pollution of household wastewater is mainly due to the flushing of toilets, kitchen and cleaning water polluted with bacteria, viruses, washing and cleaning agents including dirt and rests of food. The amount of pollutants from the municipal wastewater of the city of Dilijan, which gets into the Agst River per day, has been calculated. The calculation shows that the concentrations of phosphates, ammonium nitrogen, total nitrogen, BOD5 value are close to its real value. It was found that the amount of Suspended substances is less than the real values, which is caused by the pollution of the river by surface waters coming from fields outside the city of Dilijan.Full article

Textile wastewater is considered as the most polluted of all industrial sectors, both from the amount produced and the effluent composition. Most of the previous researches concentrates on extracting dyes from water in a single solution. In real applications, the colored effluents contain more than one removable component. In this study, the adsorption of two textile dyes (Acid Red 1 and Brilliant Green) was investigated in a binary mixture. An adsorbent coating with zwitterionic interfaces was introduced as a new approach for wastewater treatment, named as zwitterionic adsorbent coating (ZwitAd). The derivative spectrophotometry for each dye was used to determine the precise wavelength. Consideration was given to the effect of pH, contact time, initial dye concentrations, and temperature. The findings show that the ZwitAd has a strong potential to simultaneously remove both dyes. Equilibrium was achieved within 300 min and to obtain a higher percentage removal of Acid Red Brilliant Green, ARBG, the optimal condition has been achieved. The higher percentage removal for AR1 and BG was reported at 92.14% and 90.18% respectively at 10BG-40AR (ppm) initial concentration.Full article

Among natural materials, clays occupy a prominent position being low cost, available in abundance, environmentally friendly, and having good adsorption properties. Bentonite, which has strong affinity towards cationic dyes such as methylene blue (MB) is able to remove dye effectively. It is very economical if the spent adsorbent can be recovered and reused for many cycles. Hence, this study investigated the ability of sodium persulfate (Na₂S₂O₈) (SPS) to regenerate bentonite loaded with MB. The modification of raw bentonite with SPS was also investigated. The results showed that after added with SPS, the bentonite and MB adsorbed and flocculated together to form large flocs that were firm and compact. The process adsorption and flocculation was very efficient and equilibrium was reached within one hour. However, the modification of raw bentonite may not be a good option as the flocs formed were loose and less compact. High water retention of the flocs would cause disposal issue during dewatering process. The flocculation mechanism of MB-loaded bentonite can be explained in macroscopic and microscopic level. In macroscopic level, charge neutralization and bridge formation are the main mechanism while in microscopic level, increase in interlayer spacing and extensive cation exchange with MB are the one that contribute to flocs formation. Besides that, dimerization and trimerization also contribute to total MB adsorption which also allow bigger flocs formed. However, the ability of SPS to degrade MB adsorbed to bentonite through oxidation process does remain uncertain. Instead of regeneration, flocculation of MB-loaded bentonite upon addition of SPS occurred to remove the dye effectively. For reusability study, the MB-loaded bentonite can be used up to 3 cycles with percentage removal of 95%. Hence, SPS, as a flocculation promoting agent can be further studied and investigated, to be used in large scale in colour wastewater treatment.Full article

Owing to rapid population growth accompanied by urbanization and industrialization, waste management is an essential aspect of today's world. During 2013, total municipal solid waste generation in Sri Lanka was recorded as 10,768 tons per day, while total municipal solid waste collected was only 3,458 tons per day. Meantime, the organic fraction of municipal solid waste (OFMSW) produced in 2012 was 1,301.5 tons per day. The most widely practiced waste disposal method in Sri Lanka is currently open dumping, which is not an ecofriendly approach. Biowaste, which accounts for about 59% of MSW collected in Sri Lanka, consists of 65 percent of moisture, and valuable resources such as energy, nutrients, and minerals can be readily recovered. Resource recovery, which is linked to the circular economy, is a sophisticated technique of biowaste management. However, resource recovery principles for the local communities in Sri Lanka are fairly novel. The ultimate outcome of this study is to lay the foundation for the development of an autonomous integrated circular system integrated with the existing waste management framework in Sri Lanka, and thus allowing to circulate the vital resources needed to sustain human life in the form of energy, food, and water. Types of resources, which can be extracted from OFMSW are nutrients such as nitrogen and phosphorous, energy, and water from moisture content. Energy can be harnessed as biogas via the degradation of organic compounds in anaerobic reactors, whereas nutrients can be harnessed by converting anaerobic sludge into inorganic fertilizers. The proposed integrated standalone circular system should be able to produce energy via combined heat and power plant and produce struvite via fertilizer production plant. Based on currently available data from 2012, potential electricity generation is 10.31 W per kg of OFMSW, and minimum struvite generation potential is 3.839 g per kg of OFMSW. Excluding the operation and maintenance expenditure and depreciation cost, forecasted revenue from electricity generation and struvite production are respectively is 21,155,926 USD per annum and 455,926.84 USD per annum. Therefore, resource recovery is a socio-economically and environmentally viable waste management practice in the Sri Lankan context.Full article