The effectiveness of chitosan as a flocculant was tested with a novel experimental apparatus. Using a newly developed flocculation tester, a large number of flocculation rate processes were measured. The novel jar tester included a photocoupler and switching timer. Mixing was paused for a period and the floc-settling velocity and residual turbidity were measured during this period. The relation between the turbidity of the supernatant (i.e., the residual turbidity) and chitosan dose was measured over a wide range of initial turbidities. The chitosan showed two windows for the optimum dose: (1) a dose close to that used with ordinary inorganic flocculants, at which the residual turbidity showed complicated behavior under the influence of various factors, and (2) an optimum dose in the order of 10-4 of the initial turbidity. The latter optimum-dose range is very narrow, and simple chargeneutralization plays an important role in the flocculation.

To explore more benefits of flyash in construction industry, a study has conducted on strength characteristics of M30 grade concrete using manufactured flyash coarse aggregate as a partial replacement of natural granite coarse aggregate. The aggregates were manufactured using cement in lesser quantities and flyash in excess quantity various trail mixes were conducted and finally a suitable mix is selected for large quantity production. Cubes, beams and cylinders were casted by partial replacing natural coarse aggregate by 25%, 30%, 35%, 40%, 45% and 50% of manufactured fly ash aggregate. The strength parameters such as compressive strength, flexural strength and split tensile strength of the casted cubes, beams and cylinders were tested respectively.

The complete nitrification process, i.e. complete oxidation of ammonia to nitrate (COMAMMOX), by only one microorganism was experimentally confirmed only two years ago. That discovery is now considered a real breakthrough in the nitrogen cycle in the environment and it opens new questions regarding the nitrogen metabolism by microorganisms. Moreover, it also brings opportunities to revise the approach to nitrogen management in wastewater treatment systems employing the novel nitrogen removal processes, such as deammonification or shortened nitrification-denitrification. The comammox bacteria may significantly disturb nitrite production in partial nitrification, which is the critical step for the successful operation of both novel processes. The crucial role in identification of “comammox“ bacteria is attributed to the latest, advanced molecular techniques (metagenomics and metatranscryptomics).

The aim of this study is the use of local materials (plaster, sand dunes and date palm fiber) for the region of southern Algeria. By expand areas of the use of these materials in the field of construction. Despite the large ament of gypsum, its use is limited to some secondary operations like coatings and decorative elements. The sand dunes and palm fiber, its use in the construction are very limited. In this study, the sand dunes and palm fiber was added to plaster, to find the mortar that has physical and mechanical properties that allow its use in construction. The results obtained showed that the addition of date palm fibers improves the physical properties (density, water absorption, etc.) and mechanical properties (compression strength, flexural strength, etc).

This research focused on the integration of waste plastic into concrete in a bid to restrain water ingress when exposed to water. Polyethylene water sachet (PWS) was the source of waste plastic used. Waste plastic concrete treatments were designed and cast successfully with percentage waste plastic contents of 0, 0.25, 0.50, 0.75 and 1.00. It also involved a constant water/cement ratio of 0.45, a mix design of 1:2:4 and 2% by 342.85kg cement weight of superplasticizer. Twenty cubes, 20 beams and 45 cylindrical specimens were cast for compressive, flexural, split tensile and water absorption tests respectively at 28 days of curing. Waste plastic treatments of 0.5% and 0.75% contents had the highest compressive strength. Water absorption characteristics of waste plastic concrete dropped with increasing plastic waste content to 0.75% after which further increase gave undesirable effects. Optimum water absorption (impermeability) were observed between 0.50% and 0.75% waste plastic content. Waste plastic concrete of 0.75% content with compressive strength and water absorption values of 21.19MPa and 0.22% respectively met the requirements of ASTM C55-11, ASTM C139-11 and CP 102. Waste plastic concrete showed desirable characteristics for potential use in the built environment.

To reduce the consumption of freshwater in the laundry industry, a new trend of separating waste water has resulted in the reuse/recycling of water. In this study, the characteristics of domestic laundry wastewater was evaluated using wastewater samples from four selected laundries. The samples were analysed for the physicochemical and bacteriological characteristics of the water. The parameters examined were: pH, temperature, conductivity, TDS, TSS, turbidity, colour, total hardness, BOD, COD, DO, phosphate, nitrate, chloride and sulphate. The pH of the wastewater ranges from 8.8 – 9.0, TDS ranges from 229 mg/L to 461mg/L, TSS ranges from 228.9–460 mg/L, Turbidity ranges from 25.3– 39.4 NTU and the colour ranges from 4.2-5.8 TCU. The BOD ranges from 144– 211.2 mg/L and the COD ranges from 428.6-531.3 mg/L. The Total Coliform and E.coli in the wastewater ranges from 140-700 CFU. The pH, TDS, colour, total hardness, total coliform and E.coli are within permissible level for toilet and laundry water reuse while TSS, turbidity, BOD and COD exceeds the limit. The result of this study reveals that there is a high potential of recycling laundry waste water for reuse in toilet, irrigation and laundry with little treatment.

Gold mine tailings dams are a high risk part of mining as they contain hazardous materials such as cyanide, mercury and arsenic from processing operations which present a risk to the public and to the environment. When tailing dams fail, the impact is disastrous for humans and the natural environment. The International Commission on Large Dams (ICOLD) collected 221 case records of tailing facility failure incidents worldwide to determine the causes of these incidents. The main causes of these incidents and reported cases of failure were found to be lack of control during the construction, lack of control of the water balance and a general lack of understanding of the features that control safe operations. The important elements to improve the safety and stability of tailings disposal facilities are geotechnical investigation, engineered design, construction, operation and monitoring of the tailings storage facility. Quality engineering is essential in the construction of a fill dam because the materials used have lower strength properties than the concrete dams thus the performance and safety of tailing dam is very important. In this research, the application of Multi Criteria Decision Making (MCDM) methods has been investigated in the Environmental Impact Assessment (EIA) process. For this purpose, Zarshoran Gold mine in the north west of Iran has been selected as a case study. The ability of MCDM methods in EIA has been tested in two parts. In the first part, the best site for dumping tailingss in the case study area has been identified by using TOPSIS method. The weights and criteria are specified to rank the sites and one of the sites has been chosen as the best place in the study area. Results show that the TOPSIS is a powerful method in the EIA process for identifying significance environmental impact and sorting the alternatives.